2.4S rear brake question

[elflamo]

Hi all, let me start by mentioning that I've searched the archives thoroughly, but I might have overlooked this...

I'm working on the rear caliper rebuild of my 2.4S 1972 (yes, needed to split the caliper halves). Questions I have:

- pistons were stuck, not to the sides (could turn them easily), but to the guiding pin. I experienced this with the front pistons as well, although not to this extend. I had to weld a bolt to the piston center to be able to lift them out without damaging the sides. After removel I found only little rust on the pistons. Question: what is this about this center pin and the pistons clinging so much to them, is this normal, will this improve once I lube the pin and/or the clamping bit of the piston with piston assambly lube?

- can new pistons be acquired for the rear, maybe stainless steel? Our host tell me they can't provide

- Am I correctly understanding that the standard rear calipers on a 1972S are M calipers?

- do many of you have bad experience with reusing the little round caliper seals that go in between the caliper halves? Where can I get these in case I decide to get new ones. From the various threads I understand our host doesn't provide these either.

Hope you can help me, thanks in advance!

Dennis

[cmcfaul]

I have rebuilt my M calipers a few times. I never split the halfs. The rebuild is very easy. Just a knuckle buster in getting them nice and clean. Buy a rebuild kit that includes the round gasket, dust covers and the pin duhickies.

Used but rebuildable M calipers are a dime a dozen. I would go that route rather then splitting the calipers.

Chris
73 911 E

PS the Rear M calipers are different from the front M calipers. Same pads but smaller pistons in the rear.

[Bill Verburg]

Yes, '72 use M rear. All the rebuild kits and parts used to be available through the regular dealer channels. I was told that due to liability issues(the lawyers strike again) that would no longer be the case.

I haven't seen M pistons in ss, if you maintain the brakes annually, by exercising and changing fluid there will be no problem

The caliper half o-rings are
4x 901.351.928.10 (front and rear seals are the same)
seals for rear M are
2x 901.352.998.00


use Uninsiliikon Tk 44 n 2, 50g tube, Porsche part # 000.043.117.00

[kucharskimb]

i just rebuilt mine. didn't split the halves. parts available here.

as far as the removal of the pistons, i just used an air compressor and inserted the nozzle into the bango fitting port. i then gave little bursts on the trigger to push the pistons out. i think on one, i had to go to 100psi on a 1/16" nozzle to finally blow it loose. place a thin piece of wood between the pistons to prevent damage.

don't let the "pop" scare you when the piston comes out. and mind your fingers.

[elflamo]

Thanks for the fast replies.

Bill, are you suggesting the use the lube not only for the rebuild, but also to alleviate the issue with the pistons back-ends sticking to the center pin?

Thanks again

Dennis

[Bill Verburg]

Originally posted by elflamo
Thanks for the fast replies.

Bill, are you suggesting the use the lube not only for the rebuild, but also to alleviate the issue with the pistons back-ends sticking to the center pin?

Thanks again

Dennis

both

[skinnerd]

SS pistons are definitely available for rear M calipers.
I did them on the rears of my 73E in the past year.
My originals were really bad....super rusty from the seals outward.

I "think" I got them from Stoddards in Ohio.
Simple replacement with new seals and dustboots.

[Steve Marshall]

flamo,

Are you sure you need the center pins? I've had calipers that have them, but most of them don't. Which makes me question whether you even need them or not?

As for the center o-ring those are a bit of a mystery. When I rebuild calipers I never split them because I don't have a source for that o-ring. My mechanic does have a source so he splits them when in certain instances.