BMW airhead motorcycle wheel bearings

BMW Airhead Motorcycles:

Re: Airhead Wheel Bearing Clinic++, BMWMOA National Rally, July 2005
This article includes a critique of the BMWMOA-ON magazine articles of 2004.

The following article, discussion, etc., is absolutely NOT meant by me to enable you to know everything about servicing your wheel bearings.

After reading what is below, please click here for the comprehensive wheel bearing article

The purpose of this entire article is to clear up typos and potential misunderstandings, as well as to offer some of the information that I personally delivered verbally, that was NOT in the booklet/hand-out, and to offer constructive criticism for Gary's BMWMOA articles, which are VERY WELL DONE and should be KEPT by all Airheads as reference material..

Part 1 is an update for the Tapered Wheel Bearing Seminar booklet/hand-out, Airheads from 1974 to 1985 (Much is applicable to the /5 series).

Part 2 is a critique of the 4 part series on airhead wheel bearing, etc., servicing, as published in BMWMOA News in 2004, specifically, May, July, September, November.

I was involved with all of the above. For the Seminar at Spokane, WA, I was the co-leader/host (Gary L. Smith was the other); for Part 2, below, I was an advisor to Gary L. Smith.

Part 1:
FIRST....the boring corrections to the booklet/handout, some of which are very nit-picking, then some additions.

1. My name is missssspelled on the cover of the booklet/hand-out, it is FLEISCHER

2. The Booklet actually covers late 1969 when the /5 was introduced, through 1984, as in 1985 the ball bearing wheels were introduced. Very specific
      information on only the /5 is not really included, but since the hubs are so very similar to the /6, I consider the wider range of years is appropriate for the
      subtitle. It should be noted that the even prior BMW series, usually lumped under the banner of "/2"; some of which were certainly not really /2 models,
      have somewhat similar wheel construction.   Information that is useful, that I mostly agree with, if not totally, can be found on Duane Ausherman's website,
      which tends to cover the /2, /3, /5, and some /6 and /7 and later bikes:    http://w6rec.com/.

3. page 2, B., first paragraph: "space" should be 'spacer'.

4. page 3:
     top paragraph: "tighten properly" probably would be better to say "about 20 foot pounds is plenty, 25 is OK though".
     same paragraph, second to last sentence: "tight fit pressure" should be "medium light fit pressure pressure as it may tighten slightly when reinstalled"
     D, second paragraph.     Change "machined spacer" to "machined 1.5" outside diameter spacer".
     Last paragraph on this page 3: Scratch it all out, and use the following for that paragraph: ""Bob suggests the adjusting spacer should be changed or
         modified until a reading of 15 to 25 inch-ounces (or 567-943 grams) is made on the 1.5" O.D. machined spacer.   BMW recommends 21-42 inch-
         ounces, which is 794-1588 grams. YOU must decide what value range you will accept. Bob believes BMW's figures, especially near that
         42 inch-ounce high end, are too tight, and could cause bearing life to be shortened.   Bob usually tries for roughly 800 grams. For calculation
         purposes, 16 ounces is 454 grams, 1 ounce is 28 grams.   The formula is: inch-ounces divided by the radius of the machined spacer equals ounces.
      If you multiply those ounces by 28, the figure is converted to grams. NOTE that 'preload' is measured with cleaned and OILED bearings, NO
        seals, and you have to reclean and then grease them when the preload is done.   The seal and grease are variables, so if you decide to do preload
        "testing", to see if in the ballpark, WITH 'as-found' grease and seals, be cautious, as those will tend to RAISE, not lower, the readings, so you
         do not want readings below specification during this sort of a test.

5. page 18: This is a subjective 'feel' test, and the reference is to photo #048.   I like to use the machined-spacer and string gauge method for a final
        check, with the hub assembled and axle in place and axle fully tightened.

