Need help identifying rear brake calipers

[scottrx7tt]

I just bought a 79 wodebody. I am in the process of overhauling the brakes. I was successful finding, and matching the front brakes. The rear on the other hand...
I ordered the front and rears from ********. The rears I received look similar, but have smaller pistons, and the brake line attaches in the side. My current calipers have the brake line that attaches to the back. Anyone know what I should be looking for?

[scottrx7tt]

[Bill Verburg]

Originally Posted by scottrx7tt

front M caliper, 3" mounts 42mm pistons, this should not be on an SC

painted front A caliper 42mm pistons, correct for the front of an SC(except for the paint)


a rear M for an SC will have 3" mounts like the first one above but will have 38mm pistons, the feed shoul be on the side not center

this is a correct rear M for an SC

[scottrx7tt]

All of the pics I posted were for the rear.. What should this caliper be on?

Originally Posted by Bill Verburg

front M caliper, 3" mounts 42mm pistons, this should not be on an SC

painted front A caliper 42mm pistons, correct for the front of an SC(except for the paint)


a rear M for an SC will have 3" mounts like the first one above but will have 38mm pistons, the feed shoul be on the side not center

this is a correct rear M for an SC

[Bill Verburg]

This looks like a front A, but to determine for sure measure the distance between the mounting hole centers, all 3" are SC/Carrera rear M or an earlier front M, big 48mm pistons is front only, smaller 38mm pistons is rear only, 42mm pistons is for '84-89 wide M rear, if the on center mount spacing is 3.5" it's a front A which will have 48mm pistons

[scottrx7tt]

It is 3" from the center of each hole.. So I have carrera rear brakes?

Originally Posted by Bill Verburg

This looks like a front A, but to determine for sure measure the distance between the mounting hole centers, all 3" are SC/Carrera rear M or an earlier front M, big 48mm pistons is front only, smaller 38mm pistons is rear only, 42mm pistons is for '84-89 wide M rear, if the on center mount spacing is 3.5" it's a front A which will have 48mm pistons

[Bill Verburg]

Originally Posted by scottrx7tt

It is 3" from the center of each hole.. So I have carrera rear brakes?

3" mounts means one of the following
w/ 48mm pistons M front
w/42mm pistons 3.2 Carrera rear '84-89
w/ 38mm pistons '69-83 911 rear

note above I posted some erroneous specs, all fronts whether M, S or A are 48mm, rears are either 42 or 38 depending on year

full documentation here on my web page

[djpateman]

Yes, it appears that the rear calipers you had are the Carrera rears for 84 to 88 with 42mm pistons; these should be matched with the thicker rear rotors.
It is tricky trying to identify calipers from the front; a rear shot showing the fluid inlet and mount spacing is far more useful. This is the A caliper with 3.5" mount spacing where the fluid inlet is on the bottom; there are two varieties for the 20mm and 24mm (Carrera) rotors.

This is the M front caliper with 3" mount spacing where the fluid inlet is on the back; there are several varieties all with 48mm pistons for 911, 912 & 914/6 some with a spacer for vented rotors, some without spacer for solid rotors on 912 and 911T. Then there are the 42mm piston versions for the 914/4.

[scottrx7tt]

I bet I had the front carrera calipers also! They looked the same as the ones I just put on. I guess the carrera calipers were just a tad wider and had bigger pistons... Oh well, I already turned them in for a core. The previous owner included new slotted rotors(for an SC I assume). Can I not use the SC rotors with the carrera calipers?

[Bill Verburg]

Originally Posted by scottrx7tt

I bet I had the front carrera calipers also! They looked the same as the ones I just put on. I guess the carrera calipers were just a tad wider and had bigger pistons... Oh well, I already turned them in for a core. The previous owner included new slotted rotors(for an SC I assume). Can I not use the SC rotors with the carrera calipers?

Not safely
3.2 Carrera rotors new are 24mm minimum spec is 22.6mm
older 911 rotors are 20mm new

[djpateman]

Yes, you can use the narrower rotors, but the pistons are extended a bit. You would probably need to replace the pads when they are only half worn to ensure the pistons do not get overextended. I agree with Bill that it is not the safest solution. You want to use a proven system, not a jumble of mismatched parts; the brakes are far too important to mess around with them.