Tubeless versus Tubes
whole story (?), and then some...
INCLUDING tire tread performance, tread life, and various other things you may not have thought of;
particularly for those contemplating using the tube-type BMW Snowflake wheel as tube-less.
© Copyright, 2014, R. Fleischer
section54, subsection 6
This article will discuss
in depth: Rim shapes (and BMW rim shapes); using tubes (or not) on tube-type rims; tubeless
operation; repairs; arguments for and against using tubes with
rims designed for tubes. Other articles on this website have further information on
these subjects, and much more, such as http://bmwmotorcycletech.info/section5.htm and http://bmwmotorcycletech.info/tirerepair.htm
Here is a link to an article that has enough math (but enough photos too), from a Goldwing'er (Honda Wings have somewhat unique rims) to spin your head, for the nerdy amongst us. Fine if you want to scan the article, but do see the second part of the article....and then REPEAT that look-see.
That article has extensive vector and other diagrams, which may bore you....but, also has some conclusions about contact size and pressures/forces, that may well astonish you. When you read it, keep in mind what REALLY happens when you are cornering..............and....THINK....about the effects if you change a tire size....from, example, a 90/90 to a 100/90; or, 3.25-90 x 19 to 3.50-90 x 19, or similar change from 4.00" to 120 metric, etc.
That is, think about what REALLY happens when you go to a larger size tires (larger width and/or profile change). You may be very interested.
The below article will present data, discussion, & arguments, for tube/tubeless tires and tube/tubeless rims.
Some of the concepts/discussion may require reading one paragraph, and then thinking about it. It is UNlikely that readers will be able to just read this article straightaway-through, and gain the information I wish YOU to have.
There are folks (including some that I highly respect) that say you must ""never"" run any sort of tire without a tube on wheel rims that were not designed to be run as tubeless. I am personally not 'that much' against the practice. What I believe is not the pertinent thing...what IS pertinent is that YOU gain a full and complete understanding of all aspects & be able to make your own decisions.
I will try to inform you herein with UNbiased information. There ARE a lot of misconceptions, wrong-thinking, failure to be open-minded enough to see the whole picture, etc.
There are also real reasons to do what the manufacturer of tires, tubes, rims, and motorcycles too!....say to do...which, generally, are to not use rims designed to be used with tubes, as tubeless.
There are also things not at all widely known. Keep in mind that manufacturer's are not at all interested in long-winded information, like in this article you are reading. Such verbose information would tend to cause them a lot of labor in further explaining things, as there are always people who 'need to contact the manufacturer' to make specific points, commentary, or have the makers provide additional information, etc. Thus, manufacturers make simple easy to understand statements...do this, or, don't do that. Their company lawyers would agree with that attitude.
Motorcyclists & sidecar/trike drivers do all sorts of non-standard things. Car tires, wide rims, change of rim diameters, LOTS OF "ETC.".
If it was really so vastly UNsafe to run tubeless tires withOUT tubes on motorcycle wheels, how come sidecar rigs, which produce SIDE FORCES that can be EXTREME (2 wheelers do NOT have anything even close to those forces), do not have lots of accidents with blown tires, tires coming off rims, etc....? I'll try to answer some of these types of questions in this article.
Sidecarists sometimes, depending on the situation and equipment, install tires in the 'wrong direction'. Ever notice that NOWADAYS many tires are marked on the sidewall as to what usage is (rotational direction), but SOME tires are marked for one direction OR THE OTHER, depending on if used as a front, or a rear.
THINK!!! These are only two of the many variable uses.
That MANY use tires and rims in all sorts of non-standard ways hardly means that 'anything goes'!!
There are also many levels of 'safety'.
Did you know that some have raced Airheads on paved tracks, at high speeds, using BMW Snowflake wheels that were specified for tubes only? Did you know that arguments that tires greatly expand in diameter at high speeds and thus will be likely to have the tire tread move to the center of NON-safety rims, and loose all air very suddenly, is FALSE? In fact, tires mostly expand in width at speed/temperature, and that is typically not any factor in a tire moving to the center of the rim.
Tube vs Tubeless, from several directions:
The primary method by which a tire 'becomes unglued from the rim' is from a massive bending of the rim from the tire hitting a large object in the road.
THAT can happen with tubeless....or tube...type tires/rims/etc.
The 'safety' bump in a safety wheel, as used with tubeless rims, does not prevent air loss from a bent rim. It does help prevent a fast air loss that would occur if the tire became un-beaded, and would otherwise have moved to the center.
