wheel bearings

Discussion in 'Airheads' started by mooch, Feb 10, 2021.

  1. mooch

    mooch Adventurer Supporter

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    Ok, I have a 78 R100S which I am finally going over to make reliable and fun. I bought from original owner when he stopped riding. Has at most 20k miles on it. I am starting from the rear and working forward. Not going to "restore" it. I was going to repack or replace the wheel bearings on the rear while I had it off and then began to read about correct preload! After I awoke from that excursion I am wondering if I need to do all of that. If the races are fine can I just repack or replace the wheel bearings, use new seal and put it all back together? It doesn't have a lot of miles and there was no play in the wheel before I took it off.

    Also, does anyone have good ideas for how to hold driveshaft to loosen bolts that go to transmission after wheel and final drive are off? Asking for a friend....
    #1
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  2. groop

    groop So much to ponder

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    I use a long screwdriver between two of the four bolts. Loosen each with a 12-point combination wrench and a breaker pipe, but do not remove them all the way until each is loosened up.
    #2
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  3. Steve W.

    Steve W. Boxer Pilot

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    Transmission in gear and a screwdriver through the timing hole engaging a flywheel tooth. Cheers
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  4. 190e

    190e Long timer

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    Yes you can clean and re-grease the existing bearings if they look good. With luck you shouldn't have to change the bearing pre-load but you will have to check it. I use Duane Ausherman's shake the wheel test which is a pragmatic method that anyone can do.

    https://w6rec.com/the-5-wheel-bearings/
    #4
  5. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    Generally speaking, if you don't remove the races, you don't need to check the preload, since the race locations drive the wedding band width.. and the wedding band width drives the preload. That might not be the most prudent thing to put in writing, but it's something you can get away with. (This is where someone will jump in to say that immediate death will result from not checking your preload before every ride, every full moon, every creek crossing, and every new set of tires.)

    Yet, don't let the idea of a daunting task of determining preload convince you to run on questionable races. The process of replacing races, fitting wedding bands, and checking preload is not difficult.. and only takes 15 minutes with the right tools. Front wheel is easier, but rear isn't difficult.

    In other words, if your front bearings and races are good, repack them. If your rear outer race is good, you make a judgment call about the captive race, since you can't drop that bearing out to see it. You use a special tool to grease the captive bearing in-situ.
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  6. JGT

    JGT Been here awhile Supporter

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    I use the "shake the wheel" test but did have to adjust wedding bands, shims, etc. to get it close enough. The odd thing is that the torque on the axle nuts makes a big difference (at least with my /5 wheels and bearings). Even tweaking the shims and lapping down the wedding band, I still have to use torque on the axle nuts for final adjustment to avoid too loose or too tight bearings. Turns out it is 25 ft-lb front and 28 ft-lb rear for my setup -- yours will of course be different. But even 5 ft-lb plus or minus has an effect that I can feel when shaking the wheel.
    #6
  7. sprouty115

    sprouty115 Long timer Supporter

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    The Snowbum article on wheel bearings is his masterpiece. It's exhaustively long and has more shifts in storyline than a Tarantino movie. I have tried to get through it several times but I'm clearly not made of the right stuff.

    So in lieu of that I use the Duane Ausherman "shake the wheel test" which allows me to sleep at night.

    Praphrasing - loosen the axle nut and notice how you can rock the wheel back and forth. As you tighten the nut with a torque wrench, notice at some point the "looseness" goes away. If that happens under 15-20 lbs, then the preload is too tight when the nut is at 25 lbs. If it happens over 25 lbs. then the preload is too loose.
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  8. Plaka

    Plaka Brevis illi vita est

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    don't take wheel and final drive off. block wheel so shaft will not turn.
    #8
  9. MonzaCross

    MonzaCross When life throws you a curve, lean into it

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    Just crossed the same wheel bearing path myself a few months back on a 1975 R90/6. Many articles indicate the wheel bearings likely last a couple or a few hundred thousand miles, or maybe the life of the bike. For the rear I bought the Cycleworks tool to grease the right side rear bearing in place and removed the left side and greased. Replaced the left side seal also. Next time I figure I will heat it all up and remove the lot to visually inspect the right rear. Fronts on both sides are easy to remove completely and clean and grease and I replaced the seals. On the /6 at least the 2 front seals and the rear left seal are the same part number if I recall correctly. The front races and rear races on mine looked very good. Dont know true mileage but I would guess at least 50k. If your 78 has the front caps with pin wrench holes figure a clean way to remove them. I hate buggered nuts and such and splurged on the proper long handled wrench but I think you can find two punches that nicely fit the holes, set them opposite and slide a piece of metal or long screwdriver between them and twist.
    #9
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  10. BigWally

    BigWally Been here awhile

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    Where can I find info on the long handled pin wrench to remove the front wheel bearing collars? Thanks.
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  11. tennessee thumper

    tennessee thumper Long timer Supporter

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  12. MonzaCross

    MonzaCross When life throws you a curve, lean into it

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    I got mine from Boxer2valve.
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  13. bogie52

    bogie52 n00b

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    hold the rear brake to move the driveshaft nuts. A 78 should have conventional ball bearings in the wheels with a spacer in between. there were earlier models with tapered roller bearings that needed the spacer in between them to be selected to provide the correct fit for the tapered bearings.
    #13
  14. bogie52

    bogie52 n00b

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    the original BMW tool kit included the required tool, did you check to see if it is there? It was combined with a hook spanner for the fork bearing nut.
    #14
  15. crazydrummerdude

    crazydrummerdude Wacky Bongo Boy

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    The pin wrench in my original tool kit is for the fork caps, not the wheel bearing covers.
    #15
  16. BigWally

    BigWally Been here awhile

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    that appears to be the case with my kit too
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  17. Plaka

    Plaka Brevis illi vita est

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    i made a tool that works very well. i no longer need it. if i can find it you are welcome to it. it is heavy.
    #17
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  18. bmwrench

    bmwrench Long timer Supporter

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    No, tapered rollers were used until 1985.
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  19. cwc

    cwc . Supporter

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    Assuming you meant repack and replace the original bearings the answer is yes IF the bearings feel perfectly smooth as you rotate them by hand. If you use new bearings you may want to check to be sure they don't have too much preload.

    I think you will find that this changed occurred in the mid 80's.
    #19
  20. 190e

    190e Long timer

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    The first examples I know of to use ball bearings in the wheels was the R65 LS and that wasn't until 82 and on the front wheel only.​
    #20
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