6. page 30: In item D. change .."...rotor is..."... to: ...."....rotor style wheel is...." in item 4., change "Knirled Nuts" to "Round Nut"

7. page 32, item 5, change "pinwrenches" in the LAST sentence, to the singular: "pinwrench"

8. page 34, the last paragraph under item 12 has a mizzzspelling: change "rubble" to "rubber"

9. page 40, item 10, "axel" should be "axle"

10. page 46, item 3, "(119)" should be "(125)"

11. page 48: Item 4 is possibly confusing. You do NOT really have to do any converting, you are, after all, just comparing one reading to another
reading on the same micrometer.
On item 5, place a note: "see picture #128".

12. On page 49, add some sort of note to picture 128, something like this: "Do NOT sand the surface of the part with the method illustrated. Use the
        part on a piece of very fine grit sandpaper or silicon carbide paper, upside down on a surface plate, which can be a real machinists type of surface
        plate, or a piece of plate glass, etc., doing figure eights with smooth moderately light downward pressure, squarely as you can, and rotating 1/4th
        turn after each 'eight'. OR, do it on an oilstone. Holding as shown will put an angle on the part which you do NOT want to do. Experience has
       shown that somewhat polished ends on all spacer parts make for more predictable and repeatable preload. Do NOT fail to clean the part of gritty
        particles."

General notes, print and save:

1. If replacing bearings on any pre-1985 airhead, it is accepted good practice to have things clean enough to eat off of, and no residues or grunge, NO
     protruding metal marks from hamfisted tools use, ETC., so that the parts all go back together completely and fully.   On the pressed-in-place hubs,
     the outer bearing race MUST fit FULLY BOTTOMED into a CLEAN to the very corner edges cavity. On the heated assemblies, the outer races
     and inner spacer (especially the large diameter one) MUST be assembled tightly, to avoid any even slight clearance between these two races and inner
     spacer.   That is why the tighten axle assembly method is used. A 0.001" error will make for a noticeable change in preload; and it is possible for the
     preload to change after assembly, so you do NOT want that happening, so assemble per instructions.

2. The wheel bearings are a common generic number 30203, you may see letters on them, and/or a prefix. You might see something like:
FAG30203A.M.P....many variations. FYI, these are also used at the swing arms.

3. The spacers I call "top-hat" types, since that is very common and very descriptive, can be installed in the wheel as installed on your airhead, so the HAT
      is on the outside or inside of the pressed-in-place wheel seal. Very early models will probably have them OUTside.   These external-to-the-hub spacers
      do nothing special (they are certainly NOT part of the preload control); but, take up room to allow the wheel to fit between the fork lowers, or rear swing
      arms, and a major purpose of them is to ensure a good weather sealing for the bearing, in combination with the seal.   I prefer top-hat spacers on the
     INside of the later hubs, which means that you have to install them (OIL them for ease in pushing into the seal material) them into the wheel seal BEFORE
     the seal is installed into the wheel cavity.   The seal and spacer are installed together, usually just using a proper size socket (not quite full diameter as the
     seal outer).   I have some reasons, and just one uncommonly known reason is that some seals have the outer lip angled OUTward, and could be slightly
    distorted if the hat was against it, but might be spaced away too. The seals are the only protection for the bearing from water damage.

4. The Booklet does NOT give any of the history, background, and how the environment and mileage, and exactly how lack of grease or old hardened
     grease, or other things, affect the bearings. NOR does the Booklet explain that the original design was way over-kill as BMW INTENDED for their
     bikes to handle the high sideways forces from sidecar use. Many of these things were explained, verbally, at the Seminar....in the History, Advantages,
     Design, Environmental Effects, Safety, Economics, Car Wand Washers....etc....part of the beginning of the Seminar.   NOTE!!!.... BMW sometimes
     ships even brand-new wheels IMPROPERLY greased and IMPROPERLY preloaded. NEVER 'assume'. Some Dealerships have been guilty of not
     servicing brand new wheels before sale of the wheel to the customer.

5. There was a goodly amount of discussion at the Seminar about the design. The original design of the early wheel hubs enabled crude, no special tools
      methods of servicing; that is, no 'pullers', etc., were needed.   I explained in some depth that the early wheels had a removable INNER cylinder spacer,
     that set the distance between OUTER bearing races, and still had the wedding band spacer that set the INNER spacing. Thus, on the early hubs, there
     were TWO methods of setting spacing, and the large diameter spacer inside the hub CAN be end-sanded slightly, if required, in a situation wherein you
     do not have the required wedding-ring.   Of course, sanding the large diameter spacer brings the bearing outers closer together, which has the same
     effect as having a WIDER wedding ring band spacer.

