Tire wear, Tire testing and recommendations.
Wheels, spacers, nitrogen, wet roads, hydroplaning, etc.
...for BMW & other Motorcycles.
PLUS things you never knew about tires!
© Copyright, 2014, R. Fleischer
article #54, section 5
It is difficult to maintain a list of recommended tires, due to changes in what is available; and,
have ridden & tested. Up until a couple of years ago, my normal testing was considerably more
vigorous & formal than that of many riders. I am putting on fewer miles these days, and have been
reducing the vigorousness of testing. In the past I had not often included other's remarks about
tires that I had not personally ridden & tested. I now have three people, whose tire testing mirrors
mine close enough. I will include their input now & then. In this article I will clearly state when I
personally have less experience or no experience on a particular tire. I list some discontinued
tires on purpose, for reference & comparison.....some old style tires are now being re-made,
often with updated rubber and possibly construction.
MORE information on wheels is located in: http://bmwmotorcycletech.info/wheels.htm
http://bmwmotorcycletech.info/section6.htm gets heavily into tube & tubeless, on various rims.
http://bmwmotorcycletech.info/tirerepair.htm gets heavily into tire repairs.
Some words of caution, and STRAIGHT TALK:
Some types of tire testing is relatively easy, and this is the type MOST TYPICALLY reported or
commented-on, in Lists, Forums, ETC. This is somewhat TO MORE, simply anecdotal
reporting, and, frankly, mostly it is JUST OPINION, with LITTLE REAL FACTS. This type of
opinion comes from those who do these things (generally):
You keep your tires inflated properly; you ride like you usually do, on paved roads (most riders),
with mixed speeds, mixed type of curves, mixed type of road roughness, mixed loading.
You write down the odometer reading when you put the tires on and when you take them
off for replacement.
Perhaps you always replace tires when the center of the tread is 1/16" deep. You write the
mileage down, subtract, and now you have YOUR typical mileage for YOUR usage on THAT
tire, at YOUR weight, loading & tire pressure. Yes...this can be useful information. But, in
your 'opinions', do you specify EXACTLY all the facts about riding style (in depth), pressures,
loads, types of roads...and many other things. If you say you are aggressive, just what does
that REALLY MEAN? Would you be able to write a report, that not only gives real testing
facts, but recommendations, comparisons against other brands and models, ETC.?
Many are interested, when discussing motorcycle tires, about how well the tire 'sticks to the road';
how well it handles various conditions. In a rather large percentage of instances, no 'standards',
only not-very-qualified opinions, are seen in such discussions. The bald truth (BAD pun!) is that
modern tires are vastly better than the tires were when your Airhead was manufactured (particularly
before the nineties), and unless you have REAL racetrack experience, you are UNLIKELY to out-ride
the tire; in fact you are probably unlikely to know how-to.
Your Airhead is of limited power, limited braking, and may have suspension aging or improper setup
problems...all of which affect tire life (AND handling!).
VERY serious accidents can occur with something as simple as a tight turn, especially at speed,
especially with a rear tire tread that has been worn more than somewhat (the center of the tire tread
is flattened), when it originally was rounded to some degree.
IF you tried to duplicate my style of testing (particularly when I was younger!), and the testing or at
least educated experience from those who ACTUALLY put their tires 'to the test', perhaps on
racetracks, or in serious dirt conditions......you could be asking for serious trouble.
ASK YOURSELF: Are you REALLY competent at crossing up the steering during sliding? Does the idea
of crossing-up the steering freak-you out? On wet roads? What about when your beautifully executed
carving turn encounters lots of bumps? Sudden off-banked tight turns? Washboards?
Can you truly (be honest!) feel the difference a FEW pounds of pressure makes? Have racetrack and
soft dirt/gravel and wet roads experience?
Are you smooth with the controls (including brakes, clutch and throttle)? Are you smooth with transitions
from any surface or turn direction, etc.?
I am NOT so much questioning you here about YOUR REAL COMPETENCE, as I am questioning your tire
testing abilities....and, in particular, your analysis of YOUR tires.
Tires DO vary considerably, in how they handle, how they wear, and under what types of conditions
(including road surfaces, straights, turns, off-banks, braking in dry good friction areas versus wet
roads....what about deeper water on those roads? What type of tire do YOU NEED? WHY? What
characteristics of/in a tire do you REALLY need? Be honest with yourself!
PROBABLY quite a few tires will work well for most any type of riding you do. BUT, you MAY be the
type of rider that really IS aggressive, or has special needs. Perhaps you really do ride off-road, into
seriously soft stuff, mud, single track trails, real Adventure Riding. Perhaps you love carving turns at
speed on paved roads. Are those turns nice sweepers, or really tight twisties on, perhaps, very narrow
roads? Perhaps you REALLY use the front brake truly hard. Perhaps you ARE a real all-weather rider;
maybe you use your motorcycle as your primary transportation, year-round. Riders have different real
needs for their tires.
I will try to cover all uses and rider types for specific tires. Since there is so much interest in tires, I
offer a fair amount of information in this article. I will try to separate anecdotes from facts. I try to
separate those whose input comes from racing experience, from those with road experience. I try to
do that in several ways. Keep in mind that when a very experienced track racer rides a bike on the
streets and highways, his/her expressed viewpoints about their tires tends, often rather strongly, to
be a comparison between how his RACE BIKE handled on a RACETRACK, with REAL racing tires,.....
to what his street bike feels like on street-riding tires. This may/can have NOTHING MUCH OF VALUE
to YOUR, the street rider. BUT, his/her input MAY have very solid value, depending on how his/her
street riding is done. In MY experience, real racers are milder in street riding, than you may think....but,
they ALSO may be VERY aggressive AT TIMES in such as tight twisties. Thus, their input on tire feel
and mileage may be very different from your input, even if you say, and ARE, aggressive in your riding.
Do YOU square off your rear tire in your riding?...do you wear the sides of the tread very noticeably?
How do reports from these various types of riders vary? Why?
I HIGHLY RECOMMEND YOU DO NOT TRY TO DUPLICATE MY PRIOR TESTING METHODS UNLESS
YOU ARE COMPETENT TO DO SO, AND ARE WILLING TO TAKE ON THE RISKS OF DOING SO.
I AM NOT...NOT!!...RESPONSIBLE FOR INCIDENTS/ACCIDENTS!
Most of my testing was done on a variety of Airheads. Some was done on classic K-bikes. In a few
instances, I tested on other folks motorcycles, and, more rarely, on other makes of bikes.
1. Some types of tires do/did not work well on some Airhead motorcycles. Radial tires, quite some time
ago, did not generally come in Airhead sizes; particularly for the twin shock Airheads & early Monoshock
Airheads. Most Airheads were never shod with any type of radial tire. The tires that they came with, and
were shod with later, were more clearly delineated between lower mileage 'stickier' tires & high mileage
tires. Tire characteristics VARIED MORE, IN SOME RESPECTS, THAN TODAY. TIRES BACK THEN
ALSO REQUIRED LOWER TIRE PRESSURES; CONSTRUCTION OF THE TIRE WAS QUITE DIFFERENT
(FOR MANY) THAN TODAY'S TIRES. Now we have special radial tires for 'classic' motorcycles like our
Airheads & the Classic K bikes (K models up to K1200, is what I mean). Most do well, if not excellently.
LOWER profile tires (modest, such as 80 section) may not work well (exceptions, particularly the K bikes),
& many simply don't properly fit old Airheads. Generally a "90" profile works best on all but the very last
Airheads. SOME 80 profile tires will fit & perform OK on earlier Airhead bikes. Unless I specifically make
such note in this article, assume that I used the stock tire sizes, or metric equivalents, or close metric equivalents.
2. The frames & suspensions were designed by BMW for a specific feel and handling that BMW desired. Many
seem to have no idea that frame design and construction, suspensions, and MANY other things, ALL affect
how a motorcycle feels, and one simple word is often used, without specifics: HANDLING. In common use
are such terms as FEEL, TURN-IN, FALL-IN, TWITCHINESS, QUICKER-Handling, and many other words,
that you might think mean something specific.
3. BMW used to issue bulletins with names & models of tires that BMW HAD TESTED & APPROVED;
but that has not been done for Airheads since they were in production (with some exceptions).
4. Here is a link to a rather nerdy article. The article has extensive vector & other diagrams, & some conclusions
about contact forces, that may well astonish you. When you read it, keep in mind what REALLY happens when
you are cornering.....&....THINK....about the effects of you changing a tire size....from, an example here, a 90/90
to a 100/90. What REALLY happens when you go to a larger size tires (larger width). You may be very interested.
5. Many if not mostly all of the tires from the seventies, eighties & nineties, are no longer available, except for a few,
including the classic Continental RB2 and K112, and now some re-incarnations of Metzeler 'Heritage" tires, etc.
Those Continental front tires, unfortunately, follow rain grooves. Rain-groove-following is a problem with all
straight ribbed front tires, and some others too with irregular treads. There are tires available now that have only
one center rib, usually wider than the old narrower grooves; and are typically better on rain grooves. Tires
withOUT center ribs of any sort generally do not usually follow rain grooves, but there are exceptions; usually the
instabilities are mild. Some folks are very much bothered by the feel of their bike when the tires track rain grooves,
other riders are not bothered, simply accepting the feel. SOME types of bridge gratings can cause an even
more disturbing situation, depending on the types of gratings....and can cause a goodly pucker factor;
even increased concern if the gratings are wet from rain. Not many ride on original type of ribbed front types.
They DO, usually seriously, follow rain grooves, contrary to what is said in some Clymer's publications. Still, you
MAY want to try a set, as they can deliver the classic ride & handling that your bike was designed-for; and ...note
here, that these tires generally work best at the originally recommended by BMW tire pressures (label was under
the seat, see your owners manual too), or slightly higher (typically by 2 psi front, 3 psi rear). I recommend that
if you run these classic tires that you inflate to the TWO-UP and/or high speed pressures shown in the Owners
Booklet. BUT, be sure to check the tire manufacturer's recommendations!!! These tires give reasonably good
mileage before they wear out. If you have a modified suspension, the classic ride & handling will be modified.
6. I have personally ridden on quite a few modern tires, besides the really old type tires. MOST road type tires offer
reasonably good road handling, decent predictability of handling in various situations, indication to the rider of what
the tires are doing AND GOING TO DO; as well as comfort, load carrying, traction in cold/wet/dry and not
unreasonable differences in handling between moderately wet & dry. One thing usually discussed, MILEAGE
(tire wear), SHOULD NOT the most important characteristic for most riders ...although for some folks, who put
on large mileages, mileage can be of more importance...so I DO get into recommended tires for mileage. MANY
of today's tires, including re-incarnations of old styles, will have better mileage, than long ago, even though
these modern tires are not being sold as 'high mileage'. That is due to the use of silica's (sand.....), and
different tire compounds in the center and even sides of the tire.
7. There is a wide difference in how tires FEEL to the rider & also wide differences by models of BMW
motorcycle. Trail & suspension and wheel width differences are only a quite modest part of the reasons.
MOST ALL modern tires are capable of out-handling the bike and MOST RIDERS. They stick to
the road rather well, even at big lean angles under fairly severe conditions at speed. That's the truth.
