Snowbum's BMW Motorcycle Repair & Information Website

Seal, late 1972-1977, all spoke wheels, right, rear; late 1972-1977, front, shoe brake, right side:  36-31-1-231-701.  NOTE:  this seal can be used to replace the 36-31-4-038-155 felt, and the 36-31-4-038-157 retainer, in the 1970-early 1972, but one must enlarge the seal bore on a lathe.

Felt, 1970-early 1972, front and rear:  36-31-038-155

Retainer, right only, combination seal, two parts, OIL the felt; 36-31-4-038-157

Seal, all cast wheels, front and rear, 1978 and later, pre-1985:  36-31-1-235-836.   There are many versions of this basic -836 seal, and inside the seal you may see molded-in markings of -832, -832-4, -837, etc.  These molded-in markings may well NOT conform exactly to the BMW dealer stocking part number.   Note that numbers on most anything on a BMW may well be dissimilar to the stocking part number.    MOST of these seals are interchangeable, even though some parts books may show slight dimensional changes, especially in width.   For the most part, -832 is used on cast wheels, and are interchangeable with -836, others are likely usable on all cast wheels except early 1978.

Seal, exception to the above, this is for early 1978 cast rear, where the -334 and -701 are used.

Look at the internal molded printing on your seals.

10.  NEVER EVER point a high pressure water source at your wheel seals when washing the bike.

11.  In production year 1975, BMW changed the diameter of the front axle from 14 mm to 17 mm.  It IS possible to remove bushings inside the wheel on most earlier wheels, and fit the 17 mm axle.  More on this later ....at NOTE 12-g.

12.  Swapping wheels from one year to another, one style to another, etc:
This can get quickly complicated.  BMW used several sizes of front and rear rims in snowflake, regular cast alloy, wire, and GS type external wire spoked.   I cannot list every combination or swap here.  You may have to put #1 eyeball on your proposed modification. But, here are a few ideas:

a.  A front wire wheel can be put into an early 80's airhead (that came with snowflake wheels).   Use an R80ST front wheel; or use a front hub from a R65 or R80ST and lace to a 19" rim.  You could also machine a hub from a 1975-1980 spoke wheel bike, which is narrower, as the 1975 to 1980 hub is too wide and spokes will contact the Brembo calipers.  Use R65, not R65LS, discs, or make spacers.

b.  As above, but for the rear wheel, use any 1970-1980 spoke wheel.

c.  A snowflake front wheel can be put on a very early bike, let us say a 1974 /6.  You need a 1974 R90S front end, with dual disc. This is a hassle, but can be done.  The tube spacing is different, you need the triple clamps.  You need a 1975-1980 dual disk ATE lowers, with 17 mm axle holes, and you need the 17 mm axle of course.  You CAN use the ATE calipers.

d.  /6 Airheads had a narrower fork brace (fender mount).  If needed for your metric or oversize tire size, you can use a 1977-1980 brace from a /7,  46-61-1-234-907.

e.  If converting single disc ATE to dual-disc, ATE, let us say a 1978, use the 1979 parts:  new right slider, caliper, disc.

f.  Watch out for cracking rear rims on 1974-1975 bikes, these cracks develop at the spoke hole area; the fix is to use later heat-treated rims.  TAP the spokes on the proposed 74-75 rim, and if any are quite dull sounding, there may be a hidden problem at the nipple/rim.

g.  In 1975, BMW changed to 17 mm axles on the R90S.   BMW then continued with 17 mm axles.  Swapping wheels from one year to another, can be somewhat complicated.  The 14 mm axle wheels can be modified to fit a 17 mm axle bike.  This can get more complicated if you try to swap into a much later bike, but for the /6, for example, it is not all that bad.  For the front wheel, remove the size reducing sleeve in the wheel and install the larger ID wedding band spacer (that sets the preload) used on any later model up to and including 1984.    This spacer is used on both front and rear wheels of later models.  There is a cast-in web on the old wheel that held the smaller spacer captive.  Drill it out, to a bit larger diameter than the later wedding band spacer's O.D.   To install the wheel you will need the top-hat spacers .   You may have to fiddle with things a wee bit.  Do the usual preload work before installing the wheel.

13.  ALL of the 1981 R100S polished (spokes) wheel models were recalled, at the importer level, during the time of shipment from Germany.  This was NOT a federally mandated recall.  Cast wheels were installed LATER, those  FRONT cast wheels plus all other models having cast 19 inch front wheels, up to a certain casting date, were recalled! ....see the information on this website:  https://bmwmotorcycletech.info/19inchrecall.htm

14.   Earliest snowflake rear disc brake wheels on later airheads, interference with bolts on rear drive:
I have run into this problem myself, and thought I would mention the situation, and one type of fix.   The earliest of the snowflake REAR disc brake wheels castings (these 2.75" width ones came out in 1978 on the R100S and the R100RS; and 1979 those and the RT) are not exactly the same as the later castings.  For the easiest way to identify a very early one, look at the INside of the right side dish cavity of the snowflake wheel.  If you see quite a few 'nubs' (one of which probably is stamped with the casting date) that are part of the casting, near the outer edge of the 'dish', then this wheel will NOT fit the later rear drives without modifying the wheel.  If you try to mate up the wheel, those nubs will grab onto the bolts of the later model rear drives.   The fix is to laboriously (wear respirator) use a burr grinder (or, lathe, if you have a huge one available) and remove the nubs entirely, leaving a nice smooth surface, which is important.

