Easy Big Brakes For S Cars

After tracking my 85 S for almost 3 years and adding a supercharger to the car and massive 18inch slicks, my stock brakes left MUCH to be desired in the way of confidence in late braking. After researching and trying different brakes I found 2 threads on Rennlist and put the ideas together and came up with this solution.Thanks to Steve Hattori and Mark Kibort for the original threads and ideas.When I figure out how to post a link to the threads I will.
I made adapter brackets for the fronts that allow you to use S4 or GTS calipers and Huge 13" Cayenne front rotors. And with some simple shims in the back, I could use the larger S4 rear rotors and calipers.
After a weekend at Watkins Glen and 140mph late braking they performed beyond my expectations! The pedal is firm and high and the pressure needed to slow the car down was minimal but not to the point of being "touchy" Anyone who says that stock S brakes are more than enough brake for our cars needs to try this.

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Ed, I want to be able to use the Cayenne rotors on S brake calipers. That is what Kibort was/is trying to do... Will your adapters work for the S brakes too? I kind of doubt it, there is a huge difference between the S and S4/GTS calipers. Also how did you shim the rotor (assuming Cayenne rotors here) so that they would be hub-centric for a 928 wheel (or aftermarket 928 wheel)?

Kibort's adapter is for stock S caliper with Cayenne rotor. My adapter uses S4 or GTS caliper and Cayenne rotor. I made a spacer to maintain the rotor centered on the hub. It is only thick enough to support the rotor so the wheels are still in contact with the hub. As far as wheels are concerned,I know these will fit with Most 18 inch wheels and probably any 17" or 18" wheel that fits a GTS but I would have to try them to be positive.
Unlike Kibort's setup, I have street and track time on them and they do work incredibly well!

Does this set up maintain hub centricity of the wheel? I didn't see the exact phrasing I was looking for, but I think it does... From what I understood in your post.

Are the Cayenne rotors cheaper than GTS rotors (or the cheaper ones with holes that most of us use?). If so I will have to do this on my '95 when it needs front brakes!

Yes James, wheel/hub centricity is maintained so no issue there.
I haven't priced the GTS rotors but the Cayenne rotors were $80 each for the ones pictured. You can also get the slotted or cross drilled versions but they are more money. You can find great deals on the internet, you just have to spend some time searching. These are Zimmermanns also which are good quality rotor.
Remember the reason for these adapters is because GTS or S4 calipers and rotors don't fir "S" model 928 unless you change major suspension components because of the way the calipers mount and the rotor offset would hit the ball joint. This is a total bolt on thing and the performance is awesome.

Ed I put the Zimmermann rotors on from Roger.
but what I would like to know is do I have the big brakes that you guys are talking about

Brad, those are regular S4 brakes I believe and those are smaller than the GTS brakes which are smaller than the Cayenne rotors we are talking about here. So this upgrade Ed has tested is two steps up from where you are now.

That, and honestly the cross drilled rotors are WORSE for braking than a solid rotor. Just save the money and run solid if you can.

Thanks James.
Thanks Jon.

Ed, What was the reasoning for the Cayenne rotors, vs. S4/GTS stuff? Cost? I'm planning on converting my car to S4/GTS spec, but if there is a major cost difference I'd be game for a set of adapters. I'm likely going to run adapters up front anyway, so, I'm just seeing what my options are.

Thing is, it doesn't look like you are using ALL of the available swept area. AFAIK, the S4/GTS setups use basically all of the available swept area. Which on the GTS is pretty substantial.

Jon,

I think it is cost but we will let Ed get back to us on this one. Swept area looks pretty well covered to me actually and even if that is not fully covered there are benefits to having the clamping force further out from the middle of the hub and out towards the edge... so breaking should be greater just due to diameter increase of the rotor...

pcar928fan;11249 wrote:

Jon,

I think it is cost but we will let Ed get back to us on this one. Swept area looks pretty well covered to me actually and even if that is not fully covered there are benefits to having the clamping force further out from the middle of the hub and out towards the edge... so breaking should be greater just due to diameter increase of the rotor...

I understand moving the clamping force further out, but then you end up with brakes like Corvette had, or older Mustang Cobras with a nice rust ring that never gets cleaned off. Ed uses his car on track primarily, so this is of no concern, but on a street car it can look funny.

Actually they don't look that bad at all, but you can plainly see the "ring" that doesn't get touched by the pad surface. I'm just stating in extreme cases (I'm not comparing this setup to a two-piston PBR) the little rust ring left behind is UGLY, just throwing thoughts out there. I would think you could just paint the hats, and the little bit that doesn't get touched by the pad surface, and be GTG.

Either way, I want bigger brakes. If this is considerably cheaper, I'll go this route over GTS/TT rotors. I want a solid faced rotor, so this might be the way to fly.