BUT, there is another truth: the FEEL can make the rider THINK the bike is handling Wonderfully...OR...poorly.
When reading tire comments/reviews, FEEL is NOT well differentiated.
MANY modern tires have profiles, type of rubber, type of design, type of tread, ETC., that give a "quicker
handling" feeling. Many modern tires FEEL to the rider, particularly when starting out on a new set of
tires they have not ridden on before....that they are considerably OVER-inflated, and might be called
SKITTERY, and 'quicker handling' is often the term used by those riders. Many a rider is somewhat
timid, particularly on wet roads...but, the tires may feel ...or be described...as quick, or twitchy, or skittery,
etc... on dry roads too, even after thousands of miles on the same tires. Wet roads tend to create a
considerable apprehension for many riders. Many riders did not experience wet roads much when
learning to ride, and are slightly to moderately freaked-out by the idea of riding in rainy conditions.
They have hardly ever, maybe some never, ridden on quite wet roads. These types of riders may
especially freak-out on gravel or dirt roads...even at just the thought of being on gravel roads. I KNOW
riders who are NOT going to attend a function, such as a TechDay, etc., if the driveway is gravel, or too
steep, etc. This is not an article about how to ride bikes, I am just telling the truth about various riders.
If a rider is ACTUALLY timid (hard to find out!), how much weight will you give to this rider's opinions
about tires? MAYBE YOU SHOULD pay attention...you might be like him/her!! The truth is that most
motorcyclists are NOT after racing experiences! Many do NOT want to ride aggressively. MANY are
OLDER and don't like 'taking chances' (which words have variable meanings to riders). Many riders
are simply out for a "Gentleman's ride on Sundays"; or a mild ride to a TechDay or camp-out. WE NEED
to consider that rider too, in talking about tires. That means I NEED TO, also, in reporting on tires.
I try to analyze tire performance for ALL USERS. The exception is real RACING, where skills are likely
quite high, aggressiveness is a given, special tires are in use, as are special techniques...such as
pre-warming the tires in the pits, wearing sidewalls rapidly, speeds are high...& quite a few other things.
8. Mileage one gets from tires depends on speed, loading, tire pressure, road condition, style, etc. Be
very cautious about who you listen-to. You may want to ask very detailed questions!
9. Riders want information on tire brands, models, & characteristics; and for conditions they may never encounter!
This is very much like doing discussions over a few beers or around the campfire, or 'garage racing'.
In MANY instances, Rider's viewpoints on their own tires are NOT substantiated by real testing. I hope to
provide REAL information in this article.
10. I have tested tires on both asphalt roads (especially with various types of tar repair stripes, which also
tests suspension stiction); concrete paved roads as well as gravel/hard-pack; and, occasionally rather
soft stuff (yes, on road tires). My testing was, perhaps, unusual. I did REAL ACTUAL CONTROLLED
TESTING. I have racing experience both on and off road, on 2-wheelers and sidecars. I have available
close-by my home some very specific roads that I have CONSISTENTLY used since 1973 for testing.
These offer a wide variety of surfaces & conditions. I tested in below freezing temperatures, as well as
hot Summers. I made a point of trying to ride when it rains, because it does not rain a lot here. I even
tested on somewhat icy roads (!!). When I first moved here I had a R75/5 for good weather/roads....but
I also had a "light weight" (for back then!) dirt bike, shod with knobbies, that I rode in the snow. It was
great fun but physically a lot of exertion. I no longer do that in the snow (although I still do ride my sidecar
rig in the snow....lots of fun!).
11. "Classic BMW Airhead Handling" is GENERALLY & LIKELY AVAILABLE ONLY with the original type of
tires in original sizes. This is particularly so with the older models that came with 3.25 x 19 front tires &
4.00 x 18 rear tires. Tires that have the classical ribbed front & matching rear, with exactly correct sidewall
stiffness, ETC....that will probably duplicate the 'original ride'; are such as the Continental's RB2 front &
K112 rear tires. Some Metzelers have such handling. In order for a close-to-full classical experience ride
use the same types of tires that were designed to work together as a set. It is possible that some
ChengShin tires will also exhibit the classic feel. Bridgestone has the Accolade tires, front is ribbed,
but I do not have any experience with them. One of the problems with trying various classic/heritage
(or similar) tires is that MOST riders no longer have the exact same type of original shock absorbers
and springs; or, those are not in good condition; or, other parts of the motorcycle have aged; or,
have made other changes. Just changing the type or style of handlebars WILL AFFECT the bike feel.
BUT, if your bike is in reasonably decent condition and reasonably close to original specifications, you
might really want to try a set of the old tires (which might well have changes in them, so you might
NEVER REALLY get the SAME EXACT feel as when the bike was brand-new). It REALLY IS worth
trying these tires, if you want to experience something closer to original feel. If you don't like the tires,
sell them to someone else. I think you will enjoy being a 'sporty fast-gentleman-rider', however.
Up until maybe 8 or 10 years ago, some tire sizes were getting harder to find in proper INCH sizes. While a
number of the old sizes, such as 3.25-19 are available from several manufacturer's, some are...or were...
not very common. An particular example is the 3.25-18 used on the R45 and R65.
HINT: Try: http://www.durotire.com/ ........and click on CLASSIC (or similar word). BUT, do, FIRST, check
into the Heritage line of tires from Metzeler, and the Continental classic tires, and the Bridgestone Accolade.
Many riders no longer use the classic inch sizes. NOW-A-Days, MANY inch-size tires are available; various
brands/models. MANY are using metric-sizes. But, many are now trying the newer inch-sized tires too.
Several manufacturers now have tires specifically made & advertised for "Classic Bikes". These tires are
really worthwhile looking into. This advice INcludes the new radial tires designed for our classic bikes.
All these things, including suspension changes, pressure changes, etc., lead to a QUITE DIFFERENT ride
(from original stock configuration). Most riders just want a good ride with good handling & good tire longevity
& don't really care about the 'classic' feel & handling. MANY have a lot of experience on other brands and
models of bikes, & may want their Airhead to FEEL & HANDLE similarly, or 'just better', whatever THAT
MEANS TO THEM. LOTS OF VARIABLES.
It is DIFFICULT TO TEST TIRES WITH SO MANY IDEAS, SO MANY TYPES OF RIDERS, SO MANY TYPES
AND STYLES OF TIRES. Think seriously about yourself, your abilities, your actual riding, TRY to KNOW what
you like & want, and if you don't know, well, nothing says you cannot try a few different tires.
12. MOST 'modern' tires on the OLDEST Airheads (perhaps to as late as 1985) require considerably higher
pressures than stated on the tag under the seat or in the owner's manual or in some tire manufacturer's
literature. BMW did better by the late eighties onward...regarding tire pressure recommendations. Failure to
inflate to proper higher values will result in poor handling; the bike may feel like the tires are trying to roll off
the rim, etc. When you DO inflate to a higher value, the tire MIGHT feel skittery, until you are used to the
improved handling. THE TIRE PRESSURE LISTED ON A TIRE SIDEWALL IS NOT THE RECOMMENDED
TIRE PRESSURE. IT IS A MAXIMUM TIRE PRESSURE, BASED ON WHATEVER STANDARDS THE
MANUFACTURER USES FOR THE CARCASS, ETC. CONSTRUCTION & pressures versus industry
classifications. I treat tire pressures a bit more in-depth in http://bmwmotorcycletech.info/TireRepair.htm
in a section near the bottom of that article. FOR YEARS I have been telling people that the tire pressures
printed in your owners booklet, & in various literature, and & particularly so for BMW's prior-to-1985
models (after which tire pressure recommendations are a more reasonable but not perfect, in MY opinion),
are MUCH TOO LOW....for modern tires.
Here is a link to a page with charts of recommended tire pressures. I ran across this information in
November, 2014. I mostly agree with the page. YOUR tire size may not be listed, probably isn't, but you
can interpolate & assess/guess. This is one of the very few tire pressure guidelines that is generic;
and does not have lawyers telling the tire makers to recommend only what BMW says in BMW
literature WHICH PROBABLY IS INCORRECT FOR THEIR TIRES!!! I wish Avonmoto had published
for many more sizes. You might notice, even with a quick glance, that the guidelines don't have
anything much or overly-specific to say about TYPES of tires. That's because differences, unless
for specialized purposes, are NOT ALL THAT PERTINENT. You may notice that tire pressures
are recommended that might be higher than in other tire makers literature, particularly if they use
BRAND names for bikes. That's another way of saying that lawyers have too much influence!
13. When the rear tire 'squares-off'; some do this rather faster than others (dual-compound tires are better at
not squaring off fast), handling can be poor in curves, particularly fast changing twisties. INstability (wobbles)
can be very apparent with a squared rear tire, if such problems happen.
Some types of instabilities can be HIGHLY dangerous & not just annoying. In some
instances, when combined with, perhaps, an improperly adjusted steering head
preload; & maybe, OR NOT, other things, such as saddlebags, backrest,
windscreen...etc..........you can SUDDENLY get a very bad wobble, at high speeds.
YES, I did just say that squared-off REAR tires can cause problems!
That has been extensively PROVEN, and you need not take my word for this.
|A bit about me, my testing, etc.....
Penny hates two-up riding, & since I was hardly riding two-wheels on the street anymore; in January 2014, I disposed of the last of my 2-wheelers. In the garage at the time was an 84 R100RT, an HP2, and the K1100LT-EML-EZS conversion. Testing on 2-wheelers did not totally stop, & was sometimes done now & then on borrowed bikes, old friends' & old customers' bikes. I began to miss that RT more & more; even though I had not put many miles on it the several years before I sold it (or, more accurately said, before the new owner finally picked it up, as he had bought it a long time previously, just kept it here, I was allowed to ride it....and maintain it too, of course).
By Spring of 2015 the lack of a 2-wheeler (especially one that was MINE) was really bugging me. I was also beginning to be UNhappy with showing up at various events, TechDays, etc., just on my sidecar rig. I purchased another R100RT, this time a Monoshock 1995. It was/is my intention to make sure its suspension is in excellent STOCK condition, & to, again, do testing on tires that I have previously had NO experience with... or very little experience. BUT, by late 2015 it was becoming apparent that while I was capable of such serious testing, I no longer really wanted-to-be-so-aggressive. I had other interests, such as helping the children in my community by being a very active Member of the Kiwanis of Tahoe Sierra, and Penny and I were active in the community in other ways. BUT, I realized, after getting back into 2-wheeler riding on the on the street, that I really DID want to do some occasional aggressive riding, but only in short spurts. I tired more easily, I had less stamina, was weaker from the slow part of aging that reduces one's muscles.
I have been blessed in my old age with good reflexes & eyesight. I live in an area that has a variety of terrain, including all sorts of types of twisties in mountain passes. There are some deep sand areas (these "Sand Pits" were actually set aside for motorcycles only), 3 miles from my home. My paved-road testing area gets mixed weather conditions; has various pavement styles & conditions & more than one type of tire snake compounds. A few years ago, the State of Nevada did some paving repairs near here, where they 'tested' a new type of tar snake compound. It was a disaster, and they had to remove it! I did a lot of testing on that 11 miles or so of road before the repairs using the new compound, then did some testing on that awful stuff; then, afterwards, when the State removed the new-fangled plastic compound, and replaced it with real tar. Very informative!
