Brake caliper rebuild 1977 R75/7

Edselhead · Post by **Edselhead** » Thu Jun 03, 2010 12:11 pm

The front brake caliper on my R75/7 starting leaking fluid so I purchased a rebuild kit from BMW. Has any one attempted this rebuild? Is it a fairly simple procedure to install this kit which includes the piston? The directions mention the use of special tools- are they really needed? Would appreciate any advice you have on this task. Thanks!

schrader7032 · Post by **schrader7032** » Thu Jun 03, 2010 1:59 pm

Yes, I did my '78 R100/7 several years ago. Pretty straight forward...I don't recall any special tools. I had a little corrosion which resulted in a small leak past the squarish o-ring. You may have issues removing the pistion. If so, people have hooked up an air hose and forced air in through the bleed hole. Just be sure you have something to catch the piston using some rags or something, or force air in at a low rate.

Not sure if Snowbum's article goes through the rebuild process perse, but he gives good insight into the bleeding and brake set up process. You should have the single ATE disk brake.

http://bmwmotorcycletech.info/brakes.htm

This website has info on adjusting the brake to give maximum braking force.

http://www.airheads.org/content/view/184/98/

You might want to consider replacing the brake line if it hasn't been so far. After a number of years, it can weaken on the inside and squeezing on the hand lever only balloons up the hose and doesn't transfer all the fluid to the brake. I personally prefer the original rubber lines from BMW. Snowbum talks about other options.

Good luck! The biggest hassle may be the bleeing process, but be patient. Also, I think Snowbum mentions having some rope holding the hand lever part way open over night to allow air to migrate out. And one thing I was conscious of was not pulling the hand lever all the way back to grip when bleeding. If you have corrosion in the master cylinder bore, you'll just rip the diaphragm and create another problem that's not so fun to fix!!

Edselhead · Post by **Edselhead** » Fri Jun 04, 2010 10:57 am

Schrader, Thanks for the info. I will give it a try. The rebuild kit was not cheap so I was hesitant to get into something that was over my head. I did replace the brake line last year when I put in a new master cylinder.

schrader7032 · Post by **schrader7032** » Fri Jun 04, 2010 11:40 am

Most times the piston really doesn't need to be replaced. But I believe the dealer only sells a complete kit. However, my last leak required only the outside dust boot to be replaced. I was able to buy only the boot from Ted Porter at the Beemershop in northern California. He sells other parts separately as well. Even though I was just replacing the boot, I had to disassemble the whole caliper anyway.