Section 3:  Catch-all Section
© Copyright, 2012, R. Fleischer

catch.htm
article 54, section 3

Be Sure to read Article 54, subsection 5 on tires and subsection 2, and there are numerous sections in main article number 54, that expand on things.

Note:  While the information on this personal website for BMW motorcycles is more up to date, you may want to review the article entitled Wheel Bearings, as posted at: http://www.airheads.org, a website devoted to BMW Airhead motorcycles.    See the left side of the main page, and click on Technical Tips.  That article has, in places, a different slant and way of describing certain items, and is well worth reading.  

 See also:  http://w6rec.com/    Hunt that website for the wheel bearing article, and READ IT ALL. 

NOTE 1:  Early wheels, such as 1970-1978 (except 1978 rear DISC snowflake wheels) have 100% aluminum hubs (no cast-in steel insert) which MUST be heated to remove and replace a race (and center assembly).  Later wheels have cold-pressed-in races.  Doing it wrong is not a problem with the later wheels, as heating does nothing terribly important, but pressing out, cold,  the early style that are supposed to be heated, WILL injure the wheel hub.   It is also not a great idea to do a large number of heat and R/R cycles on the all-alloy hubs.  

Note 2:  Some modifications to some early hub parts (especially /5) can eliminate R/R of the outer race for normal cleaning and greasing, etc.

NOTE 3:  HINT!  For the early all-aluminum hub (withOUT steel insert) wheels, FREEZE the outer race, ETC., before replacing it into the heated hub...this is done as an assembly.

Note 4:   NOTE!!  The 1978 REAR DRUM snowflake is an odd-ball, this can be identified by it being a snowflake, rear, drum, and 5 bolts holding the seal retainer.  It has a NON-insert hub, and must be heated for servicing the bearings, and is a POOR DESIGN.  If the outer race has spun in the wheel, you may, or may not, be able to salvage the wheel.  You can ask me personally for advice.

NOTE 5: >>>  BESIDES the method using the spacers you would have to have machined (see the airheads.org article AND this one), there is a common method of checking preload, with the wheel on the bike, seals in, ready for riding, except that the wheel is off the ground, and the axle nut  loosened (and loosen the clamp if it is a front wheel) and then slowly tightened while feeling the wheel bearing play.  Actually, this can be done without the wheel off the ground if one is careful.  This 'feel' method works fine, but takes some experience in knowing what the proper 'feel' is.  The wheel is generally wiggled with hands at 9 and 3 O'clock.  Just barely no detectable play is correct.  Without experience, you can be way off doing this.  If normal axle nut tightness reduces that play to noticeably no play and too much 'then some'....and even MAYBE tight beyond that, you need to do preload spacer work.
This really is a bit tricky.

NOTE 6:  (and see NOTE 23 below and other notes in this article you are reading).....BMW rims that were designed for tube use should NOT really be used without the tube.  The rim shape is the industry designated WM2.  While the valve stem hole could be enlarged and a small car-type tubeless type valve installed, and then a tubeless tire withOUT a tube installed, it is YOUR choice whether to do this. BMW also, as well as other manufacturer's, sell various short, long, and difference width, metal stems that have an inside sealing ring.  The BMW part number that would fit a snowflake wheel without enlarging the hole (internal spot facing a good idea)  is 36-32-1-452-748.   It HAS been done by many folks, successfully, even on the racetrack.    However, there is a safety concern if you run into something such as a good sized rock or a goodly sized pothole, as you might then have a rim bending that caused catastrophic deflation, and maybe the tire come off the rim.  While that does not happen very often, it is possible.  The more common nail puncture is the type that concerns those who really hate repairing tube type tires, and it is those folks that typically think about going to a tubeless conversion.    BTW, an EXternal type of tubeless tire plug is an emergency repair...do NOT drive far, nor fast, until the tire is properly repaired with an INternal plug and patch cover, if the damage allows.    Even with that type of repair, it may take a tire expert to look at the tire and see if it is usable.  In some respects, tubeless tires, especially with steel cords, can be UNreliable after a repair, and those cords might cut the plug.  One must ride cautiously, and NOT at high speeds, on a repaired tubeless tire, in many situations.