Some areas near here that I use are fairly flat & smooth with excellent pavement. One area has very ugly curvy (poor workmanship!) rain grooves & this same road has some broken and uneven pavement sections. I also have a freeway 26 miles distant (with & without rain grooves). There is a road I do very high speed testing on (in conjunction with my association with a bike magazine; no, you will not be told who/where). I also have two dirt areas, one is medium hard-pack; one is very soft & deep sand/gravel (that one is, as noted, only 3 miles from my home). If I get on a racetrack with a bike, I will note the types of tires, and how they feel/handle, pressures, etc. Since my wife hates seeing me on a track; she does not want me on 2-wheels at all... besides our bicycles! I have made some compromises. I have consciously cooled-down my most aggressive testing. I am not as strong as I used to be, age has caught up with me, & I won't heal fast if I drop a bike. SO FAR, I have NEVER, EVER, dropped a bike in my many hundreds of thousands of street miles. I may be just lucky. I am, more & more, depending on tire reports from a few friends, who may be as anal as I once was; or at least agree with my style of testing & can do true analysis. I am, however, still testing tires, less aggressively, but with vastly fewer miles per type of tire.
>>>ONCE IN A WHILE I will specifically test a bike that has a squared-off rear tire, doing this for stability testing of the entire bike besides tire feel. Same for suspension, stiction problems, etc. I also try to test bikes, when I can, that have large windscreens or fairings, perhaps with tour bags and a backrest.... to see how they handle at various speeds and direction changes. In other words, I may combine bike and equipment testing with tire testing!!
For NEW tires, as always, my habit was/is to run the tires in reasonably for 50 to 100 miles, slowly increasing aggressiveness over those miles. I make notes, play with tire air pressures (I take along a small electric compressor & I use a very accurate Bourdon type gauge)....and when I find hot/warm pressures that work well, I recheck with the tires cool, so I know what the normal tire pressure should be (tire pressures for normal use are checked with the tires cool, that is, not ridden yet).
MUCH of what I hear and read about tires seems to be based on nothing but thin air, or ...the owner has purchased them and WISHES they tested as he says they do. The rider may also have NO IDEA of what he is talking about. I realize this is cynical, but it is the truth. I am WELL-AWARE that few do REAL tire testing, .....but many have UNsubstantiated OPINIONS.
Tires by brand, model, and description of performance:
(1) A TUBELESS tire that does NOT use steel strands in the tread is much more likely to have a LASTING
on-road repair, by using sticky strings or internal patch. This is particularly so if you are using such as
the Stop'nGo mushroom type of plugs, which, otherwise, require a lot of reaming on tread area puncture
holes on steel ply tires. The Avon Roadriders, as ONE example, do NOT have steel plies. Conversely,
that makes them POSSIBLY more conducive to punctures. All this is strictly speculation! I am not knocking
Stop'nGo, I carry their plugger kit with me! I MAY run some puncture tests on tires!
(2) If using metric tires, use the 90-90 or 100-90 front if using 19 inch. Pre-1977 bikes need a wider fender
mount for the wider 100-90 tire, 46-61-1-234-907, this is common to all brands for that size. I strongly
suggest that if using metric sizes on you early TWIN-SHOCK Airhead, that you use 110/90-18 rear, and
NOT a 120/90-18 rear...it is not generally recommended by me for twin rear shocks Airheads models,
specially the rear drum brake models with cast wheels (Snowflake).
This is the first new style report of what I hope to do in the future: that is, highly detailed
I had, in the past, very limited mileage on the AM26. I was then not fond of them in
moderate to deep rain; nor on paint stripes, & did not particularly like the AM20/AM21 either.
Avon Roadriders (AM26) are moderately priced; DO, reportedly, seem to get good mileage,
but some few have reported the opposite. Roadrider tires have have been reported with
cracking. Many, if not most, don't replace them for cracking. There are no reports of actual
tire failure problems (AFAIK!).
Since I reported the above, I have had the opportunity to put the AM26 tires through
considerable additional testing. Fortuitously because my 'new-to-me' (1995 R100RT) bike
came with them, with low mileage on the tires. This motorcycle is a MONOSHOCK,
specifying a wider tire than on early Airheads, on the rear. This motorcycle specifications
are for METRIC sized tires, tubeless-rated and so used as tubeless. The wheels on this
motorcycle were stock, as was the suspension. Standard equippment, with a few notable
exceptions: The BMW rear trunk that came with the motorcycle was NOT fitted. A
fairly tall backrest is fitted. The stock stock windshield had been replaced by a
Parabellum, this type has a curved bottom design that allows air to flow at the bottom);
I cut the windshield to ~13 inches in height. That height is not optimum for weather and
buffeting, but allows me the view, and slightly sporty downward forward position I prefer,
yes, even on an RT, and even for my age.
Avon makes these tires in directional & bi-directional (Universal). The tires I did this testing on
were a 100/90-18 front bi-directional tire (stock size for the bike is 90/90-18), with the proper
tire direction for the front, as marked on the carcass. Rear was stock 120/90-18, single direction
marked. Rider weight 150. Shortened windshield (15"). Tour bags (empty), Tour Rest, NO rear
trunk fitted. 1/4th to 3/4 filled fuel tank. Tires were 4 years old FRONT; and 3-1/2 years old REAR.
Neither had any visible cracking nor other deterioration. Rear tread still rounded. Tires had
~5000 miles for the initial testing. It was fairly warm for the tests (70's-80's F.) and tests were
on both smooth and slightly broken and cracked concrete & asphalt. I purposely did some freeway
riding at low speeds and up to 90 mph, specifically hunting-for, and using, rain grooves, at various
speeds. I tested those grooves with my weight forward, as well as very considerably rearwards.
At first they felt especially twitchy to me, same...or more so... as previous tests. I have chalked
up SOME of this due to the oversize front tire, which causes the bike to have a somewhat extra
tendency to 'fall into turns'. This time I did pressure change testing, & noticed the twitchiness
no matter the pressures used. That never completely disappeared. It took a while to get used to.
Direction changes happen quickly with low input from the rider. Handling over-all is light. Braking
is good. These tires FEEL like not enough rubber is touching the road. They feel like almost any
reasonable pressure I tried was too high, but they STICK WELL...except they are rather slippery on
such as paint stripes. While this is so for all tires, these were a bit worse.
Because of these things, I do NOT recommend using an oversize front tire, plus, due consideration
should be given if you ride a LOT on grooved roads.
These ties DO moderately track rain grooves; but NOT NEARLY as bad as straight ribbed front tires
do. Some serious testing, perhaps my last time at doing such highly aggressive testing, was done
going both up & down a particular twisty mountain pass that was rather steep, but smooth, as the
asphalt was recently paved, within a couple of months. Quite a few runs were made to determine
the best tire pressures, which were corrected to cold values. I repeated the final test on a later cool
morning, setting the cool tire pressure to 32F, 36R; the factory recommended pressure.
>>> OVER-ALL, A SURPRISE!! These 1995 BMW factory recommended pressures worked well!!....for a
good compromise of handling & comfort (BEST performance, pushing the tires rather hard, note my
light weight, was at ~34 front and ~39 rear). For a heavy rider and/or heavy loads, especially for
touring at high speeds, I suggest 34-36 F & 40-42 R. Over-all, these tires work OK under all conditions
so-far tested, subject to my comments. I think if you need to fix a flat, that standard soft plugs as
provided by Stop'nGo, for use in their special gun, would work well, and so would sticky strings,
because there are no steel strands to cut the plug or string ....see earlier in this article.
The following caveats:
NO mileage tests ...may be late 2016 before I report on that.
Seem fine on normal lightly wet roads, not yet tested in deeper water.
Slippery on paint stripes, and BADLY so if the road is wet. SAME FOR SOME TAR SNAKES.
Have not yet tested the tires on deeper gravel & dirt roads. Were OK on hard pack with
shallow gravel top surface.
Rain grooves: I fully tested these tires on rain grooves on several roads, including high-
speed freeways, & on two separate occasions, on different roads. They do follow
rain grooves, especially so if the grooves are pronounced and not straight, but it is
mild to moderate, & probably will not overly annoy anyone.
Bottom line: good tire, but I think I prefer the Michelin Pilot Activ over these; but need more testing
on the Michelin; and I haven't any experience on the new Continental Classic Attack's... yet. I DO think
the Avon Roadrider's are worth the cost, which is somewhat LOWER than the Pilot Activ, etc.
For years, as noted below, the Bridgestone S-11 (Spitfire) tires were ones I used for comparisons.
I think they FEEL considerably more stable than the Avon RoadRider; even on rain grooves. The Roadrider
REAR seems to have rather little squaring-off, at least at ~5000 miles. I will have more to say on that in the future.
I still like the S-11, and perhaps prefer them for a high percentage of street riders.... all things considered.
Dual-sport riders: the Avon Gripster AM24 has been around for a LONG TIME and it is a WELL-
proven tire, it is a fairly good street tire, if a bit noisy, sticks WELL in cornering, quite stable &
not bad in rain either. Works pretty good in off-road gravel & hard pack, fair/poor in mud, &
are, perhaps, a bit rough/hard feeling. I suggest using about 31 psi front and 35 psi rear for all-around use.
These are possibly not quite as good as the Michelin Anakee for street and dirt.
The Continental TKC 80 is better than the AM24 off-road.
Avon's Distanzia AM43/AM44 tire is much more of a street tire, decent in the rain, only
fair off-road, but fine for the street rider who ventures off the road on occasions.
This is the Avon Distanzia (front)
NEITHER of these Avon tires would be my choice for a bit deeper or rougher
off-road dual-sport work. Both the Gripster & Distanzia are primarily paved road tires,
with modest to OK off-road capability, the Distanzia having the edge for the street & life,
at maybe 1/3rd more cost. The Gripster is a quite decent tire for the person who is primarily a
paved-road-rider, yet ventures off the road now and then, who may even be a bit
aggressive off-road. This AM24 is a darn-good all-around tire, and works well in
anything but mud (keep in mind that usually only VERY aggressive tires work in mud).
Bridgestone: S-11 Spitfires (tested: 110 rear, both 90 and 100 front).
ONE of my old favorite ROAD tires, all things considered. They are truly GOOD for the $.
I first tried these MANY years ago on a SWB R75/5, & liked them immediately.
Very predictable handling in all conditions, although like any true road tire, they are NOT for
deeper soft stuff or mud. Decent mileage & good grip on pavement. Dual-tread-compound
construction is part of how they get the performance (esp. mileage). Use the 90-90 or
100-90 front if using 19 inch (pre-1977 bikes need a wider fender mount for the wider 100-90
tire, 46-61-1-234-907, this is common to all brands for that size). Use 110/90-18 rear.
There is also a 120/90-18 rear (not recommended by me for twin shock models,
especially the rear drum brake twin rear shock models). S-11 tires are also available
in sizes to fit the much later Airheads and also K bikes. Highly recommended
by me for many years now. Even though a somewhat old design, they offer REALLY GOOD
over-all mileage and performance, especially for the $.