Jon wrote:

Ed, What was the reasoning for the Cayenne rotors, vs. S4/GTS stuff? Cost? I'm planning on converting my car to S4/GTS spec, but if there is a major cost difference I'd be game for a set of adapters. I'm likely going to run adapters up front anyway, so, I'm just seeing what my options are.

Thing is, it doesn't look like you are using ALL of the available swept area. AFAIK, the S4/GTS setups use basically all of the available swept area. Which on the GTS is pretty substantial.

Cayenne rotors are cheap and so are S4 calipers and brake pads. I didn't want to have to buy an S4 suspension and have to swap it all over to my 85S. This way I have better than S4 brakes and MUCH better brakes than stock S. The GTS calipers can be used also but they are more expensive than S4 calipers and I wanted to stay on the cheap but have great performance.

Yeah, I'm pretty interested in this then. I'm not gonna do the complete swap to my car more than likely. It's expensive and a lot of work. Brake adapters, for the fronts with S4 calipers is what I was hoping to get rather cheaply.

Jon, I agree on the funny looking ring of unswept area...I am NOT a fan of that!

so i have the adapter for the early suspension for my GTS "big blacks" out front, and just some washers for the GTS/S4 rear calipers. will that adapter fit the early suspensions? im pretty sure thats why you made it (not wanting to swap over all that late model stuff)

pic of my mounts

Ducman82;11372 wrote:

so i have the adapter for the early suspension for my GTS "big blacks" out front, and just some washers for the GTS/S4 rear calipers. will that adapter fit the early suspensions? im pretty sure thats why you made it (not wanting to swap over all that late model stuff)

pic of my mounts

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No it will not. This bracket is intended for use on S models only. Before,the options for S models was to buy older pre-S spindles and buy the adapter you have, or replace the whole front suspension with S-4 components. Either way you would have to change suspension parts and re-align the car.
This bracket makes for a truly bolt on and go situation for this Model 928.
This bracket however, will also allow you to use GTS calipers and Cayenne rotors so you would have a different pad and more swept area of the rotor used.

originally this car was a Pre-s or a "competition package car"

here is what i have now. works wonders. but bigger rotors are always nice.

I finally figured out how to copy links.These threads gave me the idea to combine the 2 thoughts and come up with a very good solution. Thanks again to Steve and Mark for sharing back then.
This is the thread from Steve Hattori where he figured out a bracket for aftermarket 2 piece rotors:



forums.rennlist.com/rennforums/928-forum...big+brake+conversion

This is the epic thread started by Mark Kibort which he uses Cayenne rotors and stock S single piston calipers. As yet they are still to be tested by him:

forums.rennlist.com/rennforums/928-forum...big+brake+conversion

Ed, if I were to want/need a set of these adapters and the spacers for the rotors, how much would that run me...?

I'm looking at getting a set of calipers here very soon. This is much easier than swapping the damn suspension.

All I would need are the calipers, rotors, and your adapters/spacers correct? What about the rear? Just shimed with washers from like Lowes? I'd probabaly add stainless lines as well.

Ed, would you mind posting these on RL? Kibort doesn't want to believe me.

Jon wrote:

Ed, would you mind posting these on RL? Kibort doesn't want to believe me.

I remember, perhaps too fondly, of the days with Kibort on Amsoil. I say let Kibort wonder! lmao

Anyone else remember "torque vs. horsepower"

KilnRed;11407 wrote:

Anyone else remember "torque vs. horsepower"

Oh Ya! I added my 2 cents a few times

Jon wrote:

Ed, would you mind posting these on RL? Kibort doesn't want to believe me.

No problem Jon. Done.
Kibort will be kibort. I don't care what he says or thinks. He was on to a great idea I give him that and that's about it. I asked him if he has tracked his setup in his thread just last month and his response was not yet. I did track mine and if he needs proof I have pics and videos too.But I don't need to justify myself to a guy who just likes to argue. I will be at Watkins Glen again on Columbus day weekend with the Niagra Region PCA if he wants to come watch.

Thanks Ed. If you decide to make a couple sets of these please let me know. I'd pay for your adapters and hub rings right now. I just need a set of calipers.

Jon, E-mail me at my homepage. Thanks.

Wilco.....

Noticed the adapters and such are listed on Ed's products page now. Yep, now searching for a decent set of Calipers!

Hello,  I realize this is a very, very old thread, but our the photos still available?  I recently purchased a '84 Euro S, and the previous owner included a bracket kit of some sort and some GTS front calipers and Cayenne rotors. I'm wondering if it is one of your kits? I'm also interested in how you shimmed the rear S4 calipers. I may have to look for a set of those to rebuild.  I don't expect I will have any problems with clearance, since the car has 18" Fikse wheels.  Thanks in advance for any tips!