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Thread: 1976 R75/6 Wheel Bearings

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    1976 R75/6 Wheel Bearings

    I did get the front wheel bearings out and am in the process of replacing. I got the shims from Duane and, following the instructions, shimmed the bearing stack to the point where the bearings turn freely but there is no play in the axel. The thing is that I used almost .010" in shims to do it. The old (I assume factory original) set up had the bearings loaded to the point where I could feel substantial resistance when turning the axel. The old bearings showed wear consistent with too much preload (there was actually a chart on the wall in the bearing shop with pictures) Has anyone else gone through this set up and if so, is this experience typical? The rear wheel needed no shimming, it tightened up just fine and spins freely.

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    As I recall, Duane's approach is called "shake the wheel". I too bought shims from Duane a number of years ago from my R69S. Basically, you torque up the axle nut all the while push-pulling on the wheel out by the tires. If you reach torque and the "shaking" doesn't disappear, then you have too much in the way of shimming. If you are "shaking" things leading up to torque and all of the movement goes away with the very last torque, then you have the right shimming.

    Mike V. has done a lot of work with this and post his "discoveries" in this thread:

    http://www.bmwmoa.org/forum/showthre...ent-Snowflakes

    It's probably worse for the bearings to have too little pre-load than too much...they must have some and that is the whole point of Duane's method.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Front wheel went together without much fanfare. The rear wheel is another story. When I took the stack out, the "top hat" spacers were "brim" out. I decided to put them back together "brim" in as that seems to be the preferred way. I don't have a frame of reference for how far proud of the bearing seal the right side spacer stands but it seems to me that there is too much of it showing. This picture is taken with the spacer sitting against the bearing. When I did a mock assembly with the rear drive, it doesn't seem to seat all the way. To further complicate things, the left side top hat is barely clearing the seal. It is almost as though the stack is driven too far into the hub and that doesn't seem possible. Again, I would appreciate any advice from those who have been down this road already.

    Thanks
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    Mike V. #30064 30064's Avatar
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    Brim in , or brim out is a lot of times personal choice. I like the brim in or behind the seal. There's no specification for the amount of top hat production from the seal as far as I know. Only that the grease seal wipers are making full contact with the top hat. The important thing is the top hats make solid contact with the bearing's inner race when the axle is assembled and properly torqued. I think it's worth mentioning if you have different sized top hats (lt & rt), they went back in their original correct location since they act as a type of spacer also. Seal depth into the wheel hub is not a big issue either as long as the seal is at least flush with the hub bore. I normally seat the seals about 1/8" inset.

    It's hard to comment on your bearing stack installation (too far?), and preload setting without knowing the details. As long as you had the stack assembled correctly during installation - and if your hub required heating; that the heat was adequate (approx. 220 degrees F) for proper installation of the bearing stack to literally fall into the wheel hub and the right side bearing's outer race come to rest on the hub's interior shoulder. The picture you posted of the right side rear wheel looks quite normal to my eye in regards to the seal. The top-hat production in regards to the seal face looks a bit much in comparison to my '78 R100/7 all aluminum hub rear wheel, hard for me to say there's a problem. You may assemble the wheel and check the offset in relationship to the swingarm and general fitment. Don't exceed 35Ft-lb on the axle nut.

    -Mike V.
    Last edited by 30064; 05-05-2013 at 03:52 PM.
    Mike V. / San Diego
    gruntyman66 MOA#30064
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA / http://tinyurl.com/4df7hgs

  5. #5
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    Top Hat

    You might want to check the top hat installation. It looks like the inside spacer is too long.You have a spacer on each end. The one on the outside (left) is the one that is usually refered to as the "top hat" because the flange is wider than the inner spacer. It is also longer in length. So if they're reversed, then the wheel will be ofset to the left and the outside spacer won't protrude far enough through the seal.
    Boxerbruce

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    Here's what I found out and it may be useful to someone else along the way. I ordered new spacers and seals from Re-Psycle and they arrived. When I took the stack apart, the "deep" spacer came from the left side (not the drive side). The short spacer came from the drive side and that dimension is critical. It regulates the depth that the drive unit seats into the wheel hub. When I unpacked the spacers, I used the old spacer (from the left side) as a point of comparison, took the shorter (or so I thought) replacement and put that spacer / seal in first. When I went to do the other side, I found that the remaining seal was shorter still than the one I had already used. I had to take the thing apart and swap. I am assuming, based on what I read above, that I can compensate for the shorter left hand seal (shorter than the one I am replacing) by simply drifting the seal deeper into the seal cover. What I should have done was lay all the parts out, old and new, and figure out what I was going to do before I started!

