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Front caliper o-ring


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This past weekend I found time to bleed my front brakes as they had a mushy feel to them. When I opened the master cylinder, it was pretty much empty. I checked the lines and glanced at the calipers and didn't see any leaks so I bled the brakes and got a nice solid brake feel from the front.


I rode it in to work Tuesday to check it over before state inspection and found the leak. It was seeping from the caliper halves on the left side. So being the mechanical one that I am, I look at this caliper and figure......Someone had to put it together, there's no reason it can't come apart and be repaired. The four bolts were tight and I wasn't sure if they were right or left handed threads. A dab of PB Blaster on the thread ends and a light tap tap tap from my 3/8 impact and out they came.


I find that the o-ring is just flat. It's 21 years old. So I start looking through my toolbox for o-rings and come across a bag with two o-rings. A little snug on the outside diameter but with some massaging it stayed in the indent. I carefully put it back together and tightened the halves back together and reinstalled on the bike. Brakes bled and a satisfactory lever, no leaks. With only the one orifice between the two halves I think the lever could feel better but I'll give it a little time and re-bleed.


The o-ring itself is a viton seal. I'm pretty sure it'll hold up just fine. I don't know if this seal can be gotten from BMW or if it's listed (I'm sure it is) but here is the part # to the seal I used that you can most likely get from any Mercedes Benz Dealer. A 013 997 82 45


Hopefully this helps someone in the future.






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Your o ring may be fine, but the "correct" o rings are available from Tom Cutter at rubberchickenracinggarage.com


The caliper half o rings are not normally avail from BMW


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