6. If you remove an inner bearing (that means the part with the rollers) for normal service work, be sure to mark it with an engraving tool, mark them L for
Left, R for Right. That is because you do NOT want to mix up the bearings. Mark it on an end face.

7. There is a modification, easy to do on any grinding wheel, for the early hubs, so, afterwards, there is no need to heat the hubs again, for
     normal cleaning and lubrication. Very worthwhile. This involves grinding the spacer tube 'flanges' just enough plus a tad, so that tube will
     remove from the left side without removing the left outer bearing race (for the future).   Greasing of the inner, still captive bearing, can
    still be done by properly using Ed Korns round tool with the zerk fitting on one end.

8. Some more verbal things from the Seminar:
    a. Shallow steel inserts, versus deep steel inserts on cast wheels.
    b. Single sided rear ends, that is, Monolever and Paralever, eliminated the tapered wheel bearings servicing entirely, in favor of the INternal large bearing
          inside the rear drive...with their own set of problems over much mileage.
    c. The R65LS front wheel introduced the 'Sealed Ball Bearing" design in 1981, far before the 1985 introduction on the larger engine models.   That R65LS
          had an odd-size, it was 17 x 40 x 12, BMW # 36-31-1-242-854
    d. 1970 and later heated-hubs bearing assemblies are disassembled and assembled to the wheel, from the left.
    e. FRONT all-aluminum hubs are heated for outer race removal.
    f. SOME very early /5 wheels had bores on the RIGHT side that were smaller, and used a smaller grease seal, and the top hat spacer remains captive.
    g. A FEW early cast wheels WERE all-aluminum, that is, there was NO cast-in steel insert (where the outer race is pressed-in as on later models).
       MOST cast wheels have these steel inserts.  Those few early wheels had to be heated. Don't be confused here...."Steel Insert" as used here is NOT
         the outer race, but a cast-into-the hub part. SOMEtime during 1978 production of the snowflake wheels, they were changed. The FRONT wheel
         had the cast into the wheel steel insert, the REAR DISC brake wheel ALSO did; thus those two have outer races PRESSED-OUT and
         PRESSED-IN. Heating does not injure the wheels that normally use room temperature pressing (there is no purpose in heating them, of course), but
         heat is MANDATORY on wheels requiring it (all aluminum, no steel insert cast into the wheel). 1979 to 1984 wheels were all the pressed-type, for
         these outer races. A magnet can be used, sometimes, if not touching the outer bearing race. You can refer to AIRMAIL of August 1978 and June 2001.
    h. The first 17 mm front axle was 1975, and earlier can be converted, and the larger axle does not bend easily.
    i.   Do not reverse a dual front disc wheel, or you may have brake-pads break-in to do again.....and may have to adjust the ATE swinging calipers, if you
         have those types. By conventional practice, the NUTS are on the LEFT side of the motorcycle front wheel for a disc brake wheel. NOTE: some get
         confused by left and right. On ALL vehicles, left-right means as you sit normally on/in the vehicle, unless the notation specifically says something else.
    j. NEVER EVER rest a disc brake wheel on its disc when working on tire changes, etc.   You have a great chance of permanently bending the disc/carrier,
        and then having lousy surging brakes.
    k.  19" FRONT snowflake wheels were recalled if the casting is stamp-marked BEFORE 10/82. See my website article. That IS a hyperlink.
    l. The wedding band spacers, officially called spacer shims, are approximately 1/4 inch wide for 17 mm axles, and approximately 3/8 inch wide for the
        earlier 14 mm axles. You do NOT need a big bunch of these, maybe none, maybe use Duane Ausherman's convenient shim kit.
    m. Ed Korn's greasing tool can be used, with some care in inserting (to several slight depth changes during use).   Years ago, there was another type
          of greasing tool made by Chuck Walus, it was described on pages 23 and 24 of the June 1978 issue of BMW Owners News. I have one.   You
          can also use a common cone-type of bearing greaser, for the bearings once OUT of the hubs, although hand greasing is OK, if you are thorough.
        Re-greasing cleans the old, often contaminated and hardened grease out, and puts nice new fresh soft grease into the bearing.   Don't be afraid to
          use lots of grease.
    n. I use two special spacers during my preload work on wheels.   The machined steel spacers that I personally made for 1979-1984 RS and RT models
        were 1.5" diameter; 0.668" +.002, -.000 center bore. Of the two spacers, one was 2-1/8" to 2-1/4 inches long (unimportant, just in that range); the
        other was 2-3/4 to 3 inches long. One could also use 2.0 inch diameter material (or, any other diameter that FIT properly), then you must use the
        formula to calculate the proper ounces or grams for YOUR spacer diameter.   The ENDS must be flat and square to the bore, which is why they were
        made on a lathe; AND, they MUST fit the bearing and not press on the hub. If you have some made, determine the length YOU need first, and have
        your cleaned and lubed axle handy to check for a smooth slip fit.   Some folks reading this may wonder about the use of the common 'pipe' as spacers
        in part of the procedures in the booklet, especially for the heated hubs assemblies. That has been found to work OK if done as described. Not quite
        as nice as these special steel spacers I had made up, which are much more repeatable in results. If using common pipe material, have the ends squared
        and smooth, done on a lathe. It is quite important that the spacers you make up, fit very squarely to the wheel bearings.   Those two machined spacers
        allowed servicing the preload on the front AND rear snowflake wheels, which is why I selected the particular lengths. YMMV.