    The first picture shows the drive side with the correct spacer. Subtle difference but it really shows when you install the drive unit to the wheel. The second picture shows the old drive (right) side spacer on the left and the new and old left side spacers on the right. Clearly the new spacer is shorter than the old and the way the seal was originally pressed into the seal cover, the new spacer would not span the space.

    I cannot seem to download pictures to the "reply", only to an original post. If anyone is interested in seeing the photos described above say so and I'll either post them to a new thread or, if you give me instructions, post them to this one. Thanks for the input. Chip

    I managed to delete the duplicate image but all attempts to download the replacement (one photo down from the same folder) result in an error message. The same thing has happened before and I cannot trace it to anything I am doing.
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    Last edited by cseltz; 05-06-2013 at 12:48 PM.

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    Well...it looks like the picture came through after all but the same one twice. Let's see if this works!

    Upload failed! I give up!

  8. #8
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    Quote Originally Posted by cseltz View Post
    Well...it looks like the picture came through after all but the same one twice. Let's see if this works!

    Upload failed! I give up!
    It appears you've uploaded the same picture...edit your post, go to Manage Attachments, and delete the duplicate followed by uploading the revised photo.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

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    Mike V. #30064 30064's Avatar
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    Lesson learned. Document disassembly. I always make sketches/pictures and record measurements of the left and reight top-hat spacers, seals, wedding band and even the inner and outer spacers. Also - make notes in your notebook regarding the amount of 0.05mm shims installed. These can be easily overlooked in the months and years to come or by a future owner/wrench servicing the wheels. I no longer use the 0.05mm shims but perform final preload adjustment by different sized wedding bands or by hand milling. Just a personal opinion and preference.

    Sounds like you have the problem solved.

    Attached is bearing stack assembly from my 78 R100/7 - maybe different than your /6.
    Attached Images Attached Images
    Mike V. / San Diego
    gruntyman66 MOA#30064
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA / http://tinyurl.com/4df7hgs

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    I am curious about the "hand milling" I don't see how anyone can regulate the degree of parallelism suggested while relying on finger pressure against sandpaper. I have a milling machine and can set the wedding band up on a flat table but to hold such a small object side to side and down flat would be very tricky. I was able to chuck the inside spacer from both ends in the lathe and get those flat and true but the wedding band is way to short for that. Maybe in a metric collet on the lathe?

    Also, problem is not quite solved yet. If you were able to see the second photo, you might understand the original error a bit better. The "longer" of the 2 thrust spacers is only a bit longer than the short one (about 1mm). It is considerably shorter than the original that I removed. I find that in order to get full contact between the seal and the spacer, I have to drift the seal way into the seal holder. I haven't removed the holder to see but my guess is that it may even be protruding a bit from the back. I am going to take the holder off to make sure but if it is, I think I have to go back to Re-Psycle and see if I can get a longer thrust spacer. Thanks for all the input. Chip

  11. #11
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    I've done the hand milling on the wedding ring spacers before. You use a figure-eight pattern and move the spacer in your fingers every so often. Plus you continuously measure with a good digital calipers. You can get pretty darn close that way.
    Kurt -- Forum Administrator ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  12. #12
    Mike V. #30064 30064's Avatar
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    Chip,

    I'm going to throw out a guess for your correct spacer application. If you have a quality caliper do some measuring of your original and new spacers (top-hats).

    Left spacer: 13.0mm 36311230322
    Right spacer: 9.2mm 36314038142

    The only other spacer I'm aware of is a right side spacer 10.7mm 36312301737. Maybe someone can confirm this but I believe the 10.7mm spacer is for the wider 120 rear tire fitment to give added clearance at the swingarm.

    Regarding the hand milling, I agree with Kurt. It's not difficult and can be done on a flat surface such as a piece of glass. I use a figure-8 pattern and mill in approximately 0.03mm incriments.
    Mike V. / San Diego
    gruntyman66 MOA#30064
    78 R100/7 [orig. owner] / 81 R65 [restored]
    ABC-MOA-AMA / http://tinyurl.com/4df7hgs

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    Those measurements match right up with the parts that I have and I believe they sent me the 36-31-2-301-737 for the right side in error. I am going to get that exchanged. Thanks for the advice.

    Chip

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