I know this has been discussed at length, however the search function is not working.

I've got some 993 NB front calipers that I would like to fit to my 91 C2, what are the proper rotors and pads? Are these a direct fit or will I need adapters? I will be also fitting some 4 pot rears, will I need to install the 55bar proportioning valve for a car used for the occasional DE?

Thanks in advance.

 

If you look at Bill Verburg's brake summary (here) you'll see that the plain vanilla 993 uses the S4 calipers. These use the same piston sizes as the "Big Red" calipers and are radial mounted. You'll need an adapter to convert from the axial mount of the standard 964 and I'm pretty sure you'll have to use the thicker 993 rotors. The 993 used a 40 bar proportioning valve so I doubt the standard C2 45 bar part will make any real difference.

Regards

Dave

 

also there is more info specific to 964 here

short answer,
you need 304x32 or 322x32 rotors, there are several different versions of either
the caliper adapter you get needs to match the rotor you use, for diameter and o/s

you will want 993 rear calipers on stock or 951 sport rotors

you will want 993 m/c unless you are starting w/ a 964 C4 that starts w/ a 23.8mm m/c

Best though not necessary is to use a full 993 front suspension and brake setup.

 

One last question:

Will I need the 993nb or the 928 S4 front rotors (this is for a 1991 C2 nb)?

Thanks.

 

If you use 993 struts and hubs you use 993 rotors, most of the ones i've seen that use 964 o/s rotors use the 928 S4 rotors ior 2 piece(hat/rotor) aftermarkets

again 993 and 964 use different rotor o/s for the same size rotors

 

Thanks. For now, I'd like to keep as much of the 964 set up as possible so I'll go with the 928's as it is mostly a street car. I'm not familiar with any of this and appreciate your advice as well as the data that you've posted for public consumption.

 

Your, welcome, Believe me, I know what it's like to have unanswered questions