(1) Easier on-road tire repair. I think THAT is the PRIME REASON. Tubeless tires MAY loose air from simple punctures much more
slowly. With tubes, a puncture MAY be similar, but they usually leak faster from a puncture, and thus HAVE TO BE FIXED by a
patch, which typically means wheel and tire removal.
(2) Possibly reduced weight, which means slightly better handling and mileage.
(3) No need to carry a spare inner-tube(s).
(4) Possibly deeper tread on some tires, as tubeless tires can run cooler, so tread might be made deeper.
(5) Without a tube, the tire temperature is less, and the tire tread may last longer; or, a better rubber compound could be used.
Not all that often do folks also say that they know that tubeless tires with a seriously bad puncture should be REPLACED, not repaired (or, repaired only very temporarily, and ridden at low speeds, until they can obtain a NEW tire). OR, they know, and ignore this.
I think it reasonable for me to state that I have mixed feelings about all these things that have been mentioned so far in this article about using tube type rims without tubes. While many have ridden on tubeless tires without tubes on tube type rims quite successfully and safely for many decades & hundreds of thousands of miles, MY CONCLUSION IS THAT IT IS LESS SAFE.
It is only reasonable here to point out that motorcycling, in itself, is a more dangerous thing to do, that to use most any other form of transportation. Humans like to do certain things are dangerous. Perhaps the better statement, here, might be: What is YOUR level of safety? Do you wear All The Gear All The Time (ATGATT)?? If not, what is more dangerous, not wearing ATGATT, or running tubeless on snowflake wheels? OR, is it really fair to submit that question at all? Would this argument be better if I put it in other terms?
The primary method by which a tire 'becomes unglued from the rim' is from a massive bending of the rim from the tire hitting a large object in the road.
When I started riding there were no such things as tubeless tires for motorcycles (let alone cars). That means that the inner walls of the tires were not officially fully sealed to prevent air loss. The truth probably is something that SOME tires really were sealed rather well on the inside, and might have been useable as tubeless......but we never thought of it....or, if we did think about it, no one I knew had tried it.
Tubeless tires are NOT a recent development, at least not for CARS. Although invented and patented decades earlier, it was ~1955 that tubeless tires became mostly standard on automobiles. Before that time, tires required a separate inner tube which failed (besides punctures) now and then because of incorrect tire fit, friction between the tire wall and inner tube generating excess heat, etc. Tubeless tire technology does away with the need for an inner tube, and it is, REALLY!... accepted by the various manufacturer's, that tubeless tires INCREASE safety (at least on rims designed for them, as the manufacturer's don't want to discuss it further). ONE of the reasons is that a simple puncture releases air more slowly, than a tube (usually).
If a tubeless tire (no tube installed) gets a small puncture, air escapes only through the puncture hole, leading to a slow and typically gentle deflation. The actual point of DEflation where YOU feel something may be wrong, will vary. This is due to the various types of tire construction, sidewall stiffness, your speed and loading, etc.
Conversely, while an inner tube could potentially burst like a balloon, leading to a more rapid deflation of the tire which could result in sudden loss of control of the vehicle, that was not all that likely. That was an argument some gave, not considering the exact circumstances....which, for that, would PROBABLY be the tire coming off the rim or partially, perhaps due to a large rim bending, that allowed the inner tube to protrude and be gashed badly for a fast DEflation. One argument in favor of tubeless tires was that a punctured tube, used inside a tire mounted to a tube-type rim, will almost always leak faster...but no proof of that idea was furnished.
NOTE!....A burst-balloon effect could not happen if the tube remains inside the tire and is not bulged out from under the tire bead.
If the tire bead becomes disconnected from the rim's bead area, and the tire bead moves inwards, then the tube might bulge out, perhaps the rim or even the tire bead itself would cut it, causing a very fast deflation, from such a ballooning effect. That idea needs to be dealt with, I will attempt to do in this article, amongst other ideas. NOTE that the tube could bulge out from the tread from a seriously damaged rim or from enough DEflation to allow the tire bead to move inwards (assuming no ridge in the rim construction that prevents this...or MIGHT prevent this...). The 'safety bead' or safety-bumps, in a tubeless rim are supposed to prevent the tire bead from moving into the rim's center.
