Kinda stupid cheap but I have them apart and clean.
I know the interior piston surface that contacts the seal ring must be perfect. Must the outside surface that the dust boot/clip fits around be totally blemish free ?
Because of age, rust has done some minor pitting on the pistons where the dust boot clips around. I'm guessing if they are clean and the dust boots fit well it's no big deal.
And, must the raised part of the rear brake piston, shoe side, have to be in a certain position ? Half of the diameter is stepped up,...to be towards the rear, or...? ( Doesn't matter ?)
Rebuild calipers
- alotawatts
- Posts: 438
- Joined: Wed Jan 07, 2009 3:52 am
- Location: Seattle WA
Re: Rebuild calipers BUMP
2nd-ing the question. My 79 has rear seized calipers.
T.Hanson wrote:
And, must the raised part of the rear brake piston, shoe side, have to be in a certain position ? Half of the diameter is stepped up,...to be towards the rear, or...? ( Doesn't matter ?)
Three E12's and one R27






From here on, because of the testing and implied quality I will just buy rebuilts.
If you intend to play with them at all, remove the pads while still on the car. Push the brake pedal to see the pistons are out against the disc. Remove the calipers and remove the pistons as soon as possible there after.
Without the special tools referred to in the repair manual to use air, the best (only) way to get the pistons all the way out of the calipers is by using the closed hydraulic system in the car.
If you intend to play with them at all, remove the pads while still on the car. Push the brake pedal to see the pistons are out against the disc. Remove the calipers and remove the pistons as soon as possible there after.
Without the special tools referred to in the repair manual to use air, the best (only) way to get the pistons all the way out of the calipers is by using the closed hydraulic system in the car.
I think I put the raised part at the trailing edge of the pads. Stating it another was is to put the open portion (cut out) facing down
https://picasaweb.google.com/1030509870 ... directlink
http://www.firstfives.org/bboard/viewto ... er+rebuild
https://picasaweb.google.com/1030509870 ... directlink
http://www.firstfives.org/bboard/viewto ... er+rebuild
1977 BMW 530i
1973 R75/5 BMW (motorcycle)
1973 R75/5 BMW (motorcycle)
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Jamie
Rear Caliper Rebuild
Nice pictures Blaise. Did you bead blast the calipers. The cut outs do face down, using a 20 degree gauge as a position reference. I have two spares in the garage I need to rebuild.
Re: Rear Caliper Rebuild
I did not bead blast these, just used the POR15 caliper paint kit. They still look great.Jamie wrote:Nice pictures Blaise. Did you bead blast the calipers. The cut outs do face down, using a 20 degree gauge as a position reference. I have two spares in the garage I need to rebuild.
But if I ever have to do another set, I will split them and bead blast them. Cleaning them is otherwise a huge pain. I see the warnings about splitting them, but I don't see why I could not replace the O-rings and get them sealed like new. It would also be possible to hone the bores.
1977 BMW 530i
1973 R75/5 BMW (motorcycle)
1973 R75/5 BMW (motorcycle)