Rear Brake question

[RideShoot&Drink]

My car is 78 SC, and I'd like to do big break conversion. I have front set which contains new rotors, S4 calipers and adapters. I can get rear S4 calipers, but how do I adapt them? Does anybody sell just rear caliper adapters? Thanks in advance and any help is greatly appriciated.

[Bill Verburg]

The basic S4 front caliper is the same as a 993 front caliper. To use them on a 911 the bleeds and feeds are swapped, in essence they become 993 calipers

One hopes that the rotors are 304x32mm?

For the back you will want either 993 rear or late 965 rear calipers, they both will have the same 30/34 pistons, the advantage of the 965 is that the throat is manufactured w/ the correct width to accommodate a 930 309x28mm rotor, the 993 will need to be opened up a tad.

There are 2 methods of modification to fit on the back of a 911

[list=1][*]fill and re-tap the mounting holes to accommodate the 3" 911 trailing arm holes[*]machine off the axial ears then drill/tap converting them to radial mounts(like the front)[/list=1]

both work fine, #1 is a DIY method 2 is more elegant and more expensive

[tonythetarga]

As I understand it you will also need to do something with your brake proportioning valve. Pre 3.2 Carrera cars will need to be modified.

[Bill Verburg]

As I understand it you will also need to do something with your brake proportioning valve. Pre 3.2 Carrera cars will need to be modified.

If you use the setup i suggested no p/v will be wanted.

[RideShoot&Drink]

Bill, does anybody sell just adapters for those calipers on the rear? Do I also need that proportioning valve that Tony mentions. Sorry, I really don't know much about this, and just gathering information...

[Bill Verburg]

does anybody sell just adapters for those calipers on the rear?

no, the only way to do it is as described above

Here is a caliper modified as described in #1

[RideShoot&Drink]

Bill and Tony, thanks for your help!