Gary Knox

I think I remember that the 993 TT big reds on the rear of the car are the same ones calipers that are on the front of the 928 GTS. Only the bleed screws and fluid connection pipe need to be changed for them to be used on GTS's or S4's with GTS rotors. Am I correct on this???

Or, is it the front calipers from the 993 TT that are essentially the same as the 928 GTS fronts?

THANKS,

Gary

the flyin' scotsman

I believe so Gary but dont recall what calipers were then used on the front? Massive brakes

Glen McCartney

Gary, I bought a set of used big reds from a 993TT racer, don't know if they were front or back, and I just had to change the connector pipe and bleeders as they were on the wrong side to mount up on my front. I also bought the 2 piece rotors from him for my conversion.

Benton

Nope, the 993TT rears are not the same as GTS fronts. They are the same casting size as S4 fronts but are axial mount with different piston sizes. The 993TT fronts are the same as GTS fronts, but like you said, the balance pipes need to be flipped.

ROG100

I have 993 Big Reds on the rear of my GTS 8>)
GTS Blacks are cheap compared to the 993 Big Reds.

Jim M.

The GTS fronts and the 993TT fronts are the same except for switching the cross over pipes and the bleeder screws. That's required because the 993 has the caliper mounted on the forward side of the axle for weight distribution and the 928 has them on the aft side of the axle. The rear calipers from the 993TT must have the mounting flange machined to allow the caliper to center over the 993TT rotor when installed on the 928.

I've done both, 993TT fronts on my 89GT and 993TT rears on my GTS.

atb

Although the caliper castings on the 993TT rears are the same size as the S4 fronts, the pistons are considerable smaller, even smaller than the stock S4 rear caliper pistons. It would be a nice mod to machine the 993 rears to accept the larger S4 pistons.

cobalt

Gary as other said those won't work on the fronts of your car. I was going to PM you about the for sale thread but I saw this thread. The rear 993TT calipers use the same pad 48 x 132mm as the medium S4 fronts used on the 928S4's. They use a much smaller 28/28mm piston set vs the 928 S4 brakes and the big reds which both use a far larger 44/36mm piston set. Although those were machined to bolt up they would only be of value for a rear mount application. They area also designed to be use with a 322 x 28 mm rotor.

IIRC big blacks can be purchased for a little over $300 each.

Tom in Austin

Does the 993TT upgrade on the rear work with the existing parking brake mechanism or are any changes required there?

atb

No affect on the P brake, its just a caliper swap.

Tom in Austin

Great, so 993TT rear rotors go on fine and all you have to do is cut down the ears on the 993TT calipers a little and no other mods?

Jim M.

Yes, although my original backing plates rubbed on the larger 993TT rotor, so I just left them off. (weight reduction )

Gary Knox

MANY THANKS to all of you who responded. I was afraid my 'old brain' memory might have it backward!

Cheers,

Gary-

hans14914

I happen to have a spare pair of 993tt big-red calipers laying around if you need them.

Thanks
Hans

Chuck Z

Jim, didn't I read somewhere that you also had to change the proportion valve when you went to 993TT rear calipers/rotors?