Ducman82

so here is the Skinny, GTS big blacks, Adapters from 928Specialty.
i got a used rotor to test fit everything. i cant remeber what its off and the only numbers i can find on it are L1520 (OZ) 13177 . but any way, looks like it will almost work. outer pad has a little to much room, rotor surface seams a little small for the pad.
rough messurments are 302mm across, and from bottom to top of hat is 72mm









what rotor should work for that?

Ducman82

im going back to the shop to find out what it came off of here in a few.

Gary Knox

Looks like it may be an S4 rotor - if indeed you have the GTS calipers. Also, it looks like it is on the wrong side, as the internal vanes are meant to pump air OUT of the caliper, not into it.
Hope you get it straightened out.

Gary Knox

Ducman82

ya i just used one of the rotors i know is the left one. part number 993.351.403.01 is what that one is. so i know its not a S4 rotor. what ones should work for this set up?

the flyin' scotsman

Stock GTS rotors are 322mm.

S4 rotors are 304mm.

Ducman82

i know i cant use stock GTS rotors on this conversion. 993tt rotors right?

mark kibort

the 993tt rotors are the same diameter as GTS, that will solve the problem, if the offset it correct. I thought this kit was to mount S4 calipers to a OB, and then use the 993 rotors for the correct offset. is that what you are doing?

I see you are just using some dummy rotors to see if it all fits. but, it looks like the offset is correct, is it? if so, then the GTS rotors will work. I fogot the offset differences between the S4/GTS vs the 993TT, but the net result is the rotor is too close to the tie rod ball joint on the OBs, right?

mk

Ducman82

thats a good question. i know from mounting the caliper that it can be a little wider of a rotor. i mean that one "fits" but one pad gets to travel way more then the other. any one have pictures of the 993tt rotor mounted?

mark kibort

looks like the rotor is a few mm shifted to the inside. is this the only difference of S4 /GTS vs 993?

mark kibort

so,it looks like that migth be a 993, non TT rotor? same offset as the TT rotors?I would think so, if that is so, then when you use the TTs, you will get teh 322mm diameter and the correct offset I would image. cool kit!

Ducman82

im going to pick up some TT rotors in the next week or so. i hear they should do the trick. ill post pictures. cuz everyone loves pictures!

Jim M.

The Big Blacks from the GTS are the same caliper as the Big Reds on the 993TT. The only difference is the Bleed and cross-over tubes are reversed. Thats because on the 928 the caliper is mounted on the back of the rotor and on the 911 it's mounted on the front.

You CANNOT use the 993TT rotor on the 928 assuming the kit you bought is to mount Big Blacks on a 928. The rotor that fits is the 928 GTS or the 965 rotor, P/N 928-351-045-01, LH rotor, solid, 965.351.045.00 rotor, ventilated, LH (cast holes) 322mm, 928-351-046-01, RH rotor, solid 965.351.046.00 rotor, ventilated, RH (cast holes) 322mm.

I converted my 89GT to 993TT calipers and I know the 965 rotors are a perfect fit both in diameter and offset. The rotor must be centered on the caliper, with equal space on both sides, and the rotor must be slightly larger than the pad area. The pictures of the rotor installed is all wrong!

I know nothing about adding these to an older 928 so YMMV.

Ducman82

hummm. on Specialist's website they list the 993tt rotors for thier kit. so im willing to bet they should work. im just wondering if i should use backing plates..... hummm

mark kibort

Jim, this is a special kit for the older 928s and the GTS or S4 conversion, I think.
I dont think the GTS or S4 rotors can work, due to the wrong offset that would put the rotor too close to the lower tie rod ball joint. correct?
mk