Here are some ideas to also consider about tire repairs...and...be sure to go to my  tools.htm page and read about tire tools!

   Have a Credit card and Cell Phone.....and a tire repair card from God... that you will not have a flat tire on Saturday evening...or Sunday or Monday, when the bike shops are closed. Seriously though (and a credit card and phone are not a bad idea, some have only that), you probably need to know how to repair a tire/flat.  I could write an entire article on that, including information on the cute and cheap compressors of electrical and cylinder types.   Chitech had a nice booklet on fixing tires....using the same 1979 R100T bike as a demo as Oak still rides..it was his that modeled for the booklet.....:-).   
Basics for tube repairs is two short and one long BMW tire iron (all fit the tray), compressor of one or the other sort (I do NOT trust carrying enough CO2 cartridges.....); tools that will allow the wheel to be removed.   Center stand can sometimes be used to break the bead, but a real bead breaker is better, you can make one from a C-clamp, or purchase one...I've seen two types that can be taken on a m/c.    You need a fresh tube repair kit. ....patches, glue, roughing metal piece.  Be sure that kit contains a type of tire cap that unscrews the valves....better to have that type ON the tubes on the wheels, where you know they should not get lost.   You need two 8 ounce, plastic bottles with a flip-spouts......the type used for hair lotions and so on.  Fill one with REAL tire talc.  Fill the other with properly diluted tire lubricant.   You can use a HUGE tube of K-Y or other 'personal' jelly.  NOT Vaseline.  I do NOT really like using SOAP...some soap is very caustic, and may damage rims.

 Motorcycle tires do not have the same type of loads on them as car tires, although some high power motorcycles can really put a lot of torque on the rear tire at take-off.   For CARS, excessive amount of tire lubricant has been, on occasion, cause for the tire to spin on the rim.   For motorcycles, this movement of the tire regarding the rim, is very seldom seen in normal riding from horsepower effects, and can pretty much be disregarded.   I know of NO problems with using excessive tire lubricant on motorcycles for street use.  Carry a spare REAR tube.  Carry TWO of the THICK BLACK RUBBER, hooked ends, stretch cords (bungees).  

Getting a rear wheel out (1970 and later models):
    (a).  Bike on center-stand on steep curb (seldom available....so....got to step b).
    (b).  Bike on center-stand. Tie center-stand to front exhaust crossover pipe. SECURELY.  THAT is what the extra strong bungees are for.
    (c)   Remove front wheel. You will have to undo the disc brake calipers, hang them via a bungy, NOT by the hoses.  You may have to remove the drum brake unit.  
    (d)   Put gloves on ground.  Slowly tilt bike forward, so forks rest on the gloves.
    (e)  You now have the rear end of the bike WAY up in the air, and PLENTY of room to work.   Single sided rear end bikes have it easier, but you still have to ensure that you can remove and replace the wheel.  Usually it is, however, a
             tubeless tire...and can be repaired temporarily with EXternal plugs.  An internal plug and patch on the inside of the tire is the proper repair.  You are not really suppose to ride at any speed with an external plug.  Some insert tubes. 
            Your choice.   Keep in mind previous cautions on steel cords cutting inside or outside plugs, over time/miles.

For serious work, such as repairing a tube, or installing an INternal patch/plug, breaking the bead is NOT fun.  You must have the tire totally deflated.   You can try the weight on one side of the center-stand; side-stand; I prefer a tire bead breaker.

With tubes (and see NOTE 23, below), the purpose of the stem nut is to help in installing the new tube!  After installing the new tube and inflating the tube/tire (making sure the stem is sticking out at 90°), the nut can be thrown into the junk box, or thrown away, or moved up against the cap.  Frankly, I never throw anything away.  Just do NOT have it down against the rim.  If it is against the rim, and if the tire should shift on the rim during a serious flat situation, the tire could try to rotate the tube...and having the nut at the rim does not allow for ANY tube movement.     Some folks have modified the 8 mm hole in the snowflake tube type rims, to 11.5 mm, and modified the inside area too, so that larger tubeless stems can be fitted to tubeless tires without running tubes.  Earlier in this article I gave information on stems that do not need the hole enlarged, but spot facing is a good idea, and may be needed anyway.   Be advised that if you have such a hole size conversion, and then revert to TUBES, do NOT use RUBBER to seal the inside, use a metal washer, shaped properly.  Use of rubber could cause the tube to not eliminate trapped air between the tube and tire, causing chaffing of the tube.     SOME folks have cut off a 'rubber doughnut' by modifying an old car-type tubeless rubber stem.  They then use the rubber piece to seal the m/c tube at the rim, with a washer, and nut.  This works, but keep in mind all caveats.  Ultimately, anything done besides the original stock method means you are on your own, safety-wise and performance-wise.