Part 2: This part applies to the articles in MOA-ON in 2004:
1. May 2004, article on "R90/6 Front Wheel Hubs"; this was PART 1 of the 4 Part series of articles. This article has a lot of pertinence to all the airhead
     pre-1985 wheels. Page 26, top illustration, the upper parts are for the 14 mm axle, lower parts for 17 mm axle. Page 28, photo #14: 1970-1977 spoke
    wheel, rear, left; 1970-1977 spoke wheel, drum, front, left, and 1974-1977 all spoke, disc, front, left AND right.
2. I make no comments on the July 2004 MOA-ON issue, which had Part 2.
3. September 2004, was Part 3.  The first page, 28, has a photo of Ed Korn's greasing tool, one of my types of steel spacers, etc. This article has a hub
     machined out of a snowflake, showing the simple string pull-scale test, and shows some information on the older hub style parts, etc.   Photo #44 was
     updated in photo 17 of Part 4....the seal and spacers, not shown, must be in place. In all these 4 articles, much is seen in the Seminar Booklet, and
     vice-versa.
4. Final Part 4 is in the November 2004 issue. This is the Summary article.   There is also a chart for many of the wedding band spacers and part numbers.
   In item 7, it is NOT SO that the wheel seals need to be out for the Shake test; nor do you want the axle nut loosened. Some of this item 7, which is
     lengthy, need modification or interpretation, but when doing the job you will see what I mean, nothing serious. I thought about re-writing it, and then
     decided it was not at all needed.

Addendum #1: NOTE!   String scales are not common hardware store items.   I have some precision types in my shop, but those are hardly
     needed for this purpose (I do have two of the inexpensive 8014-MA, below). At the Seminar, I had purchased with my own funds, about a dozen of
     two types, to pass out to 'door prize winners', all made by Ohaus, one was type 8004-MA, which is a rectangular type, has an adjustable zero, and
     reads in both grams and ounces. They also have a round type available as part 8014-MA. These are fairly cheap items, a FEW dollars.   EITHER
     one is QUITE adequate for the preload purpose. I purchased them from Sargent-Welch, off the Internet: http://www.sargentwelch.com/
     Sargent Welch WLS3774-F, Ohaus 8014-MA, dial type; Sargent Welch WLS3678-DD, Ohas 8004-MA, rectangular type.

ADDENDUM #2: Read this article!: http://w6rec.com/duane/bmw/wheel_bearing/index.htm

Revisions:
01/23/2010: minor cleanup
05/22/2010: Clean up some more.
04/19/2011: Add Addendum #2