mark kibort

Ok so, ive completed the 928 S upgrade to 330mm rotors 11 to 13" conversion!
worked like a champ, all you need is the adapters, centering rings and the cayanne rotors. 13".

So, now, im a little left out, having only 12.7" GTS rotors on my S4. still better , but not huge difference. Heck, i would even like to use the real 13" rotors from the cayanne as well, but as long as we are doing it, why not just go 14"??

let discuss the offset difference between the caynanne and the S4 rotors an see if we can make some kind of adapter for the axial mount that pushes out the calipers another .7" vs my GTS converison 322mm to 350mm, or really the true adapter is 12" vs 14", or a spacer offset bracket that pushes and moves the calipers out about 1". (similar to what scot did with his 11" rotors going to 13" rotors.

IM thinking of an adapter that is stepped for the offset (which im not sure what the S4 rotor is, and then maybe moving the mounting holes radially with two different thicknesses to keep the radius proper for the caliper ends.

thoughts. IM sure it can be done. Lets do it too! I want big pizza pie rotors!

mark kibort

or maybe with this different offset of the rotor, there is a custom hat available and already made, where i can use the cayanne rotor offset, and then make the brackets. but i guess if you are going custom hat, you may as well just use the same offset as the S4 and then just fabricate a 1" spacer

IcemanG17

Sean has done this........ Just get the two piece 355mm rotors like Lindsay racing sells....then space out the caliper to work..... I think Sean used stock S4 calipers with 355mm rotors...

Hilton

You could upgrade your S4 to 928S brakes/suspension/hubs and the 13" cayenne rotors

mark kibort

i think my fancy spacer technique was a little more cost effective to use the near 13" rotors i have now. (GTS, 964T) ha ha.

Brian, Sean, so where are the pics?? sean already did this with a spacer bracket?? (and using cayanne rotors, 14" ers)??

Hilton

I'm pretty sure you could make a profit selling the S4 bits and buying 928S stuff at 50% off from Mark A

Plus think of the savings in unsprung weight! 928S calipers have to be a couple of pounds lighter than S4 ones.

edit: Oh wait - forgot you ground chunks off your S4 calipers.. scratch the profit idea.

mark kibort

S4 calipers are light! they are made out of aluminum. they way nothing, the S calipers are very heavy. when you have been used to working on S calipers and then you pull off your first S4 caliper, you would think they are made of air.

forget about unsprung weight. if that was important, all the racers would be using S rotors. ! s rotors are about 10lbs , while cyanne rotors are 25 lbs. . Its just not as important as everyone thinks. in fact, there is a direct HP associated with the difference . wanna hear about it......

Fabio421

I'm assuming you are talking about me, Shawn. Yes, I did this but I didn't use 14" rotors. They were the 993TT rotors with S4 calipers. I made a custom adapter to fit these to an early spindle. You can do the same thing with the Big Reds and the standard brake adapters available from the standard suppliers. I just used the S4 calipers becasue thats what I had lying around and I wanted to use the largest rotors available. The 993TT rotors are 320mm.

pcar928fan

I just want the kit to upgrade my EURO S car... When are those going to be available Mark?! Who will have them???

justaguy

Mark
I tried to use S-4 calipers with 355mm stoptech floating discs but it was not possible. The edges of the calipers required too much grinding to clear the the larger OD on the 355's .I would have needed to grind right through the tubing that goes from one side of the caliper to the other as well as the bolt holding the caliper together. I ended up having to go to stoptech st-40 calipers that were made to fit 355mm rotors. Hats made by Mike Simard.

You might be able to do a similar upgrade like you did using only a spacer and grinding the inside edges of the calipers but I think you will need big red calipers to start with

mark kibort

I totally forgot about the grinding of the edges. it wasnt that much going from 12 to 13, so it would be about the same from 13 to 14" right? but if you did it already and the grinding got near the tubing, then scratch that ideal Ill find some used F40 calpers or maybe the stoptech ST40s with use the S4 pad. But, the real question is what would the adapter look like to use the cayanne rotor ? whats the offset of the S4 , GTS, and 964T? the cayanne rotor has a 68.5 hat thickness , while the "S" models have 60mm, which is why we did the adapter with this 8.5mm effecitve offset change. since we have an axial mounting to deal with , we need to radially offset some too, to allow room for the heads of the mounting bolts.

mark kibort

Im going to ping the 944 guys to see if they are interested. dont they have the same calipers and offsets as the 928S?

Ill do a run of 10 sets if we can get some more people .

I have a prototype set of the adapters now, but they require a lot of grinding to work on the calipers, the correct final product requires very little grinding . a little on the spindle mounts, edges of the caliper mount brackets for rotor diameter relief and a little on the caliper braket for mounting clearance.

Benton

I might be interested in a set, as I may be moving the Big Reds over to my 993 and running a larger diameter but lighter weight rotor up front with S4 calipers. It would be nice to be able to use a Stoptech rotor and hat, since the pad size is the same. I have a link somewhere that has dimensions to most of the Stoptech rotors and hats.

Fabio421

The 951 guys are putting GT3 brakes on their cars now. Theres a thread about it running on the 951 forum now.

ubercooper

The issue with GT3 brakes is that they are quite expensive (~3k) and replacement pads/rotors are 3x the price of 928 parts

have you considered Mark Robinson's kit? It uses 2 piece rotors and either stock S4 calipers or big reds/blacks. He mentioned that replacement rotors are only $430 a pair. Once I sell my supercups, thats the first thing on my shopping list. Its not cheap at $1400 but it is the only kit available for 14" rotors that isnt mucho $$$