Fast exiting of the air pressure in a tubeless tire is also possible, more or less depending on the rim; and, of course, any rim damage. Manufacturer's have sought ways of keeping the tire bead in contact with the rim area, even for rather extreme instances of the rim seriously bending from such as a large pothole, or the tire hitting an object in the road. While tire beads and rim shapes have changed, with improvements for bend rim problems, there is no common method in use, nor has one ever been widely sold nor promoted, to keep any type of tire 100% in contact with the sidewall area of the rim, no matter what problem occurs.
1. Cars: Rim is VERY seriously bent or cracked/damaged, perhaps the rim is even totally broken into pieces due to impact. The rim damage, and escape of air from the tire, is not likely to be any problem for loss of control....the accident has already caused that loss of control, more or less.
2. Motorcycles: Rims are lighter (or, think of them as less strong), easier to bend from road debris, rarely crack badly, but that is possible. Compared to cars, loss of control in an actual collision accident may be total loss of control (impact with another vehicle, striking a deer, etc.). However, hitting debris in the road can cause loss of control or momentary loss of control, or hardly any such; but the bending of the rim might be enough to let all the air out quickly from a TUBELESS OR TUBE TYPE usage.
MOST motorcycle flat tires come from a modest to slow loss of air from a simple puncture. Loss of control, would, in my estimation, be rarer, as almost always there is an indication of mushiness and weaving that considerably precedes any complete loss of air. It is fairly rare for a rider to lose control.
Manufacturers tried rims with various angles to the bead area. They also put bumps in the rim so that the tire would not likely be able to move into the center area of the rim. They also tried different rim shapes in the center of the rim. NOTE that there are TWO general and common types of 'bumps' to prevent the tire bead from moving into the center of the rim, and ONLY the type with a bump or ridge just a bit inside of the mounted tire's bead area, will work to help keep the tire attached to the rim bead area. That type of rim is generally known as a Safety Rim. Bumps or ridge positioning do NOT totally prevent (as some think) the tire from becoming disassociated with the rim bead area, thus, even with a tubeless-designed rim, it is possible, on having a puncture or rim damage, to have the tire lose air quite rapidly, perhaps less likely (no statistics found by me). Many have argued that the rim bumps or ridges prevent fast loss of air on a tubeless tire, and that is obviously not so, but they can be 'helpful'.
Thus, my conclusion is that many who say disasters are about to come upon one who uses tubeless tires without tubes on a tube-type rim, are not, or may not be, thoroughly thinking things through. The tire manufacturer's will all say, in their literature, not to do this. If I manufactured tires, I, too, would tell people NOT to use tubeless tires as tubeless on tube type rims. BUT....really....just what IS the REAL safety difference? THERE IS SOME...but just how much?
My personal conclusion, and I want to make it very clear that this is NOT ADVICE: using a tire without a tube on rims that are not designated for such use, is somewhat less safe. How much less, over-all, I do not really know. It is very difficult to find real data.
BTW...in your riding career, how many times have you hit something in the road large enough to cause a fast loss of air from a bent rim? What about any of you reading this that have been using tubeless tires without tubes on tube-type rims?
What about tubeless tires on tubeless type rims?
It would be answers to questions like those, and maybe some other questions, that MIGHT give some direction as to what any safety change REALLY means.
THINK! We all know, and it has been proven over and over, that more lights added to a motorcycle, and use of reflective clothing and certain bright colors on a helmet, ETC.......all seem to reduce accident rates. But, is there a limit or some point on some accidents curve, that shows how much gives how much better protection.....are there limits? Would using tubeless tires on tube-type rims, without the use of tubes.....be as less safe as, perhaps, not having the brightest color on your helmet? Not having ...and how many....extra rear lights? What about a headlight modulator?
WE DO NOT KNOW...OR, DO WE?
I hope I have presented some ideas for thought. I am not promoting the use of no tubes in tubeless tires on tube-type rims, but I sure would like there to be a REAL discussion, or at least some sort of thinking, about safety depths.
This is from a 1979 R45. Snowflake. Note the
center drop and its curve, note the lack of any
bead holding bumps. This is NOT what has
been generically called a "safety rim". This is a WM.
Below is a 19" front Snowflake wheel, basically the
same as the above wheel in design.
Flat bottom type of rim, similar to above wheels,
except for the flat bottom area, and that there is
knurling for the tire bead! What do YOU think those
knurled areas really are for or really do? Keep the
tire from rotating as the inner tube looses enough
air, and forces are trying to rotate the tire, and maybe
rip the tire valve off the inner tube, releasing air
faster? What is YOUR idea about the knurling???