NOTE 7:  (and see later NOTES here)....The factory recommended tire pressures for your early airhead....certainly prior to the mid-1980's...is possibly too low, and a good beginning pressure is the tire manufacturer's published recommendation, if higher.  You will probably find that the appropriate pressures are LOW-thirties for the front and higher thirties to even the sidewall limits (42?) for the rear.  There is an old rule of thumb, still works well, that says that the tire pressure should increase about 10% from cold check to being checked after a nice longish ride.    The rule says that if the pressure does not increase that much, to lower the cold pressure, and vice-versa, of course.  That rule works out quite well sometimes, but NOT always.   The tire pressure needed varies with the loading (are you heavy?  two-up?), and speed you might travel at.   For the CLASSIC BMW airhead ride, use the stock sized tires, in the old ribbed designs....with the original manual-stated (or under the seat label) pressures.

NOTE 8:  REAL tire talc (no oils in it) and REAL tire vegetable based lubricant (thin it per instructions) are available from tire distributors and other places.  You might want to obtain some 6 or 8+ ounce  flip-tip plastic bottles like used for certain hair and other products, and have some talc in one, some thinned tire lubricant in the other, and keep them on your bike with your big C-clamp or whatever you use to break the bead from the rim.  I keep a spark plug hole type of compressor adapter, patches, spare rear tube (front one too on LONG tours) on the bike.   Some may want to use the guts, modified slightly, of one of those cheap CHEAP 12 volt compressors sold at WalMart, etc.   They DO work just fine.  Frankly, I LOVE those modified compressors...commercial versions are available from bike shops, etc.

NOTE 9:  ALWAYS replace tubes when replacing tires.  SOME say to never patch a tube, only use new tubes.  I have done both, but replacing a tube anytime the tire is demounted is probably the safest thing to do.    The best tubes are natural rubber based, and these resist long tears/rips better, but they also leak, although very slowly.  Another good reason to keep an accurate tire pressure gauge in your tankbag, or wherever on the bike.   I recommend against the super-thick competition tubes.

NOTE 10:  Almost all tires marked as TUBELESS are actually OK to use with tubes.  If not sure, ask your tire distributor.  Then, again, many motorcycle places that sell tires know almost nothing about the finer details.    This generality about tubeless usage is probably NOT true for radial tires.  I don't recommend radials for airheads anyway.    NOTE that tires containing tubes are speed limited...to less than the tire rating itself.  The rule of thumb is to reduce the speed rating by one.   While on the subject of tire ratings:  It is not commonly known that H rated tires MAY last longer at reasonable speeds and loads, as compared to V and higher rated tires.   This is especially so with the same make and model.  Sometimes this is purely the result of the lower rated tire having DEEPER tread!  Deeper tread squirms more, and generates more heat, so for higher speed rated tires, manufacturer's may well reduce the depth of the tread.  So you MIGHT have the situation of purchasing a high speed rated tire for whatever reason (not speed!), and find out it costs more and lasts less!  Note also that larger tires will change the handling of your bike, you may or may not like the difference.   You may or may not even notice the difference!  In some cases a larger front tire in a fast handling type, the Metzeler ME33 is an example here, will revert to more stock-like handling, but last longer, and handle better when pushed hard, than the smaller size.  Some early front fender braces do not allow for wider tires.  For the rear tire, increasing the size may well help with load carrying ability of the bike, but going too far may cause the rear end to change the front end handling too much for your liking.   BMW has shipped tire rims with rim widths from 1.85 to 2.75 inches for the tube-type airheads.  Some tires are too wide for fitting, safely, to those rims, and the tire might have a rolling tendency in hard cornering.    AND, as mentioned, the larger tire may not fit such as the front fender support or the rear swing arm.