I really like these tires on Airheads and K bikes. NOT available in all sizes (you should check,
but 17" were not available last time I checked).
>>>>Because of my VERY extensive experience with these, I tend to use them for comparisons.<<<<
My 1984 R100RT got 10,600 miles on the last REAR S-11 tire. The bike was mostly driven at
maximum legal highway speeds (and somewhat higher). The tire still showed tread that was
usable, but it was down to almost 1/16". A good tire for all paved roads, decent in rain, & even
quite OK for those that ride moderately aggressively. Cheaper than many other tires. For
those that do mostly highway riding, with occasional rides on gravel and hard pack, the S-11
tires are quite good because these dual-compound rear tires do not tend to flat-square quickly,
although, like all tires, it will, eventually. Squared-off rear tires can lead to high speed weaving
and other instabilities, even dangerous types. Again, note that this happens with ALL rear tires,
but these tires DID NOT exhibit it very much. This alone makes their value quite good,
considering the mileage capability, a relative bargain....AND, they handle WELL, and PREDICABLY!
NOTE: The Michelin Pilot Activ, available in INCH sizes, may be competitive (or more!)
to the S-11 and maybe the BT45 for performance, if not price. I may have more to say
about the Pilot Activ later....so see below for Michelin.
BT-45: Another Bridgestone dual-compound tire. Probably a bit better than the above
S-11 in WET conditions, maybe in all conditions, but at a large $ increase. I do NOT
think them worth the substantial extra cost. HOWEVER, you might. Perform well, under
all paved road conditions. A bit better off-road, than the S-11. They do not feel the same
as the S-11, probably due to the tread design & possibly an internal carcass change (?).
Bridgestone Accolade tires, front is ribbed: I do not have any experience with them. Supposedly
these can produce a more classic, original/early BMW ride.
Cheng Shin: Chinese-made, the brand used to have a bad reputation for problems. That is NOT
SO now. These are good tires delivering OK performance, at a low price.
The 906 model is quite similar to the Metzeler Laser ME33, and it matches well with the
907. Decent tire in both wet and dry. I have not tested many Cheng Shin tires.
Continental: Old TK 16, TK17, NOT recommended. Especially 120 size, which is much too wide
for ANY dual-shock airhead. Listed here only for those comments. Obsolete tire.
Continental TKH23 front and RKH24 rear are long life tires, available in 3.25H-19 front
and 120/90H-18 rear. I cannot remember if that rear can be fit, it might have the too-wide
fit problem as the TK17. BUT, they make this tire in a 4.00-18 rear...and it DOES fit.
Otherwise, decent tires, reasonably priced.
TKC70: More paved-road than off-road. Probably similar to the Metzeler Tourance, over-all.
If your riding is more off-road than paved, try the TKC80. I have personally not ridden on
TKC 80: Is truly for dual-sport use & good on pavement (not so nice, but OK/Fair when the road
is wet). I like them even in rather aggressive riding, although feels a bit squirrely to me
(even considering the tread). Limited sizes available.
This tire grips OK on pavement, on sand & gravel, dirt, even reasonable on mud!!! It is a GOOD
choice for those going off-road more often....yet retains good performance on the street,
FAIR when wet, even "OK" on snow. One of my favorite all-around dual-sport tires. It
corners good. Does not last as long as the Metzeler Tourance's.
It is fairly quiet, inspires confidence in how it FEELS. A really good tire. I think
MOST riders, no matter the model of BMW, will like this tire, even if you are a street rider
(but you do maybe half your riding truly off-road). If you want all-around performance in a tire that
will be 'capable of any surface', even a bit of mud, this IS THE ONE. Original equipment
on some BMW models.
Drawbacks: Expensive. Tread too aggressive for "mostly" street riding.
If you like the TKC80, you might also want to try the TrailAttack. You also may want
to look at what I say about the Kenda K784. I have NO experience on the TrailAttack, and
RB2/K112 (also TK22): Original types used on the OLDEST Airheads as ORIGINAL equipment.
I have not ridden on any in many years; I always disliked the way they followed rain
grooves...but they do...or at least did....offer the classic BMW soft ride, last pretty good used
with original 'high-speeds, two-up' tire pressure settings. I might try testing some of the new
modern versions as I have heard the rubber compound is improved since Continental re-started
production some time ago on these. I won't use my own bike.
Owners of early airheads that came with the 3.25-19 front and 4.00-18 rear tires, as stock sizes, should
try a set of these Continental tires if they want the classic ride AND LOOK. You won't get that classic ride
if you have a modified suspension.
Note: I don't purchase Continental tires myself due to how they treated my shop when
Continental had a bad batch of tires, many decades ago. But, I do NOT, in the slightest, want to
discourage YOU from trying these tires, as you may love them. If you intend to ride on classic
tires, I also suggest the Metzeler tires like the ME11, etc. Accolade tires??
BMW installed Metzelers in the old models/sizes, besides Continental's.
This is the Continental RB2 (front)
Classic Attack Radial (Conti Attack Classic Radial): This is a new type tire from
Continental. Continental says that they specifically designed this tire, A RADIAL 0° type,
to enhance & sharpen the handling of older classic bikes which were originally
designed for bias-ply tires. I have not yet tested these tires. From a look at the tread
pattern, I think the tires MIGHT NOT track rain grooves, & should feel FINE. The tire is
supposedly fairly high mileage with excellent grip & fast break-in.
The tire is available only in metric sizes (??). In the metric sizes, the 100/90R19 57V TL, a
front tire, is expensive, although discounts may be available. That tire, like all of that size,
will probably not fit earliest Airheads without the proper later fender brace, 46-61-1-234-
907 from the 1977-1980 /7 series. Probably will need the later fender too.
The other two usable metric sizes are 110/90R18 61V TL and 120/90R18 5 65V TL, these
two are designed for rear use. I suggest not trying to use the 120 size on anything but a
RS or RT that has the 2.75 rear rim, although you might be able to use the models with
2.50 rear rim. The 110 is likely the BETTER choice. NOTE the load rating
on these tires, compare to your previous and other tires. Note also the "TL". These
tires are V rated; if used with tubes, you should reduce the speed rating by one step.
That's FINE for Airheads, who hardly usually need more than an H rating, let alone an S or
V. Some riders who have tried these LOVE THEM. As noted, no personal testing
information yet. Tom Cutter reported that these type tires were easy to R/R, provided a
comfortable ride, were stable, and had a nice feeling.
... somewhat expensive. Other sizes may become available.
I am looking forward to comparing these tires to Michelin Pilot Active and Avon RoadRider.
Dunlop: Vintage K70 front, 3.25H-19; K70 rear, 4.00H18/.
Somewhat similar in some respects: Dunlop F11 front 100/90H-19; use it with a K627 rear
110-90H-18. Reasonably OK, obsolete now.
K491-Elite II: This was a Premium-cost tire, premium priced and a VERY long lasting VERY high
mileage tire. Pretty fair wet handling too for such a long lasting tire, and good on rain
grooves and reasonable IN RAIN. Use 90-19 front (some can use 100-90) and 110/90-18
rear. The oversize 120/90 rear should also fit the early eighties Airheads. Tire has
probably been discontinued. It was a classic high mileage tire when available. Some
loved them for LD touring on both lighter and heavier bikes. My tests agreed.
TrailMax Dual-Sport: can't recommend these; pretty lousy off-road.
D606: This is a good mixed use tire, for tarmac AND off-road. It is priced in the lower
area, and is good on road and off-road....with an emphasis for off-road. My limited
testing found some high speed instability, but I did not have time to test pressure
changes nor loading in that regard.
Good performance for the cost. I think the Michelin T63 is better.
GOOD TIRE...and you MIGHT like it over the Conti TKC80.
Heindenau: The K60 Scout tire is nearly as aggressive as the Continental TKC80, but costs
a LOT less. You may really like them, over-all. LIMITED experience.
Kenda: K784 Big Block. So-so on pavement, pretty damned good off-road, even quite good
in mud. Wears relatively fast...to be expected for good off-road and even mud type tire.
Maxxis: C6011 is good, not sure if it is available in the 18 inch now. See Cheng Shin comments.
Metzeler: (see Continental, RB2/K112, for comments regarding the Metzeler ME11)
***UPDATE, November 2015: Metzeler has moved some of its existing tires, and some new
versions of old types, into a new category, called the Heritage series. While
this includes the Lasertec, it also includes some classic Metzeler tires, mostly
updated with newer compounds and manufacturing. This should bring better
handling and longer life, but I have NO testing experience on them. The tires
will mostly have the original tread profiles and appearances. These tires are
the Perfect ME11 front, Perfect ME77, Block C.
ME33 Laser: both standard & the low profile metric. I recommend the 3.25 or 3.50
front. If you have gone to an oversize rear, use the oversize front. This tire will SEEM to follow
some types of rain grooves, but NOT as badly as a ribbed front tire. You can use this
front tire with many other rear types. Decent in the rain, good dry grip (LIKELY WAY beyond your
bike's capabilities). For mileage, you can expect decent, if not outstanding values. Some tendency,
sometimes, to cupping. The ME33 tread design was unique when introduced, and has
been copied by others. It has a lighter faster turning 'feel', and almost always can be used
with just about any rear tire design. There was a K compound version that was, well,
good enough to race on! Both NLA, I think.
Lasertec: I do not like this tire ...for the less-aggressive rider. It is twitchy, gives an unstable
feeling. Aggressive riders might want to try it. This tire does NOT feel like the ME33 Laser to me.
They tend to follow rain grooves....likely due to its single circumference groove (or multiple wiggle type)
groove(s) in the center of the tire. If you don't have grooved highways, or don't mind the (not awful)
instability, then you MIGHT like this tire. I was surprised by the twitchiness, & while
different, I compared its twitchy feeling to the Avon RoadRider. The twitchiness may be
partly "less-rubber-on-the-road" FEELING. I did NOT do tire pressure testing. NOTE that
a lot of the more modern tires have some very light handling qualities, which I call
twichiness. THUS, you may well want to try this tire. It DOES stick well, corners
nicely, and gives some confidence in tight twisties. This tire should match up with many
of Metzeler's other model type of tires.
ME55: An old favorite for some, was also available in 120 size for the rear. I never liked
this tire, although it gave a good compromise on handling and mileage.
ME88: Front & rear versions. A mileage tire, reasonably good handling; one of my
old favorites for use front & rear for TOURING. Interestingly, this tire also worked well
as a rear with ME 33 Laser front, for more aggressive paved road riders. I have tested
ONLY those made in Germany. Discontinued...booo hooo.
ME880: NO personal tests yet; no trustworthy reports yet either.
Tourance: OK on the street, "fair" on gravel and hard-pack dirt. The Michelin
Anakee is probably better all-around, by a bit, wet and dry, for dual-sport. The Continental
TKC70 is roughly the same, performance-wise, as the Tourance. Tourances are NOT good
in any sort of mud.
Enduro tires: Metzeler has a selection of these tube type tires to fit older airheads.
Enduro 3 (Sahara or Sahara 3) is a good one for mixed on-off road. It is premium
priced, however. Watch the WIDTH....Enduro tires may be MUCH wider than their size
might lead you to believe, and thus may not fit on twin-shock models, due to swing arm clearance
problems. Nearly every motorcycle tire manufacturer has its own enduro tires.