This next group is of safety bead/ridges styles:
Note the lack of any knurling. Maybe tubes are
Flat bottom. Same basic rim design as the R100GS, see photos above.
These 3 above photos are Morris Mag's, rear wheel, for Airheads
NOTES: There are many types of rims. One popular one called an MT is nearly identical to the WM-non straight shoulder type.
The CP type, see above and also below to right, has a reverse taper seat. This type is/was,
as far as I know, used only on some BMW's, Moto-Guzzi's, and Laverda's.
Note the HUMP on the TL-H2. Be sure to read 3. below.
REPEATING!: There is a rim shape called MT. It is for tube or tubeless use, depending on what the manufacturer
of the vehicle says. The appearance of the rim is the same as the TL-H2, below, withOUT the bump!
I can provide the engineering book from such as Metzeler, showing this!
SPECIAL NOTE!....in the TL-H2 sketch, above, the BUMP in the rim is generically shown. The actual bump or ridge might be just barely inwards of the tire bead when the tire is mounted and sealed to the rim; or; that bump could be as shown in the sketch, where the purpose is to prevent the tire, which might have disassociated with the rim, from moving inwards to the well area. A compromise is usually made, and some rims even have had both bumps/ridges, or combinations. If a tire moves to the center of the rim, the loss of air will always be very rapid....on any type tire not containing a tube. Note also, how 'easy' it would be for a tire using the TL (not TL-H2) to move into the center area.
Especially not how the CP type rim will help keep the tire association with the rim. If you think about these sketches, and think about what REALLY might happen under several circumstances of using and not using tubes, you just might get the idea that a CP rim WITH bumps or ridges, might be near-ideal.
For the NERDY: Metzeler says that if you use a TL-H2 rim, with a tube, it must be a Metzeler tube. They did not specify why. I think it due to the higher safety of a natural rubber tube, and the Metzeler tube design at the core.
The MTH2 rim is often used on OFF-ROAD motorcycles, where the rider may, under some circumstances, use a vastly lower than normal tire pressure. That is why GS bikes use them.
OK...now that you have plowed through and read all that (and likely gotten confused)......below is the easier (?) to understand information...on what you need to know.
Part II, the rest of the information:
these things are MY personal interpretations/ideas; read & do what you want, at YOUR RISK,
I have to admit that I did not expect this....I EXPECTED more change than I found. What I DID find was that the tires were just a bit more slippery feeling on very cold roads in very cold weather (this I expected), and that measured tire wear was REDUCED (THAT I expected).
2. HINT: NEVER fail to use
tire talc when installing a tube; rub it all
over the tube and inside of the tire with your hands....this allows the tube to
move about a bit, avoiding excessive friction against the tire;
and also helps the tube, upon installation, to avoid any folding.
3. Almost all tires marked tubeless, are OK for use WITH tubes at a reduced maximum speed; per the manufacturer's. Exceptions MAY exist in trying to use RADIAL tires. As a general rule, I suggest you do not use old-style radial tires on your Airhead. You generally will not find old-style radials that fit your Airhead anyway. If you do try an old-style radial tire, approach handling with slowly increasing steps of aggressiveness and speed, until you know what the tire and motorcycle will do. I suggest you adjust the steering head bearings carefully, for just a trace of weaving at maybe 25 mph, before doing radial tire testing. This is a good adjustment for any tires on an Airhead. There are now 'radial' tires specifically made to work with old bikes like the Airheads. You might be interested in trying them, preliminary reports are GOOD, but tire pressures seem to be a bit more critical, IN MY opinion.
4A. Tires marked tubeless are supposed to be specially made to ensure they hold air for long periods of time. This is typically done by a special coating on the inside of the tire. Talk of special bead areas, etc., are WAY exaggerated. Tires not marked tubeless MAY loose air if not used with tubes, as the they could be porous in tread or sidewall, or bead. I have seen tubeless tires hold air for a long time on tube-type rims; and have seen others that would not hold it long. Mostly what I have seen is that the loss is quite slow, and weekly topping-up is adequate; pressure loss not usually being much more than normal found if using 'natural rubber' tubes. Tire pressures are supposed to be checked before every day's ride, right? There are plenty of tires that are not supposed to be used as tubeless, still being made, particularly for off-road use.