15.   Snowflake disc brake wheels with wider tires (not necessarily meaning an officially marked oversize tire!):
This problem was seen more on wheels before 1980 or 1981 or 1982, depending on the model.   Some tires are much wider than you might expect.  In one very egregious situation, I wanted to use a 4.00 x 18 Metzeler Enduro rear tire on a 1983 rear drive on a 1983 R100RT.  The 1983 swing arm has the fix from BMW for many wider rear tires; BUT,  that tire is so wide that it rubs the swing arm BADLY, fully inflated, and worse if deflated!  While that Enduro tire was a particularly nasty case,  many 120 ROAD tires may rub!   MOST 110 ROAD tires will not rub.    Rubbing can occur at high speeds even if not rubbing at lower speeds. The fix, for road tires, is to install the available wider top-hat spacer on the right side of the wheel. Doing so has no effect on the bearing preload.    That wider spacer is usually only needed on 1981 and earlier models, as later models have a slightly changed swing arm, not easily visible.   The wider spacer is 36-31-2-301-737.   It is 10.7 mm wide. Install with the hat INSIDE the seal.  SOME tires will let you know about tire expansion at speed, by the smell from the tire rubbing against the swing arm....or at the disc brake mount flat metal stay.     It varies with tires, wheels, etc.     Earlier mention and part number for an even wider spacer:  see NOTE 5, well above!

The drum brake rear drive has the same basic dimensions as the disc brake rear drive, and in fact it is easy to modify a drum brake rear drive to fit, although one must be careful about which rear drives are being interchanged, as some (later) have narrower shoes, earlier have wider shoes, and the wheel drum may have a narrow shoe ridge to be dealt with.

Changing or modifying the spacing at the brake stay is not complicated, as usually one can just move its point of attachment to the caliper support casting, to the outside of the attaching boss ....or, it is easy to see how to move the stay away from the tire, by moving the stay over to the left, or modifying it at its rear bonded washer, or some other means.

It is possible that the rivets on the disc could be a bit proud of the surface, and interfere with the caliper.  Simply adjust the spacing slightly, with a washer, or whatever method you prefer.  For the rivets interference, I usually make up a spacer washer, that fits between the caliper support casting and the left wheel bearing.

In one of the conversions I did, the cast disc wheel was from the late seventies, and the bike was an early eighties, both were RT's, I THINK.  In installing the earlier disc brake wheel THE initial problem (after I removed all the old wheel nubs) was how to move the wheel over to the left.   One could add a separate spacer to the right side, except that one can NOT get that spacer into the area once the wheel is on the bike!!   One could MAKE a wider top hat spacer on a lathe, I suppose or try the alternator extra wide one that I have mentioned.    Not having a lathe at my disposal at the moment, I pondered on what to do.   I decided it was not any special help to move the hat to the outside, although maybe a bit easier to attach a washer.  I decided to solder a shim ring to the top hat side of that top hat spacer, doing this very carefully and cleaning it all up to be very flat and square, and have the shim and hat side on the INside of the seal, although it certainly could be on the outside.  Having it on the inside was OK with the SEAL, and being on the inside, had less tendency to get pulled out of the seal, as the wheel was R/R, and it would not get lost, nor would it be likely to get soldering cracks.

The wheel and setup I have discussed, above, is the WORST CASE. You will be UNLIKELY to have all these minor problems, normally just changing the spacer to the -737 is enough.

16:  Re-spoking:   See Buchanan's (see URL list).  see https://bmwmotorcycletech.info/section2A.htm  if YOU want to do it.   BMW rim centers are centered with respect to the bearings.  This is only important to know if you are re-spoking.  Lots of hints and information in that link.

17:  The dual-disc front wheels can be reversed accidentally; after all, most look ALMOST exactly the same, side to side.  This can make for improper braking action until the pads re-break-in, and some other problems can be had, depending on year and model, etc.   By accepted convention, the NUTS holding the DISC CARRIER(s) are on the LEFT side of the wheel, as you sit on the bike.    Some wheels are not marked by BMW as for direction, nor some carriers (or discs).   Many folks mark a L or R on the wheel hub, or wherever.  See 18, below, for a more definitive bit of information, deeper than just 'nuts on left  side'.

18.  BMW used a JIG to machine the wheels for the valve stem hole.  The valve stem hole is LIKELY NOT CENTERED between the snowflake wheel ribs.  Typically the hole has a bias towards the leading edge of the nearest spoke, as the wheel rotates in the normal direction.  Here is how I will state this:   "The proper installation of the front snowflake wheel is, by convention, either by means of the directional arrow on the rim; or on the disc or disc carrier; or it may be noted that the valve stem (hole) is closer to the cast spoke ahead of it as the wheel rotates in the normal direction ....than the following cast spoke".