Metzeler MCE Karoo: These are good GS type tires for off-road, fairly decent on
pavement. I suggest you don't mix other types on the same bike. For pavement
use, especially if the weather is cold, let them warm up before getting aggressive with
them. Many equate these tires with the Continental TKC80, I think them only
somewhat similar. There is now a Karoo 3...no information nor testing by me, yet.
Macadam 50 & 50e. 100/90-19 & 3.25-19 front; 110/90 & 120/90 & 4.00 all in 18 inch rear.
Some really liked these. I don't have enough miles on them to say much.
The Pilot Activ replaces the Macadam. The Pilot Activ SEEMS, in LIMITED testing by me,
to be better for wet streets, handles better, reports say long life; may be
comparable to the Bridgestone BT45, per SOME. In 2013 I installed a rear Pilot Activ 4.00H18
on the REAR of my R100RT, and only did mild testing. The front was still a 3/4 worn
Bridgestone S-11. I intended to later install a front 3.25 H19 Pilot Activ, & do testing all
over again. The REAR Pilot Activ worked nicely with the very different
tread profile on the worn front Bridgestone, and with different pressures too.
Previous tests on someone else's bike, with BOTH tires being Pilot Activ's, were not
extensive enough for me to say much more until Summer of 2015. BTW.. I had a miserable
time trying to mount the Pilot Activ 4.00H18 to the 84 R100RT rear snowflake wheel.
One side went to the rim bead area OK, the other VERY difficult. Because of this, I modified
my air equipment AGAIN, and then it went on OK. I added that new inflation information to my
http://bmwmotorcycletech.info/tirerepair.htm article. This tire is very stiff in the sidewalls,
even the tread. Do not be discouraged by these remarks. This tire has a very well-made
bead edge, which should offer better sealing on a tubeless rim than others...but a tubeless
rim and a tube type rim do NOT have the same shape for the bead area...the angle is 9°
different, for instance, in some cases. For those who use a tube type rim as tubeless,
I think this tire will do better than many others in the instance of an air leak or flat.
This is speculation on my part. Such usage is not recommended by many. There IS an article
on this website, about such usage. http://bmwmotorcycletech.info/section6.htm
***NOTE: I used standard Michelin Butyl tire tubes for my testing.
NOTE: In the summer of 2015 I had the opportunity to test ride a WELL-MAINTAINED RS
that had these tires on them, with less than 2000 miles on them. I liked the handling!
Anakee3: The Anakee 3 is different from the Anakee 2. The 3 is for mixed on and off
road, seems pretty good all-around until you get into mud, where it's poor. Emphasis
is on pavement riding. EXPENSIVE. May be difficult to mount? Competition for these
tires are the Continental Trail Attack, the Avon Distanzia, and Metzeler's Tourance.
T-63: For more aggressive off-road riders, handle decently on dry pavement (not
too bad on wet roads either); probably one of the best buys for mixed use (dual-
sport, with a fair amount of emphasis towards off-road). The T63 is a truly good tire.
((Remarks: A friend told me about this tire, and how he, on a bike loaded with luggage and his
girlfriend on the rear of the seat, practically melted the tire from very high speeds,
in Arizona, in exceptionally hot weather. I went out of my way to test this tire on someone's
It is less expensive than much of its competition. This tire has a moderately
aggressive enduro tread, so unless you do some off-roading, don't get it. This is NOT the
tire for quite heavy loads at quite high speeds, coupled with very hot asphalt (see remarks!).
NOTE: I have ridden ~ 78 miles on an Airhead equipped with these, but someone
I trust has also reported to me about them, who has a LOT of miles on them, some in
very hot weather, on tarmac, with a passenger & luggage...and we have the same opinion.
>>>While the tread looks pretty aggressive, the tire is somewhat milder than it looks.
I do not know about mileage life, but I think the tire worth the modest cost.
Pilot Road 2: Seem to be excellent on Classic K-bikes...very limited experience here.
Pirelli: Scorpion: Not recommended for GS. I have NO miles on them. Some reports
say they exhibit wobbling if mixed with other tires, but I have no definitive information.
Sport Demon: reportedly will change handling for the worse AFTER some miles
are on them. NO personal experience.
Shinko: NO PERSONAL aggressive testing yet. One report from someone whose riding skills are
very good, and can ride hard enough to test tires reasonably well, likes these, &
compares them to vastly more expensive tires.
The "everything else" section of this long article:
1. Some folks have trouble understanding tires sizes. On metric tires the first number is the width in mm on a
nominal width rim, the second number is the aspect ratio of the sidewall to tire height. Metric sizes and inch
sizes are not exact equivalents. GENERALLY speaking a 3.25 inch size as originally specified can be
substituted by a 90 metric (often coded as MJ); a 3.50" by a 100 metric (MM); a 3.75 or 4.00 by a 110
metric (MN or MP); and a 4.25 or 4.50 by a 120 (or MR).
There WILL BE handling differences if you do not use the originally specified size of tires. Those that have
heavy loads ...may want ONE size oversize tires. It may behoove you to look into the load carrying capability
of your proposed new tires...usually molded/printed on the sidewall. SOMEtimes a larger tire is rated for a
LOWER load. Using a stock rear tire, let us say 4.00-18, with a substantially oversize front tire, is not the
best combination, as the bike will PROBABLY have a tendency to fall into turns a bit; but I have NOT found
that too excessive if not going too big. As I noted; sometimes an oversize tire will have LESS load
capacity, and you MAY have to look at the manufacturer's technical data to find this out.
***SOMEtimes an oversize tire will have LESS contact patch on the ground....due to the round profile!
Do NOT willy-nilly increase tire sizes! This is particularly so for the front.
IN GENERAL: OK for a 3.25 front to be 3.50 or 90/90 or 100/90; and, OK for a 4.00 rear to be 110 or
120. There is a 4.10 size that MIGHT work, but I have NO DATA, NO EXPERIENCE. I also have very
limited information on using 80 profile tires....Aspect ratios of 80% will NOT always work on early Airheads.
It is often a matter of the sidewall characteristics not just other fitment problems. Most of the early
Airheads came with inch size tires: 3.25 x 19 inch front tire and 4.00 x 18 inch rear tire. For some time
FEW tires were made in those sizes, but availability has improved. In general, these old sizes were in
what, today, is called a 90 profile. Some were closer to an 80 series. NOTE that the old Airheads
(except G/S) did not come with enduro tires, and I mention this because most enduro tires in 4.00 x 18
will be VASTLY wider than a 4.00 x 18 paved road type of tire. An enduro tire may well NOT fit on twin
shock Airheads, not enough room between tire and driveshaft housing. This is particularly so on those
before 1981. These can have a wider right side of rear wheel spacer installed, and BMW even sells such,
but that may not help enough. For the front tire, which came as a 3.25 x 19 (and in some cases, like the
R65, 18"), you can usually go to 3.50 x 19 or metric 100/90, but you might have to use a later seventies
fender mount. More much later in this article on that. A 90/90 or even 100/90 on the front, and a 110/90
on the rear is very common and USUALLY WORKS WELL on Airheads. In some instances SOME 120
will fit the rear; BUT, sometimes (pre-1981 for instance) one has to get the wider 10.7 mm spacer for the
right side of the rear hub...BMW part number 36-31-2-301-737. That spacer change has been needed
sometimes for 110, but not often; more often for 120. Stock was 9.2 mm, and was 36-31-4-038-142.
The spacers are VERY easy to install, and do NOT affect bearing preload. A few 120 rear tires fit rather
tightly on drum brake models; that is, the wheel with tire mounted to it is a bit difficult to install, and at
least deflating it is needed. NOTE: BMW uses 'top hat spacers', or call them brimmed spacers,
at various places in the bikes. You will find them at the swing arm sides, and the wheels.
One top hat spacer, part number 36-31-230-322, was originally an exceptionally WIDE hat type,
and this spacer has been sometimes used to space the rear wheel to the left even more. That
spacer is 12.9 mm wide, and the hat is nearly 32 mm in diameter.
In general, 120-18 rear tires on twin-shock airheads are NOT recommended by me, but also NOT
recommended against.... although I certainly have had a lot of them on my various R100RT bikes.
The part number used by BMW for some of the top hat spacers at the swing arm bearings is
different than the almost exactly the same 9.2 mm part used at the wheel bearings.
They are usable however!
BMW modified the REAR WIRE SPOKED wheels for extra clearance, and this was done in the /5 days,
as well as the ST and G/S days, and it was done by offsetting the spokes; details elsewhere's on this
site. While many think that the ST and G/S 3 mm offset change came when the REAR wheel went to
a 2.50 from a 1.85 size, this is not so, it was later on ...after that change.
2. The rear fender can be modified, hardly shows, makes tire changes easier.
http://bmwmotorcycletech.info/RearFenderMod.jpg for a photo.
3. The BMW tube-type snowflake wheels are "WM2" in rim SHAPE. Other articles of mine treat the
use of tubeless tires withOUT tubes. Click here for that link, http://bmwmotorcycletech.info/section6.htm.
It is almost always OK to install a tubeless tire WITH tube into a tubeless wheel...but mentally reduce
the speed rating by one grade, due to heat buildup with a tube.
4. Try not to purchase tires more than THREE years old, date codes are on the sidewall, showing week of the
year and the year.
5. The maximum inflation pressure shown on the sidewall is for normal use, not for inflation to seat a bead,
which is higher, just how much higher is subject to safety concerns. For installing tires I don't go over
60 psi, try to stay at 50 psi, and use lots of REAL tire lube. Generally the manufacturers will allow up
to 50% over the sidewall printing for mounting....be cautious, if a rim explodes you can be seriously
injured. THE secrets to seating a tire are to have the rim bead area CLEAN and SMOOTH, use
LOTS of the RIGHT type of lube (REAL tire lube) and have the tire and wheel (and tube if used )
truly hot from being in the sun! ...AND!!!!....TO REMOVE THE VALVE CORE ....AND ALSO
REMOVE THE TIP IN THE HOSE CHUCK. USE A 125+ PSI 3 GALLON+ TANK ON THE COMPRESSOR
and large inner bore size fittings and hose. ALL THIS SO THE INRUSH OF AIR IS FAST. YES,
the SPEED of the air inflation is a BIG secret! Even so, an occasional tire will prove to be difficult.
6. NEW tires are VERY slippery!.....allow 20-50 miles to scrub them off. I prefer to first thoroughly
brush the tires with a fairly strong detergent and hot water mixture, and then flush them, before
riding on them. I use a stiff bristled old-fashioned floor scrubbing brush.
7. Continuous speed rating is marked on the tire, usually as part of the number/letters of the tire size. Tires
with deeper tread MAY wear longer, sometimes they do not, from the same manufacturer. Deeper tread
tires are generally rated lower in speed, and usually are the better buy for touring. If you do not ride at
warp speeds, an H rated tire may be a much better buy than a V rated, as an example. MAY is the word
here. Sometimes the only difference is TREAD depth....the higher rated tire having a LESS deep tread.
This is not universally so. Another way of stating this, a bit differently, is that a higher rated tire is NOT
necessarily a better tire...for YOU!