On the old airheads, generally 110 rear tire will fit, 120 may or may not, and the same for 100 on the front.

 For those that do not understand some of this handling chit chat easily, picture your bike with a 3 foot wide rear tire, trying to turn, downhill sweeper.  OR, consider that the wider the rear tire the less the front and rear patches line up in a turn.  

GENERALLY speaking, front tires of 90 or 100 section or 3.25 or 3.50 are quite usable with rear tires of 4.00, 110 and even 120 section, on all the earlier airheads that used 3.25 front and 4.00 rear.  SOME 120 tires are too wide to fit without rubbing.  Often the rubbing occurs only at high speeds.    The 10.7 mm wide spacer (stock is 9.2 mm) used at the right side of the rear wheel, part number 36-31-2-301-737, is usually not needed on 1981 and later twin shock models, when using the oversize 120-90 x 18 oversize rear tire; but SOME DO REQUIRE IT.    The 110-90 x 18 rear tire fits most airheads easily.    Frankly, unless you have real reasons, such as very high loads, the 110 size tire is likely the way to go.    The 120 tire (and often any rear tire) usually must be fully deflated, and messed with, to remove or replace over the brake drum rear ends, and is still fun with the disc brake rear ends, even though the caliper can be moved out of the way.   It can be helpful to cut the rear fender sides on a smooth curving angle, from the license plate area up and forward, to help tire removal.  Those with /2 bikes with hinged rear fender may stop snickering.   Final note here on tire sizes:   As noted, some stock front fender braces may not allow you to fit a large front tire, but the brace can be changed to the later version to allow it.  NOTE!....the classic BMW handling is had ONLY with the exact original size and style of  tires.
 NOTE:  BMW uses 'top hat spacers' at various places in the bikes.  You are likely to find them at the swing arm sides, and the wheels.     One top hat spacer under 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.    Why no one but me seems to know about this spacer has had me wondering..

NOTE 11:  Removal and replacement of tires is VASTLY easier if the old and new items are placed in hot sunlight and allowed to heat up considerably.   It is very helpful to have THREE tire irons, two can be the standard BMW, and one should be the longer BMW one.  Tire lubricant is a MUST.   Do NOT pry on wheels with the discs laying on the ground...discs must NOT have pressure placed sideways on them.  Gasoline is NOT an appropriate tire lubricant, and neither is common soap.

NOTE 12:  Whether or not tire balancing is any big help, meaning worth doing, is debatable.  It certainly is worth the effort and cost if the assembled wheel/tire is quite far out of balance.   Those who do a lot of miles and do their own tire work may want to invest in a tire balancer.   Some no-cost one's can be built, and one of many such types is described on the airheads.org website,  but something like the Telefix is worth the money.  The tire balance mark, usually a color dot, goes next to the valve stem.    If two dots, usually the red is the balance point.   There is 3 hole and 4 hole adaptors available for the Telefix for the single rear shock airheads. 

NOTE 13:  Tires MUST be mounted concentrically.  Tires are manufactured with a concentric ridge line near the bead, so you can easily see if there is equal spacing all around, using the rim edge as a guide versus that concentric tire ridge line.   It is a PIA to have to demount the tire if it is not concentric and the most common cause for that is failure to use a lot of proper tire lubricant during assembly.    Wet the lubricant or add more if it starts to dry out.  When you are done, wash the tire.  A new tire should be VERY thoroughly washed with common soap or dish detergent mixture, and hosed off really well.  I use a fairly stiff brush.  NEVER ride hard, especially in cornering, on a brand new tire, rather, allow 50 miles or so.

NOTE!!!...Controversy exists over how dangerous brand-new tires are, right from the manufacturer.  The truth is that the tires may be VERY slippery.  How to best handle that is, of course, to ride gingerly at first, but I have a good suggestion, that REALLY works!   FIRST, be sure to wash the tire with hot water containing dish detergent.  THEN, after the tire dries, rough up the tire tread with a STEEL brush of the type that painters use...get at any hardware store or lumber supply store.   You really need to scuff up the tire tread, and it can take 15 minutes or so to do properly.  This will almost entirely eliminate any trace of slipperiness.

