Benton

Negative, 993TT rear is approx. 10mm shorter casting than GTS/993TT front. 993TT rear uses the same pad as S4/993 front.

993TT rear caliper is almost identical in size to S4/993NA front, and appears the same aside from the axial mounting and the flat logo surface (hence all of the confusion here). The length of the casting is negligibly longer.

993TT/GTS front uses a pad with the same length as S4 front, 993NAfront, and 993TT rear; however, the annulus (height) of the GTS/993TT front pad is larger.

If the caliper is axial mounted, came from a pre-monobloc caliper Porsche, and is a larger casting than S4/993NA/GTS rear--all of which apply to the caliper in question--it HAS to be either a 993TT rear or a 993RS rear. In all likelihood, it is a 993TT rear, as no one in their right mind would install a 993RS rear caliper setup on a front-engined car without some serious brake MC/plumbing/bias modifications.

I'll put $20 on it that they are 993TT rear calipers.

BC

Well, They did suggest a bias change when they were doing these. As I recall the "secret" was that it was a 993TT rear caliper with some sort of offsetting machining done.

The increase in whatever you were trying to increase was not large enough from a larger rotor'd rear with standard S4 brakes to make it a popular idea. Especially since track cars usually take weight OFF the rear of the car.

Benton

I run 993TT calipers all-around on our race car, and the rears are definitely under-utilized. I am actually considering switching the 993TT setup over to my 993 (for rice points) and installing the 993NA caliper setup on the race car, but with a spacer on the front caliper to install a Stoptech 330-350mm rotor.

The Stoptech ST40 calipers are very similar (in size and appearance anyway) to the 993NA/S4 fronts, and use the same pad. Therefore, Stoptech rotors are compatible with 993NA/S4 front calipers, just have to find a hat with the correct offset, machine a spacer, get the correct-length bolts, machine the caliper at the edges to match the rotor radius, and work on the bias.

atb

Maybe I should mention that I'm running these same rear calipers on the back of my S4 (pictured below). I did it for the bling factor, but I've got to tell you that my S4 with this set up (big red's all the way around) has the nicest feeling brakes of any car I've driven.

Benton

Hey Adam-

Have you driven a 964 or 993? If so, how did the pedal feel to you in comparison? I ask because the brake pedal in my 993 is much firmer than the brakes in the race car. I am sure there are several factors, but I am guessing most of it stems from being boosted more and a little extra leverage on the pedal. It has stayed consistent through several bleedings/flushes (no air, no boiling), different pads, and two seasons of track driving. No issues, just a softer pedal than I would like. I guess that is the compromise you make when you don't convert every system in a street car to race-level.

Don't get me wrong; they work wonderfully, but they are just a little too "soft" for my liking. It has nothing to do with the stopping ability--just the feel. I really would like to switch over to dual MCs with a balance bar, but I need to just get the darn thing finished and back on the track so we can enjoy it.