Here is a chart of what the letters mean.
Remember, if you install a tube in a tire marked tubeless, reduce a grade):
Letter Km/hr mph
B 50 31
C 60 37
D 65 40
E 70 44
F 80 50
G 90 56
H 210 130
J 100 62
K 110 68
L 120 75
M 130 81
N 140 87
P 150 93
Q 160 100
R 170 106
S 180 112
T 190 118
U 200 124
V 240+ 149 Note that some V or VR tires may be rated for OVER 149 mph
W 270 168
Y 300 186
Note that there is a Z and ZR rated group, they also are over 149 mph like the V/VR
(A) Sometimes sidecar folks will use a tire designed for rear use, on the front. If you do so,
& the tire has a directional arrow, you can REVERSE the tire, so the direction arrow is in the 'wrong'
direction of travel. Some tires are bi-directional, and maybe with two markings for direction,
depending on if used for front or rear.
(B) For sidecarists, 16 inch rims CAN be used for passenger car tires OR motorcycle tires (if rim
width is proper). Do NOT generally use or try to install, a 15 inch m/c tire on a 15 inch car
rim, nor 15 inch car tire on a 15 inch motorcycle rated rim. You MAY be able to use a 15"
car tire if the motorcycle rim is skimmed on a lathe or the car tire is a quite small one.
***PLEASE HEED THESE WARNINGS!!....MORE:
15 inch car tires and 15 inch motorcycle rims are NOT the same diameter!!! 16 and 17
inch seems OK. If you insist on putting a 15" car tire onto a 15" motorcycle wheel, the smallest
tires may work OK, the larger ones are definitely dangerous to mount. YOU CAN HAVE A
CATASTROPHIC FAILURE! NOTE that some sidecar manufacturer's use 15" car type rims.
9. There ARE reasons to NOT screw the tube valve stem nut
to the OUTSIDE of the rim:
(A). No allowance for tube movement if one has a leak, and the tire rotates on the rim some.
(B). If the tube seals to the rim too well, it can trap air from tube to rim, and allow tube chafing.
The purpose of the tube nut is to help DURING installation of the tube...and can be
discarded...or run up to the cap...after the mounting is done. These ARE NOT just my
ideas! I can quote from tire manufacturer's manuals...and a BMW bulletin...on these facts!
(C). BMW has had at least two bulletins out on these valve nuts, and one SI gave an additional
reason to have it up against the cap, that was that improper inflation could cause the tube
to be weakened at the valve stem and if the nut was at the rim, and not the cap, the stem
could disastrously tear out, suddenly. What BMW did not say, was that this comes from
very low inflation AND overinflation during seating of the tire.
My tire repair article: http://bmwmotorcycletech.info/tirerepair.htm has a lot more information on
use of nuts, concave washers, etc.
10. Inflation is usually in psi (pounds per square inch), but some tires have it in BARS. Bar means
BARometric pressure, one bar is atmospheric pressure, about 15 psi. NOTE!! ...manufacturer's, such
as Metzeler, used to have in their technical books, information that during mounting, the maximum
inflation pressure (DO use plenty of tire lube!!) was 150% of the tire sidewall printed value.
Manufacturer's are getting lawsuit conscious....and many now say not to exceed the sidewall
printed value, or 20% or some such. Because 150% can be interpreted by some to be 150% on
top of the original pressure, some manufacturer's changed wording to say 50% increase over
maximum sidewall-printed pressure. You are on your own. I do not go over 50 psi unless I am
forced to, and it is very rare indeed that I go to 60 on a motorcycle type tire. This is NOT an
OK for YOU to do that! An exploding rim can kill you. Seating of modern stiff tires onto
the rim is usually THE problem seen. USE LOTS OF LUBE, on a smoothly cleaned bead
area of the rim and have the tube and tire hot from being in sunlight. MIND the hints I gave,
on having things hot in the sun and using a modified chuck and no valve in the valve stem,
and lots of lubricant.....this really really does work well.
There is an old "Rule of Thumb" that after a considerable number of miles, the cold temperature
pressure in a tire should have risen to about 8% higher now that the tire is hot. That is
generally true, but not all types of tires seem to conform, particularly some belted and radial
types. Still, it can be a useful idea. Where this idea came from is actually the manufacturers
of tires. If the pressure is too low, the tire will flex more, creating more heat, and if pressure
is too high, the tire will not heat enough. Tires require the correct pressure for handling and
life, etc. Sometimes when I relate this, someone will ask about tire temperature. Road tires are
designed to run at ~130°C at the contact point. That is VERY HOT. That was NOT a typo, it IS
degrees Centigrade. That contact point cools off VERY rapidly when you come to a stop, so
you can pretty much forget about trying to measure it; particularly with a non-contact meter,
that many seem to own, that does not respond well/accurately to black tires.
Many TIRE manufacturer's used to tell you the REAL tire pressure to use or try with their tires. Lawyers
probably got involved, and most literature now just shows the motorcycle manufacturer's recommendation......
which may be too low for Airheads (generally BMW recommendations are pretty much correct on the
single sided rear end Airheads and usually any Airhead from ~1985)...and NOT correct, seriously not,
for modern tires on pre-1985.
BMW had recommended tire pressures on a label someplace under the seat & in the owner's manual.
Some later BMW literature upped some of the old pressures to SOLO 32-34 psi, both front & rear. That
pressure is STILL LIKELY NOT correct for YOUR riding, tires, conditions. I have found almost NO tires
that should have 32 psi in the rear! Modern tires NEED higher pressures: 33-36 front;38-42 rear, .
11. Motorcycle tires have had for some time a LOAD index coding, something like 81H. The tires may
eventually get the standard car tire coding of alphabet letters for wear and heat. If you pack heavily,
perhaps you weigh a lot, and you have a passenger.....pay attention to the manufacturer's published
information on loading allowed. SPEED rating is downgraded by one grade if a tube is used in a
tubeless-rated tire. TL means tubeless....does NOT mean you MUST run it tubeless. - means bias ply;
R means radial; B means bias belted. A FEW tires marked tubeless should not be used with tubes.
Ask, and look at the sidewall printing too.
12. Airheads came with a number of different rim WIDTHS and TWO GENERAL SHAPES. BMW used the
WM2 rim SHAPE up until they installed tubeless tires, not officially OK with tubeless tires withOUT tubes.
Many arguments abound about this subject. The WM2 rim does NOT have the 5 degree increased angle
of the flat area inside and the side area...all of which the tire bead rest against. You are ON YOUR
OWN if you fit without a tube, in a snowflake wheel designed for tubes. Rim width and tire size fitted
must be within a range of values in order to not only fit into the fender/brace/etc; and swing arm on the
twin shock models.....BUT...if a tire is too wide for the rim, the tire will tend to roll in turns, making for
lousy handling. EVERY tire manufacturer has a recommended range of rim sizes for each model
and size of tire. Those recommendations ARE correct. Early /5 rims were 1.85" on front AND rear.
Later /5 bikes had 2.15" rear rims. The 1.85" front rim was carried along right up to 1984 on most models.
The R80G/S had the narrow 1.85 front rim, and early ones the 2.15 rear, then came a 2.50 rear. Of
course, those G/S also had a 21" front wheel. Some of the bikes came with a 2.75" rear rim...this was
on the 1978-84 RS, R100S; and 79-84 RT with disc brake rears; the drum brake rear bikes in these
groups were generally 2.50". With the Monolever and Paralever bikes, things changed with the rims
again, with a new rim design, for tubeless tires withOUT tubes, etc.
An EXTENSIVE article on using various rims as tubeless, etc., is HERE:
13. Some have a hard time getting a pressure gauge onto the valve stems of the snowflake rims. There is a
90 degree stem adapter available from BMW, I don't recommend its permanent use though. FRANKLY
I don't use them at any time. 71-11-1-239-258. Any of the stock type, 45 or 90 degree head, pressure
gauges are fine....just check their calibration once in awhile.
For other purposes (than difficulty with using a gauge), BMW also has a steel, chromed, straight valve
stem, for use with tubeless (and for snowflake conversions, but this is NOT officially approved), it is about
$4 from BMW...and is available elsewhere's cheaper. The BMW number is 36-32-1-452-748...and this
part is vastly nicer than a typical small car or yard vehicle all rubber stem. You cannot get a good seal
with that stem, unless the inside of the rim has a flat milled place for that valve stem.
14. Most flats/punctures are on rear tires. MANY can be avoided....by simply putting a LONG mudflap onto
the FRONT fender, the closer to the ground the better. Nice looking ones are available. You may have
to drill some holes, use screws, washers, nuts. What this flap HELPS to do (theory anyway) is to
deflect road garbage being thrown backwards, perhaps standing the debris upright.....and into the
path of the rear tire. Hence, the type that hangs down the furthest is desirable. The truth is a mixture
of that, and the fact that the REAR tire provides the tread-distortion of acceleration and engine braking.
15. Tire dating:
Tire sidewalls have a lot of information. One area shows the manufacturing DATE. On earlier tires,
prior to year 2000, there were THREE digits... first two digits meaning the WEEK of the year, and a
third digit for the year. In the 1990's, there was a small triangle to identify that it was made in the
1990's. Sometime during the 2000 year all manufacturer's changed to the 4 digit system, the first
two digits being the WEEK of the year, and the last two digits being the YEAR. If the tire code was
455, you know the tire was manufactured in the 45th week of a year ending in 5 (but it had to be 1995,
if the triangle preceded). The reason only three digits was originally used was that the bureaucrats
thought that tires would not likely be in service for over 10 years.
There is additional coding you may be interested in. There will be something like the following:
DOT ENYO VLK 1704.
What you MAY be interested in is the two letters after DOT, in this example, EN. These can be looked
up at http://www.harriger.com to find out what factory they were made in. I have PURPOSELY not
listed the exact URL for the specific PAGE in that website, as INTERNAL links do not properly relate
to outside full URL's.
There is a longer DOT code in use now. The DOT coding begins by some letters and numbers. The
first two letters identify the factory. The list is at: www.harriger.com/tiremakers.htm. The last 4 digits
are the week and year, as above. NOTE that while DOT regulations mandate information on both
sides of the sidewalls, you may have to look in two places and on both sides for the ENTIRE identification
numbers/letters. The original reason this was done was, supposedly, to reduce problems with the
manufacturing and mould interference.
16. Recommended and NOT recommended tire vendors. This section is not kept-up to-date.
a. NOT recommended: MAW (www.mawonline.com, Motorcycle Accessory Warehouse).
: Discount motorcycle tire and accessories.
b. OK; but pay attention to shipping charges, sometimes if you buy TWO tires shipping is
free. Pay attention to date codes.
Motorcycle Superstore, Medford, Oregon. Cheaper if order is over $89, free shipping.
SW mototires (no shipping if buying two)
Generally, BikeBandit has decent prices and decent cost for shipping. AMA members get
10% additional discount.
c. Don't forget to do a thorough Internet search; and, do NOT forget about your local
independent service ....and even your BMW dealership.