NOTE 14:  It was not all that long ago that tire manufacturer's generally did not want you using over perhaps 50 psi to seat the bead.  Most will now say a maximum of 50% over the maximum pressure molded into the sidewall.  Even with lots of tire lubricant, I never go over 60 psi.   Going higher than 60 is QUITE dangerous, so be careful, and use safety equipment, and don't go over 60 psi!   Use LOTS of tire lubricant on the tire bead, that must be on a CLEANED rim.  Many a time the tire will continue to move slowly upon the rim, seating itself concentrically, after several minutes of sitting there in the sun, well-lubed, so be patient, and ..again...the use of proper wet tire lube is a BIG help (flow the stuff onto the bead during the initial assembly AND during the inflationing).    Rarely one must demount and remount a tire.  I almost never do that, since I follow my own advice, see below  "HINT/SECRET!:"

 TUBE tires:  Once the tire is fully inflated, and the ridge lines look concentric on both sides of the rim, & the tire is fully seated at the bead of course, it is a good idea on tube-containing tires to THEN fully deflate the tire (it will not come off the bead-rim), bounce it a bit (upright, turning it and bouncing a few times in different spots), and then reinflate it to NORMAL pressure.  That is just ONE of the reasons you got your hands full of tire talc and rubbed it all over the tube outer surface and the inside of the tire.   Bouncing, deflated, will tend to let any tube irregularities inside smooth out, and then you can refill with compressed air.

  HINT/SECRET:  Many a person has tried to get a tire, properly located in the middle of the rim, to fully seat to the rim and EVENLY all around during inflation without success, even after lots of real tire lubricant, and even with the tire sitting in the sun.  A REAL secret is to do two more things, right off the bat.  First, the compressor must have a substantial tank, 5 gallons being fine, 3 might be OK...........and it should be filled to 100 to 125 psi, or whatever your compressor can do over 100/125.  Secondly, it is critical that the air chuck NOT HAVE THE CENTER PIN...you need to remove it!   That allows a FAST flow of air from the chuck.  The second thing to do that is even more important to ensure a FAST flow of air, is to REMOVE THE TIRE/TUBE VALVE CORE.   Doing these things with a well-lubricated tire, will ensure the tire snaps into full concentricity NICELY!  You will have to hold the pin-less chuck against the tire stem while you open the valve on the compressor, or otherwise turn on the air.  It is the SPEED at which you inflate that is so important (assuming a lubricated hot tire).

NOTE 15:  Airheads CAN use the spark-plug hole type of air compressor.  Any possible influx of gas mixture from the carburetor is quite minimal, as these devices use an intake port in the adapter itself.   However, since ANY gasoline vapor will rot rubber, at your earliest convenience deflate fully and re-inflate using fresh air.  You might have problems inflating with any air source other than a shop compressor, see item 14 above.  But, you will have a good shot at it with any air source.

NOTE 16:   For the rear wheels on twin-shock models, and all pre-1985 front wheels, wheel seals are damaged during normal removal for servicing of bearings for greasing, preload work, etc.  DON'T even think about trying to reuse a seal!!   Keep a few new wheel seals on hand.  Greasable bearings (pre-1985) should be re-greased at each tire change, and the preload should be checked every few tire changes.  Any modern thin feeling NON-FIBROUS grease is likely OK.   I suggest you select one specified for disk brake wheel bearings if you are not sure about the grease characteristics.  Modern greases have high melting-flowing temperature characteristics, and high resistance to water wash-out.  Use of these modern 'thin' greases CAN allow for fairly close preload adjustment withOUT the need for cleaning, oiling, checking preload, then cleaning again and greasing.  BUT, some experience in this regard is a good idea.  Chevron UltraDuty EP in NLG1 or NLG2, BMW Red #10, etc. 

