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Thread: Sticking front wheel

  1. #1
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    Sticking front wheel

    The bike is a recently acquired 76 R90S. I have not had a chance to actually ride the motorcycle, but I have managed to address a couple of minor issues. While rolling the bike around the garage this afternoon and checking tire pressure, I noticed the front wheel was extremely to turn. No obvious cause. I have done nothing with the brakes. Any suggestions for where I should start?

    Rickt

  2. #2
    '99 '03 '06 National Co-Rally Chair Friedle's Avatar
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    Quote Originally Posted by r65lsk75c View Post
    The bike is a recently acquired 76 R90S. I have not had a chance to actually ride the motorcycle, but I have managed to address a couple of minor issues. While rolling the bike around the garage this afternoon and checking tire pressure, I noticed the front wheel was extremely to turn. No obvious cause. I have done nothing with the brakes. Any suggestions for where I should start?

    Rickt
    Hopefully there is a service history with the bike. When were the brakes last serviced, fluid changed, how old are the pads? Make sure the bike is properly sorted before you actually take it for a ride. If you are not familiar with the particulars of the bike, find somebody to help you. Have you joined the Airheads Beemer Club yet? www.airheads.org

    Friedle
    Ride fast safely

  3. #3
    Registered User lmo1131's Avatar
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    Could be a number of things brake related; stuck pad, corroded piston, contaminated brake fluid, etc. Unlikely, but wheel bearings might be knackered.

    ... pull the wheel and take a look.
    "It is what you discover, after you know it all, that counts." _ John Wooden
    Lew Morris
    1973 R75/5 - original owner
    1963 Dnepr

  4. #4

    stuck wheel

    Quote Originally Posted by r65lsk75c View Post
    The bike is a recently acquired 76 R90S. I have not had a chance to actually ride the motorcycle, but I have managed to address a couple of minor issues. While rolling the bike around the garage this afternoon and checking tire pressure, I noticed the front wheel was extremely to turn. No obvious cause. I have done nothing with the brakes. Any suggestions for where I should start?

    Rickt
    Best to put the bike on the centerstand and remove both calipers. That's an easy way to determine if the brakes or wheel bearings are the culprit.

    Worked on a R90s a few years ago that had the exact same problem. The caliper pistons were frozen.

    That's why it's best to flush brake fluid annually.

    RickR90s

  5. #5
    Liaison 20774's Avatar
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    Probably not the issue, but you might try cracking the bleeder(s) on the calipers to see if there's trapped pressure. Likely it would have dissipated over time. But if there's a blockage in the return hole in the master cylinder or the brake lines are original rubber, they could prevent fluid returning or artificially keep pressure applied to the pistons.
    Kurt -- Forum Liaison ---> 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!

  6. #6
    Quote Originally Posted by r65lsk75c View Post
    The bike is a recently acquired 76 R90S. I have not had a chance to actually ride the motorcycle, but I have managed to address a couple of minor issues. While rolling the bike around the garage this afternoon and checking tire pressure, I noticed the front wheel was extremely to turn. No obvious cause. I have done nothing with the brakes. Any suggestions for where I should start?

    Rickt
    Is the bolt that holds the caliper eccentric ? I recall that you rotate the bolt to adjust the angle of the caliper housing to the brake disk prior to securing the end cap on that bolt.

    If the angle is offset, then the pad(s) drag on the disk. It is even more pronounced with dual brakes.
    JWMcDonald
    2016 R1200RS (current)
    2003 R1150RS (prior) / 1978 R80/7 (prior) / 1966 R69S (prior) / 1972 R75/5 (prior)
    Windsor, California

  7. #7
    Registered User Anyname's Avatar
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    Brake master cylinders have a tiny return hole that allows the fluid to bleed back into the reservoir when the handle is released. If that is blocked, it can prevent the pressure in the calipers from releasing the pads. That having been said, I'd agree with the thought that it's likely that the calipers are seized.
    BMW R bike rider, horizontally opposed to everything...

  8. #8
    #4869 DennisDarrow's Avatar
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    Try rebuilding the master cylinder....Good luck

  9. #9
    To diagnose this, remove the calipers from the disc and pull them back holding up with a wire to keep tension off of the brake lines. Now roll the bike, if it rolls fine. The calipers more than likely need rebuilt. This is very typical on the disc brakes.

  10. #10
    John D'oh
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    (Please don't use dot 5 silicone based fluid in your rebuilt ATE system).

    ATE brake calipers and master cylinders suffer from lack of proper service more than most brake systems I've dealt with. They really need serviced yearly. Use only DOT 3 or 4 fluid and bleed the brakes at least once a year when you get them working again of course. The amount of money you are about to spend on a dual disc set up will ensure your attention to this service in the future - I always say :-) The commentary above by others has pretty much nailed the issues really. Sounds like they each know from experience. Water condenses and settles in low places causing rust pits to form in master cylinder bore and on the caliper piston. The resulting coarse surface destroys seals causing failures in the system one of which is a 'stuck piston' clamping a brake disc. Several folks in the US repair ATE master cylinders by replacing the damaged bore with stainless steel inserts which are then fit to your new M/C piston. The calipers themselves are probably fine but there may be damage to the pistons.
    I'd make it stop first. Then go. Start fresh with new BMW hoses and brake pads. You might even consider some contemporary modifications to improve the performance of the ATE system.
    John D'oh

  11. #11
    #4869 DennisDarrow's Avatar
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    Quote Originally Posted by Na Cl K9 View Post
    ATE brake calipers and master cylinders suffer from lack of proper service more than most brake systems I've dealt with. They really need serviced yearly. Use only DOT 3 or 4 fluid and bleed the brakes at least once a year when you get them working again of course. The amount of money you are about to spend on a dual disc set up will ensure your attention to this service in the future - I always say :-) The commentary above by others has pretty much nailed the issues really. Sounds like they each know from experience. Water condenses and settles in low places causing rust pits to form in master cylinder bore and on the caliper piston. The resulting coarse surface destroys seals causing failures in the system one of which is a 'stuck piston' clamping a brake disc. Several folks in the US repair ATE master cylinders by replacing the damaged bore with stainless steel inserts which are then fit to your new M/C piston. The calipers themselves are probably fine but there may be damage to the pistons.
    I'd make it stop first. Then go. Start fresh with new BMW hoses and brake pads. You might even consider some contemporary modifications to improve the performance of the ATE system.

  12. #12
    Ditto to all of the above. And even after I did everything listed above, my R90S always had a bit of brake drag on the stand. Not noticeable while riding.
    '61 Clubman's Gold Star, '13 690 Duke, '13 Daytona 675R, '14 Street Triple R, '17 1290 GT (gone but not forgotten: '76 R75/6, '84 R100, '76 R90S)

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