There is a lot of BAD information, or just plain hype, on the use of nitrogen in any type of tire
for road and off-road use. The facts are, that while there ARE benefits, use of nitrogen to fill tires
is NOT very practical for anything but racing. On the plus side, molecules of nitrogen are larger than
average air molecules. These larger molecules do NOT pass through the rubber used in tires and
tubes as easily as common air molecules. Thus, pressure loss over time is lower, this is particularly
so with higher percentage natural rubber tubes, as opposed to the lower percentage natural rubber,
often just called plastic tubes. On a practical basis, the slower loss is NOT a BIG difference to most.
One factor not talked about much is that nitrogen is available in different percentages, and the very
high percentage version is THE BEST. BTW...CostCo, which does NOT sell motorcycle tires, DOES
use the premium nitrogen.
A plus factor for nitrogen is that it is less prone to accumulate water vapor, and, is very DRY when
installed into the tire, not so the 'outside air' from your average compressor setup, nor a gas station.
Water vapor in common compressed air can lead to rather wild fluctuations in pressure as the tire
heats up, and cools down. Obviously, this is minimized by using clean, dry, air. Nitrogen, due to
its lack of extra affinity for water vapor, delivers a safer, more stable tire pressure, which can be
somewhat important for very high speed driving (much more so at racing speeds). The final good
point about nitrogen is that it does not contain oxygen, which tends to degrade rubber compounds
over long periods of time. The PROBLEM with nitrogen is cost, not easily available, and if you top
off the tire with even a very slight amount of compressed air, especially if the air is not dead dry,
some advantages of the nitrogen is LOST. This is very much LESS SO, if the nitrogen that was
used is a very high percentage type. Nitrogen's good effects work with tubeless AND tubes.
There are instances wherein someone uses a tube-rated tire without a tube. In some instances this
is done with various motorcycle tires, but also done with two special sidecar type tires.... and, there
are only TWO types of these square-profile sidecar tires available, as far as I know. One in 18"
and one in 19", and not from the same manufacturer! (19"=Avon Triple Duty; 18"=Metzeler Block K).
I have tried nitrogen in these tires in these situations, and it appears that tire pressure loss IS SLOWER.
Since the pressure loss from these two tires CAN be more rapid than with tubes, this is something to consider.
Another usage is a tubeless tire used on tube-rated rims. While that brings up a whole story in itself, and
has its own article on this website: http://bmwmotorcycletech.info/section6.htm. I have done some
preliminary testing, and leakage does seem less with nitrogen. The bottom line, of course, is that
almost none of you are going to buy or lease nitrogen tanks for use at home....but some bike dealerships
may be using nitrogen.
18. TIRE WEAR: The reasons for various "strange" tire wear....and why one side of a front motorcycle tire
wears so much faster than the other side...and why downshifting for braking instead of using the brakes
(downshifting for braking lowers tire mileage); and a LOT more, is in this article, which is so good that
I never wrote such a complete article myself: http://www.rattlebars.com/tirewear/index.html.
The only thing NOT well-explained, is why some two people with identical makes, models, and years of
motorcycle, with the same make and model and pressure in their tires, and the same riding habits and
styles....will, or can, have such different tire wear. I'm not going to get into that, HERE.
There are several types. It does NOT have to be on water! The TWO types of hydroplaning that YOU
are likely to be concerned about are called (1) Dynamic Hydroplaning; and (2) Viscous Hydroplaning.
Both occur on wet roads, although the viscous type might be said to ALSO occur on ice. You are
unlikely to be much concerned with the two other types of hydroplaning, except maybe you might have
a passing interest in the fact that if the brakes are used hard enough to STOP a wheel from rotating
(and you are still moving), you MIGHT heat up the rubber at the contact point to where the rubber
REVERTS to its PRE-cured condition, and then it just plain slides, like on ice. Dynamic hydroplaning
occurs when the water in front of the tire can not be moved away from the contact surface fast enough.
The actual science deals with the water pressure 'being rolled up'. That pressure is opposing the pressure
the tire places on the wet surface (the weight of the motorcycle normally on that tire contact with the
surface). Various things have an effect on just when hydroplaning will occur. Effects from:
softness and other factors of the rubber compound; road surface; tire profile; type of rubber;
tread depth. All those things would seem to be 'common sense'; and, yes, they are; but not to the degree
you may think. NASA did a LOT of testing, and their testing has since been re-proven by common
motorcycle and car tire manufacturers, and the results are that a major variable in dynamic hydroplaning
is from the PRESSURE in the tire. The depth of the road surface water NEED NOT be very much at all.
Hydroplaning CAN, surprising some of you, occur with quite deep tire treads ...at a speed, in miles per
hour, as low as 9.9 times the square root of the pressure in PSI. The figure for nautical miles per hour
is 8.6, usually what is seen in various publications, usually not mentioning that it is nautical, NOR that this
is "STATIC speed"...and no explanation). If you are MOVING, the speed is LOWER! These points
are almost never in any articles about hydroplaning! Welcome to Snowbum's anality and verboseness
and providing extra facts. Once hydroplaning starts, it can remain for MUCH lower speeds. You
are in danger of suddenly loosing control, from JUST hydroplaning, on a wet road, even with really good
and deep tire treads, at speeds as low as 45 mph if inflated to 27 psi; and 56 mph if inflated to 42 psi.
If standing water is fairly thick, these speeds are much reduced, although some say there is no
difference...the REASON is that they are talking about CAR tires, or reciting from literature meaning
CAR tires. In any case, note that hydroplaning speed rises ...a good thing...as pressures RISE. This is
exactly backwards to what some riders believe. They think that in rain, they should LOWER the pressures.
Well, in one way, they are correct!...the bike will feel more jittery, less planted, with higher pressures (assuming
here that the higher pressures are higher than the recommended pressures). Since the front tire is almost
always the critical tire, and almost always has the lowest pressure, beware of excessive speed in the
wet!.....you may loose control without using the brakes & much more likely if using the brakes,
even gently). I am well aware that most of you probably think if you LOWERED the tire pressure,
it would either grip better on wet roads, or be less likely to hydroplane. Keep in mind that hydroplaning
is just one factor, and you can easily loose control due to insufficient tread depth, oil on the road or
floating on the water, wind from the side, and a host of other factors. What all means is that you can
loose control at a VERY much lower speed than that for JUST the published hydroplaning speeds.
"Viscous hydroplaning" is the type, at least on your motorcycle, that you might encounter if the road
was rather smooth and the tire getting rather bald. This can occur at very low speeds and VERY low
amounts of water on the road.
If you are or beginning to, hydroplane, it will be like riding on ice. It is my opinion that on modern motorcycle
tires if your tread depth is at least 3 or 4 mm, then the MAIN influence on the speed at which hydroplaning will
occur, is the tire pressure and the thickness of the water on the road. If you never ride in the rain, you won't
likely worry about hydroplaning. It is also true that there are very soft special rubber RAIN TIRES available for
racing. They have special treads, and a lot more, and are NOT part of my discussion, beyond this mention.
The safest thing to do if in the rain is to reduce your speed GREATLY, and be gentle with leaning and brakes.
For common ordinary street tires for your motorcycle, some are better than others in the rain (or, just mildly
wet roads). The manufacturer's literature MAY...or may not.... be helpful in this regard. I can say the same
for anecdotal 'evidence'....that is, can you believe what fellow riders say about a tire? If a LOT of your fellow
riders have run the SAME tire, and nearly the same pressures, and they live in really rainy areas...well, I'd take
THEIR word about the best street tires for rain....over the manufacturer's claims, or from someone who rides
gently once in a great while on damp roads.
GENERALLY speaking, the LONGEST wearing street tires are the worst for rain. BUT, this is not universally so.
Some premium long-lasting street tires are quite good when it is raining.
20. Tire sizes; rear swingarm clearance, ETC:
Much of this information is also posted elsewhere's in this website. It is shown here on purpose....and
expanded upon a bit.
The original tire sizes for all the early Airheads was 3.25 x 19 front, and 4.00 x 18 rear. Some manufacturer's
still make those size tires. For those wanting to go to modern metric sized rubber, the 90-90/19 will fit all the
19 inch front wheels, and the 100-90/19 will fit the earliest models front if the fender support brace is changed
to the later wider type. The later wider fender brace you would want is the 1977-1980 used on the /7 bikes.
The BMW part number is 46-61-1-234-907.
For the 110 or 120 size rear tire, problems will be with the wheel/swingarm/discbrake stay area. Most often,
the 110 size fits withOUT any spacer changes. Either the 110 or the 120 will do for the rear; but I recommend
you NOT get the 120. You MIGHT have to go to the slightly wider right side top hat spacer, which is
36-31-2-301-737. SOME 4.00 rear tires are quite wide (especially Enduro types)! If your rear tire is touching
either the swing arm or the brake stay at high speeds, then you almost surely will have to use a wider spacer.
That TOPHAT spacer I am speaking about is located in the RIGHT side of the rear wheel of twin-shock
absorber bikes & is easily removed & changed. The wider spacer may not be needed on 1981 & later, but I
HAVE seen it required. There is a VERY MUCH wider spacer available too, see earlier in this article.
The stock spacer is 9.2 mm wide, the 36-31-2-301-737 is 10.7 mm wide. On some bikes, with some tires
(Continental TK17 in 110 was the worst I have personally tried, other than enduro tires in 4.00), the tire will
rub the swing arm at high speeds (~85+), the spacer was a must....unless you liked the rubber smell, etc.
Usually most 110 tires fit without needing the spacer, say on an early eighties RS/RT. On some rear disc
brake bikes with the rear tire being a 120, I have had to ADDITIONALLY put a spacer on the left, a common
very large washer called a Fender Washer, available at most hardware stores. Strangely (or not) that has
mostly been when using an EARLIER snowflake wheel. These snowflakes can LOOK the same, but are NOT.
That spacer moves over the brake stay very slightly...avoiding any possibility of tire rubbing at speed.
The swing arms vary a bit, even in the 1980-1984 era, another reason for sometimes needing the spacer(s).
When you change the right side tophat spacer to the longer (wider) one from BMW, that does move the
wheel-spline-engagement very slightly to the left....by about 1.5 mm, which is a small amount. There are
naysayers that think the wear on the rear splines will be such that you cannot go back, and that is not really
so over the long run, nor does the tiny shortening of the spline engagement have any large bad effect on
spline life. Changing the tophat spacer does NOT affect bearing preload.
The snowflake rear wheels on the RS and RT are slightly wider in rim width than the drum brake models.
The disc brake snowflakes are 2.75" rim width (measured at the official point for tire contacting the rim);
and the drum brake snowflake rims are 2.5". This slight 1/4" difference also makes the RS/RT disc braked
bikes rear tires a bit wider...and puts a bit more rubber on the road too.
Don't forget that the under-seat and owner's booklet values for tire pressure are TOO LOW for modern tires.
Try about 33-34 psi front and 38-42 psi rear.
21. Bridgestone tubes are of good quality.
22. For TUBELESS TIRES being used on TUBE TYPE RIMS, the rim hole is 8 mm. If you do not wish to enlarge
the rim hole for a standard pull-in type of stem, then there is a special valve stem that is available, even from
BMW, that seals at the inside of the rim by means of an O-ring built into a recess of the stem unit. The
stem area of the rim, inside, must be machined flat for this to work well.
