RED SHARK 1990

Has any members here have done the switch s4 to re-trofit new GTS calipers and rotors? Do we need new studs for the thicker rotors? The black GTS one. Anything else i need to know...Thanks

Ed Scherer

You'll probably want to use the bigger dust/splash shields.

928.351.083.04
928.351.084.04

(click the pics for big versions)




No need to mess with studs (at least for the cast-hole rotors I used).

Different pad wear sensors, too.



I think the damper plates between the pistons and the pads are different, too, but I don't remember for sure.

Vilhuer

Just calipers, longer mounting bolts, rotors and shields are needed. Hose is also different IIRR but S4 version works.

Brett928S2

Hi

Hold on its not that easy...

If you increase the rear or front braking force your brakes will be unbalanced....you will have to alter the front/rear bias, and if you dont and try an emergency stop....you may well find the car spins

All the best Brett

pcar928fan

That is one of the upgrades that makes me ask, "why"... Are you REALLY running out of S4 brakes? Even on track? I have run my S4 with stock rotors/calipers and Pagid Orange pads at the track for thousands of miles and only had minimal brake fade EVER (normally NO FADE), my race car has S4 brakes and has NEVER faded (of course it weighs 1000# less than an S4, so that makes sense). The GTS big blacks look so much like the S4 calipers that I bet if you didn't have them side by side you could hardly tell them apart. I like the idea that Mark Robinson is developing personally and that is keep your S4 calipers and use 14" rotors with them... that will nicely fill the inside of an 18" wheel...different dust shield (or none at all) would be needed of course, but it is supposed to be a bolt on affair with a bolt on stand off for the caliper.

Bret, I think the ABS system is smart enough to figure it out...I have a turbo 911 brake bias bar on my S4 and have NEVER had a problem. I have different master cylinder altogether on my race car (no ABS) and have never had a problem... The rear brakes on an S4 are no different than on a GTS are they???

Brett928S2

Hi James

Thats interesting about the bias....I didnt know it could cope...

I also wondered WHY ....as my S2 (with standard S4 Brakes) has stopped me perfectly from well above any speeds Porsche designed them for lol...

All the best Brett

pcar928fan

Brett,

My S4 stops better than ALL my other 928's! Even with stock pads. I am not sure if the brake vacuum master cylinder is better or if it is simply that Turbo 911 Bias bar putting more brake towards the rear, but when I have not driven that car for awhile and then get in it I have to be VERY CAREFUL for the first few stops because it stops so hard it will send you through the windshield! I LOVE the brakes on my S4!!!

mark kibort

Paleeeezzze!!!

there are no issues with this in the change to GTS rotors and calipers

mark kibort

Many know that I have just mounted GTS rotors on the stock S4 system. basically, you get the same stopping power as the GTS that way. the stock S4 calipers are the same ones used in the F50 ferarri, Anderson uses these and we both use the exact same brake pad. the only difference between his and mine is that he has 14" rotors and mine are just under 13" (GTS or 964T rotors)

All you need is the longer GTS mounting bolts and some dremel work on the edges only of the S4 inner caliper area where it would touch the rotor for the wider diameter. (and you can lose the dust shields or bend them back a bit to fit, as they are kind of a pain to switch as you need to remove the hubs to get to them)

what is the goal??

I raced pretty competitive for many years with the S4 system, and only when I had the stroker, and increased my straight speed by about 5-10mph on most tracks, the stock stuff would fade. now, they are marginal , and I would love to go 13.5" or 14" rotors when I find a source for the rotors that have the right offset.

pcar928fan

MK, you might check over on Pelican with Mark Robinson, he has something cooking. Not sure if it will work for your application, but it well might be just the answer you are looking for.

mark kibort

Just need a hat with the right offset , and maybe coupled to the reasonably priced rotors that would be bolted to them. otherwise, Im game for something else too that would fit and give me another 1/2-1" diameter larger diameter rotor to be used with the same calipers

pcar928fan

I think that is what he has done...sourced all the proper components (I think some of them had to be custom made, but he had that done) and put them together as a "kit" so to speak.

MK, here is the link:

http://forums.pelicanparts.com/porsc...86-5-928s.html

terry gt

Go for the GTS brakes they work great , my 91GT would lose its brakes on the track , the larger GTS brakes were good . Remember 17" rims are a must with the GTS brakes 16" rims will not fit.

atb

I had problems with the bias when I switched to the big reds up front. Not so noticeable on the street, but on the track it was a problem. 55 was too much, the 33 is not quite enough (I've got the big reds on back as well), something inbetween would be ideal.

jthwan22

I did the S4 - GTS conversion using Porsche stock pads. It squeals like a pig when I am doing light braking. What am I doing wrong?