NOTE 17:  In 1985, BMW began using non-regreasable sealed ball bearing units.   These are totally different from the discussion herein on preload, and these discussions of preload methods do NOT apply.   Those bearing units are NOT serviceable.   There is an exception to that 1985 date.   The R65LS was manufactured from January 1981 to October 1985, and its FRONT wheel uses a 36-31-1-242-854 BALL bearing that is sized 17 x 40 x 12....the same size as the taper bearings.

NOTE 18:  The original BMW wheel weights of the snap-in-place type are still available, as are the clips to hold them to the rim.   I prefer these to the glue-on/adhesive types, but the preference is not an overwhelming one.  Only certain sizes are still available, and this information is, of course, subject to change.

36-31-1-235-625   5 gram

                    -626   10 gram

                    -627   20 gram

                    -628   30 gram

             -240-152   15 gram

                    -153   25 gram

36-11-2-227-943:  5 & 10 gram segments on a strip, self-stick.  Originally were for R1200C.  Work fine on others.

The clip is 36-31-1-235-632

NOTE 19:  NEVER EVER work on a wheel...especially with tire irons, with a disc lying on the ground.  Support the wheel (tire actually) on 2 x 4's, or use a lidless old oil or grease drum, etc.   Repeating a prior caution here, NEVER hang the disc brake calipers by their rubber hoses.

NOTE 20:  The wheel bearing seals, etc., are a bit complicated, and you should also be aware that some parts are interchangeable, and some are just updated versions, and that variations exist between drum and disc brake models, and even between left and right parts on the same wheels...in a few instances.  

***Part numbers get superceded all the time.  Your dealer has the latest numbers.

Seal, 1970-1977, spoke wheels, rear, left; 1970-1977 spoke wheels, drum brake, front, left;  1974-1977 spoke wheels, disc brake, front, left and right:   36-31-1-230-334.  NOTE:  Left sides same early and late /5, and very early 1978 cast wheels rears.  

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 
    NOTE:  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.  

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

NOTE 21:  Brand-new tires need to be cleaned as mentioned earlier herein, AND need to be run 50 or more miles to break them in.  Do NOT try tight pushy turns and very high speeds until the tires ARE broken-in. Ride with increasingly larger angles.  However, if properly washed....and roughed up with a steel brush...they are moreimmediately usable...if done properly.  Another way of breaking-in brand-new tires...or at least speeding the process....is to scrub them, including the depth of the tread, sidewalls, etc., with an old-fashioned bristle-type floor scrubbing brush, using hot water and detergent, then rinse off.   NOTE!....no matter how you try to speed up the breaking-in process, the tire will need some riding to warm up the tread and properly scrub-in and treat the rubber from the heat generated at the surface contact.

NOTE 22:  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 earlier wheels, and fit the 17 mm.

****Many a time someone wants to swap wheels from one year to another, one style to another.    This can get VERY complicated.  BMW used several sizes of front and rear rims in snowflake, regular cast alloy, wire, and GS type external wire.   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.  Early airheads had a narrower fork brace (fender mount).  If needed for your tire size, you can use a 1977-1980 brace from a /7.  Or,
         buy one:  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.
    d.  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.
    e.  Early snowflake rear disc brake wheels on later airheads:  see #26, below.   see also #27, below
    f.   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 a tad 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.

NOTE 23:  Be aware of the following:
Failure to have a valve CAP on the valve stem CAN cause you to loose air at VERY high speeds, as centripetal force allows the center part to release air (the spring might not be strong enough to prevent that). 

NOTE 25:   ALL of the 1981 R100S polished (spokes) wheel models were recalled, during the time of shipment from Germany.  This was NOT a federally mandated recall, and the bikes were returned to the various distributors with cast wheels.  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:  19 inch recall

Revisions: 

03/07/2006:  all prior updates, plus add #29, plus make quite a few changes in the entire article, bringing it up-to-date.
01/06/2008:  remove hyperlink for agwalker.com as it is dead.
08/19/2009:  minor updates
12/05/2009:  add R1200C type 5/10 gram weight strips p/no.
02/25/2010:  minor clarifications
05/22/2011:  expand #14, in line with my other articles.
09/20/2011:  Edit #10, adding information that was already in Section6.htm, on the extra-wide spacer
 

© Copyright, 2012, R. Fleischer

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