SOME folks have used the snowflake cast wheels with tubeless tires, and installed a tire sealant; and had good success in greatly slowing any air loss and have had the sealant work well for them with punctures. MANY have had hardly any air loss over time. Some types of tubes, whether used with tubeless rated tires or tube-type rated tires, WILL lose pressure slowly, compared to the 'plastic' type tubes...but the tubes said to be 'natural rubber' are probably much less likely to be ripped from a puncture.
4B. Purposeful off-road tires are, in the majority, meant for use with tubes, and most of these tires do not have any interior sealing coating. These tires may be used at times as low as 5 or 8 pounds of pressure. Avid off-road riders typically have other methods in keeping tires on the rim, besides special rim bumps/clamps, when using very low pressures.
When installing a tube (tubeless or tube type rims), normally do NOT leave the mounting nut against the rim.
There reasons NOT to screw the tube valve stem nut to the OUTSIDE of the rim, although that is done, although loosely,
DURING INSTALLATION OF THE TUBE, TO MAKE THINGS EASIER:
(A). The tube could fail to release air from between the tube and inside of the tire....which it is SUPPOSED TO DO normally
in use & the tube could chaff, & fail early. This is particularly so if you did not rub the tube & tire insides with tire talc.
(B). Leaving the nut against the rim defeats the safety of allowing the tube to be able to move slightly, upon a flat occurring.
Run the nut up against the cap, or throw it away, or put it in your tool tray....Some tubes are sold with that nut, and the
purpose is TO HELP DURING INSTALLATION OF THE TUBE/TIRE. Restating this: Using the nut against the rim
does not allow for tube movement if one has a leak, and then the tire rotates on the rim some.
(C). 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 & a BMW bulletin on these facts!
(D). BMW has had several bulletins out on these valve nuts, and one SI gave an additional reason to have it up against the cap,
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, and I will, was that this comes from very low inflation
AND over-inflation during seating of the tire.
(E) TUBELESS TIRES are, as you have seen in this article, sometimes used on TUBE TYPE RIMS. The stock tube-type rim hole
is 8 mm. If you do not wish to enlarge the rim hole for a standard pull-in type of tubeless stem, 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.
***There are those, often sidecarists, who seal the tube-type stem with rubber doughnuts or by other means. Sidecarists
do lots of things that some may consider wrong (or, otherwise unwise).
13. Snowbum has, on two of his Alaskan adventures, installed tubes WITH rubber washers and
14. The snowflake tube-type wheels will handle major rim denting and still hold air, if tubes are installed as they were designed to be. HOWEVER, there have been numerous reports of very serious rim bending, with NO problems with tubeless tires, without tubes!
Thus, considering everything I have mentioned so far in this article, there is NO clear-cut 100% answer, in MY opinion, on whether or not....it is safe, or safe enough, or not safe, to remove the tubes from tube-type snowflake wheels.
1. SOME manufacturer's tubeless tires and tube-tires have slightly
different beads, but I have been TOTALLY unable to get DEFINITIVE information,
and my personal inspection has not shown enough difference to make it more
than a minor mention. The flat portion of the tubeLESS rim just inside the bead
is usually a bit wider (depending on the particular tubeless rim design), and I have previously noted the angle differences. I do NOT think this any major thing.
2. When any tire containing a tube gets a bump big enough to damage the rim severely, you may well retain air with a tube, and less likely to without a tube. This does depend on the type of rim construction, and where any 'safety bumps or ridges' are located....and, the shape of the drop center or curved center of the rims. There is also the rare event of a tube bulging out from underneath the tire bead, being cut by the rim.
As a general rule, I usually advise against any tubeless tire withOUT tubes on tube-type snowflake wheels. I think that such use is SLIGHTLY LESS SAFE, OVERALL, all things and conditions considered, than WITH tubes. How much less safe? Well, maybe very little, overall, in practical use. You are totally on your own in this regard.
NOTE!...this is an OFFICIAL DISCLAIMER!:::
.....I am NOT advising that it is, in ANY way, safe...or not... that you run tubeless tires withOUT tubes....on your tube-type BMW Snowflake wheels! You are on your own in doing modifications...I am NOT responsible, and I am not advocating changes to the wheels, nor using tubeless tires without tubes on wheels BMW did not intend that for.
I am simply trying to inform you of how things work, what others have done, and the caveats...as I know them. This is a legal disclaimer!!!
© Copyright, 2014, R. Fleischer
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