This section was added to try to explain things often poorly understood...if at all...about such as tire
profiles, sizes, differences in construction, warming-up effects, differences between road, track,
and racing tires, etc. Some of this information came from Harriet Ridley, a moto-writer in U.K.,
but the information has been added-to, deleted, subtracted-from, edited, etc., ...by me. So, if you
see some familiar wording or sentences, they might be attributed to Harriet:
Some of what you read below is very basic. READ IT ALL!
Tires work with your motorcycle to determine how hard you can brake, how fast you can accelerate and
how much you can lean and how well they keep you from loosing control. The tire and how you use it
which includes inflation amount, determines how far you can travel before they wear out and let's face it,
tires aren't cheap. There's no optimum tire for every situation. Each tire is a complex trade-off between grip,
longevity and handling.... and R&D is poured into finding the perfect compromise for a given situation. With
three aspects responsible for a tire's characteristics - compound, carcass and profile; besides, of course,
inflation pressure and road conditions including surface and temperatures; - there's a lot for engineer's to work with.
If a tire were made from pure rubber it would wear EXTREMELY quick and would never take the required
weight. Instead, the 'rubber' (often a synthetic equivalent) is mixed with carbon black to make it tough and
resilient, then baked at high temperatures and mixed with what could be dozens of chemicals and even
silica/sand. Varying quantities and types of these determine the compound's softness and its optimum
operating temperature and its wear.
The tire grips by pushing itself against the surface so the softer the compound, the more it will grip. The softer
compound will also be more abraded by the road, wear faster, as well as generate more heat by flexing more.
Regardless of compound, there's a temperature at which tires operate best for the purpose they were
specifically designed for. Unless a tire reaches its optimum temperature the compound won't soften
enough to provide the intended grip - hence the use of the silica in road compounds to ensure a certain
level of grip in cold, damp conditions and why it is important to warm up your tires carefully. Silica can
also INcrease tire tread life. There is also a temperature at which all tires will overheat. After
construction a tire is cured in an oven at a certain temperature for everything to stick together. If your
tire goes over that same temperature for too long, it will de-cure; at first it squirms and loses traction
as it breaks down chemically, then it delaminates as it breaks down physically. So each tire is carefully
tailored to suit its intended purpose.
The compound is designed for plenty of grip at constant, high temperatures
reached by the extreme pace maintained on a track: hard acceleration, hard braking and high corner
speeds. Because it is designed to live at high temperatures the race compound will also take longer to
reach its peak. If you use these tires on the road and even if you ride quite hard, you'll be forced to
slow down for traffic and stops, etc., and every time you do so the tires will cool off and take a long
time afterwards to even approach their required temperature again. Keep this up and the tires will wear
fast and shed rubber through cold tearing; so they may look like they're being used hard, but in fact
they're disintegrating from misuse.
Each time a tire goes from hot to cold it's re-curing itself to become harder, as chemical
oils used in the tread to maintain compound are released (hence, in some cases, the blue color you
sometimes see on a tire's tread after hard use). While this is minimal on a road tire, it becomes more
extreme on race compounds. Specialized race tires are designed to go through only one heat cycle
before compound deteriorates, while track-focused tires are a lot more sensitive to heat cycles than
their road equivalent. Hence tire warmers not only bring tires up to their required temperature, they
also maintain a constant temperature between races or sessions to minimize heat cycles. ROAD
tires are designed for all the heat cycles you might need.
The carcass gives the tire its required strength (it's more resilient on a road tire, and how
much the carcass lets the compound flex affects heat generation) and its rounded shape. But because
he tire's contact patch is flat the tire has to compress and distort where it meets the ground. This
shape-changing means some of the rubber has to slide across the road to achieve the new shape,
causing wear, while the constant flexing of compound and carcass at this point generates heat.
The old-style cross-ply tires used many layers of plies molded at an angle to give the tire strength.
But the sheer amount of material used made them heavy and generate a lot of heat, so harder
compounds had to be used to maintain the right temperature.
As bikes became faster, lighter and more agile, tires had to follow suit. Bias-belted tires appeared as
a step on the path to radial heaven, and they're still in use on big heavy bikes where sidewall stiffness
is more important. But radials broke new ground thanks to clever layering of fabric. A radial tire is not
only lighter and more responsive, it also runs cooler as the tire distorts more easily, a special type of
distortion and angle that seems to be opposite than flexing increasing heat that I have previously
described (and with running tubes). Running cooler means you can use a softer tread for better grip
with no increase in wear. The shape of the carcass's crown radius also dictates the way a tire handles,
which together with the sidewall determines profile.
On a 120/70-17 front tire, 17 is the diameter of the wheel rim in inches, measured at a
particular point of the sidewall area of the wheel; 120 is the width of the tire in millimeters, and 70
is the percentage height of the sidewall against the tire's width - so the sidewall is 84 mm tall. The
higher the sidewall, the more slower steering but good stability. Lowering the sidewall by 10mm to
a 120/60-17 the tire acquires a steeper profile - it is more 'triangulated'. The results are quicker
steering and more grip when leaned over, but anywhere in-between straight line and transition from
upright to lean angle is less stable. The carcass's crown radius also shapes the profile.
The sidewall also acts as suspension for the tire and comes in varying degrees of stiffness: a big
heavy touring tire needs the thick bead filler found in the sidewall of touring tires for added strength
and stability. By reducing the height of the sidewall, the tire is less capable of absorbing surface
irregularities and tends to hop when cranked over, causing the bike to understeer. A race
chassis with high quality suspension copes well with a quick-steering 120/60 or a racing
slick's more radical profile and flexible sidewall, but fit racing slicks to a road chassis and
the bike becomes un-settled. As a result road bikes and Superstock racers would generally
opt for the more suitable 120/70 front tire.
Rear tire size also affects performance: a 180 section will steer quicker, while a 190 will last
longer by coping better with power battering.
A road tire will greatly outperform a race tire in terms of acceleration, cornering speed, braking,
durability and stability ....over the course of a road trip.
A tire's compound (tread) is molded onto the carcass. On a radial tire the
carcass is typically made of two plies with strands usually of steel or aramid (that's Kevlar):
the first is a radial ply that runs at 90° to the tire's rotation (folded under the steel bead),
while the second runs in the direction of the tire's rotation to minimize expansion at speed.
The top two plies are cross-plies (with usually Nylon strands) placed at an angle to add strength.
The bead that you'll find on all types of tires holds the tire to the wheel rim with a 'rubber'
bead filler to strengthen the sidewall.
• Low pressures cause tires to move around and generate heat, while high pressures will reduce
the contact patch and the tire will struggle to warm up. Always check your pressures from cold
(cool to baby bottle temperature). NOTE that many manufacturers, due to lawyers and thread of
lawsuits, will simply repeat the motorcycle manufacturer's recommendations for street riding tire
pressures; BOTH of which can be WAY wrong for YOUR tires and riding. WAY WRONG!
Typically and generally, the real tire pressures you should use for street riding on OLD BIKES
will be HIGHER than the manufacturer says. This is especially so for such as early Airheads,
which used the old soft and ribbed tires, like the Continental RB2/K112. For modern tires,
pressures under 30 or slightly over 30, will be QUITE WRONG for best handling...and life too!
You will probably find that your bike that was specified for those tires, say 4.00-18 rear and
3.25-19 front, should be run at 33-36 front, 38-42 rear, depending on speed and loading.
• New tires need careful scrubbing in to get rid of the slippery mould release agent used at the
end of the production process. Some say up to 200 miles. MY experience is that 50 miles is
more than good enough, but if you scrub the tire after it is mounted and inflated, with soap and
water, then flush it off, you can go do less. Just be particularly careful during initial 20 miles,
and be sure your break-in miles include some steeper turns....head into them gently until the
tires are scrubbed in!
• A slick's uninterrupted compound (or tread) optimizes dry grip, but it's unable to clear standing
water and debris. Hence a pattern is molded into a road tire's tread. A tread pattern also generates
heat by flexing ('block movement') and is usually no more than 8 mm deep to prevent weave and
excessive heat build-up. Mind what I have said about depth and tire rating (V, H, S...) much
earlier in this article, and tire mileage.
• Race tires are available in different compounds and mix-matching can provide an ideal compromise
between grip and longevity. A softer tread is used on the front for better grip while the rear gets a
harder compound to cope with the power battering. The front is also sometimes fitted with a flatter,
more stable profile while the rear can be more triangular for quick steering. Manufacturers do
all the work for you on road tires so don't mix-match on them, unless you know what you are doing.
• Specialized race tires get different compounds on either side of the same tire, so where a track
has a predominance of right-hand corners the compound will be harder on the right but softer on
the left. Similarly, Bridgestone's dual-compound road tires get softer edges for good corner grip
with a harder middle to reduce tires squaring off with the accumulating non-cornering miles.
01/28/2004: initial 'dated' upload after final revisions.
02/03/2004: expand information on handling and tire size uses slightly
02/09/2004: add #14
09/01/2004: Update article, with better clarifications and stem part number, etc.
04/03/2005: changes in emphasis throughout, and add some hyperlinks and add #15
04/20/2005: Add tire make and model description information in more depth
05/13/2005: minor updates, primarily on the top hat spacers.
08/07/2005: add comments on karoo and scorpion and info on Discount m/c tire and acc.
08/13/2005: update section 4
09/24/2006: add 17
12/15/2009: revise and add more tire model information
05/12/2010: Revise for clarity, combine some areas, add more information to what is now 23.
05/31/2010: Add 24.
12/22/2010: #25 finally added/updated.
12/23/2010: updated tire recommendations
03/14/2011: add #26
06/20/2011: Finally got around to updating my recommendations for dual-sport tires
06/28/2011: Add more information on tire flexing, contact temperature, use with tubes
08/04/2011: Correct my math on hydroplaning, add a bit more to that info too; combine into one place.
04/25/2012: Update tire information slightly, clarify minor things here and there
06/17/2012: add Bridgestone tubes; and, update vendors
07/11/2012: Minor updates on Roadrider tires and add 28
10/14/2012: Add QR code, add language button, update Google Ad-Sense code, minor other stuff such
as updating URL in #24. Language button removed later, as had scripting problems with it.
01/22/2013: Updated article to give more information, in depth, on tire types and uses, its own section.
04/23 & 24 /2013: Minor updating, tire pressure reference, etc. Edit to reduce SOME duplication and
improve clarity.....here and there.
09/20/2013: Add Conti-Attack listing and info.
10/07/2013: Add tire photos, and a few comments here and there
04/08/2014: Update the entire article. Fix typos, add information, fix numbering system, etc.
04/23/2014: Update various places. a bit more 09/25/2014
11/02/2014: Add link to #5
05/24/2015: Add note to Avon RoadRider's; and additional note regarding steel plies pros and cons, on 05/25/2015 and
06/12/2015. Testing notes on 06/19/2015 and 06/26/2015.
10/02/2015: Updated for extensive testing on Roadrider's.
11/04/2015: Updated for clarity.
11/14/2015: Heindenau review. Clean up article some, with fresh formatting, more concise statements, on 11/20/2015
© Copyright, 2014, R. Fleischer
Return to Technical Articles LIST Page
Return to HomePage