CraigC

This is great info! Thanks for sharing.

garrett376

For the sake of completeness, if you are contemplating a big brake caliper up front on a narrow body 964, using a 993 rear caliper with the existing rotors works great to maintain good brake balance. They are a straight bolt-on application, use the same pads, same rotors. Just hook'em up! I got a set of used ones for $200 a couple years ago...

cobalt

I used the 993 rears also. Paid $200 on Ebay in A! shape. Although I used the RS rear rotors.

sturm_old

Kinda what I did. Used 928 calipers, and they looked well used from Parts Heaven and used 993 calipers. Can't remember where I got the adapters for the fronts but they weren't $300.
A DIY if you're handy and have the right tools. My mechanic did the work

I use stock pads at DE and have never had a problem

If i did it over I would have had the calipers painted

Allan
RSA 3.8

rideshootanddrink

Garrett great info! Thanks for sharing. However, I have a question. Which 993 rears should be used: C2 or C4? If I remember correctly they are slightly different. In addition, do you have to do anything with MC? My car is C2, and I think C4 MC is different from what I have. Thanks in advance.

boxsey911

Has anyone replaced C2 2 pot rear calipers with C4 4 pot rears? Is there much benefit to be gained by doing this? And does the bias valve need to be changed when doing it?

cobalt

When I switched over to the big reds I sold my rears to a local 964 owner who switched out the 2 pot rears for my old 4's. At first he said it felt like no difference but now after a DE event he said he does not have the brake fade that he had before. He used to find his brakes would fade after a day at the Glen now it lasts him almost 3 days before he gets the same fade.

I do not believe he did anything other than bleed the system after he replaced them.

cobalt

If this helps the 89-94 964 C4 and C4 TL all used the same MC as the 964 turbo at 23.81mm vs the 20.64mm MC of the C2 these were also electro hydraulic vs 8" vacuum.

When switching over to big reds up front you want the 993 rear calipers from a 993 C2 with the same piston and pad size as the 964 turbo 34/30mm The 993C4 rear calipers use a smaller piston size of 30/28 similar to those used in the 964 C4 but not the C4 TL. I did not change my MC and find the brakes to be perfect with a stronger pedal feel than my turbo with the same brakes but larger MC.

LouZ

So as not to confuse the issue, I replaced my 2 pots with calipers from a 968. Some 944 and 968 calipers are identical to the 964's. The C4 caliper is the same 4pot to which we are referring.

I went to a site that listed brake pad dimensions - that is how I found out Porsche model calipers would fit. Then I just widened my search for used calipers to include those models.

If you switch from 2 to 4 pot rears, you will want to replace the proportioning valve from the stock 2 pot 45 to the 4 pot 55 Bar.

Bill Verburg

964 C2, RSA and C4 rears are identical small body&pad 28/30 for 24mm rotors, RS and 964 turbo are the same small body&pad, but have 30/34 pistons and want 28mm rotors.

993 n/a C2, C2S rears are the small body&pad 30/34mm piston but want 24mm rotors

993C4 n/a C4 rears are the small body&pad 28/30mm pistons and want 24mm rotors ie they are the same as the 964 C2, RSA, C4 rears

993tt rears are 28/28, large body&pad and want 28mm rotors


993RS rears are 30/36, large body&pad and want 28mm rotors

A C2 w/ the 2piston calipers can profit from fitting any of the 28/30 small body&pad 24mm rotor calipers

A c2 w/ big red front can profit from fitting any of the 30/34 small body&pad 24mm rotor calipers

RS use a 25.4mm electro hydraulic m/c
C4, and turbo all use a 23.8mm electro hydraulic m/c, all of the other 964s use a vacuum boosted 20.64mm m/c

The 993 vacuum boosted m/c is 23.8mm and should be used w/ any combp of 36/44 front and 30/34 rear calipers. The smaller 20.6 may work but the pedal feel is very much improved w/ the bigger m/c

when using stock 36/40 front 28/30 rear the stock 964 20.6 mm m/c is fine.

Bill Verburg

Don't go by the pads, there are several variations of the small body&pad 4 piston caliper, you want either the 28/30 or 30/34 for 24mm rotors from the rear of any of several Porsche models.

Bill Verburg

Brake info

boxsey911

Bill this is all great information for me.

So reading between your lines, there would be no point me putting 993 30/34 calipers (e.g. 993 C2) on the rear unless I uprate to big reds or blacks on the front. If I keep stock fronts then look for 28/30 rears (964 C4 or 993 C4) as an improvement over the standard C2 2 pots.

Bill Verburg

As with many things, it depends.

Driver preference is one issue and other factors w/ regard to the car setup.

It's not something the factory ever did but on a 964, which all had much more front bias, but is going to have bias similar to a 993RS which I like very much.

Remember ride height, suspension and lsd are all going to affect the net result

JMPO a low car w/ much stiffer than stock supension and at least 40% lsd would benefit in most cases.

boxsey911

Were the 993 C4 calipers originally painted silver? The reason I ask is I've found some that are described as coming from a C4S yet appear to be in an original silver paint. Apparently the part number on one of them is 20 4672 00