Searching the J55 Brake upgrades has sure produced some very good information from the forum members! I was going to add my question but thought I might start a new question with a new thread. So, my 1990 is a Z51 J55 car and has sat for as long as 17 years. The A-mold repos have corroded quite badly. It looks as though somebody had to have Red Calipers and just reached threw the Wheels and chip brushed painted them Red! The Rotors look to be a mis match set of cheap'os. They survived the test drive around the block to confirm the L98 was shot, and the Brake Fluid didn't all run past the seals. So, before the next drive with a new Engine, I will be going through the Brake System. My goal for this Car is Autocross and I fully understand that the J55's I have will suit my needs just fine with no need to spend big money. However, if I was not a Hot Roder I would never of bought this car in the first place and being a Hot Roder one must always try to improve things. I have little doubt that I may come to corrosion in the bores of the Calipers and that I will be getting replacement stock calipers. So, if I'm doing so, I understand the 96 GS J55's had some advantages. (no, I'm not concerned if it sez "Corvette" on the Caliper or not) So why not just order replacement parts for a 96 and put them on my 90. So what else is different I'm pretty sure the Rotors are, I looks as though the Calipers might be cosmetic only. If the Rotors are different then probably Caliper Brackets as well? I assume nothing is different in the rear.
Just for the sake of interest has anybody changed the Bosch ABS Controller to one of the later ones? I'm going to guess its tied to the Engine ECM and can't be done plug and play. If there was any real reason to do it in the first place.

 

The 1996 Caliper is supposedly a bit more rigid (thicker web section). Other than that - no differences - same bore size - the 1996 caliper will bolt on to any 13" Rotor C4 (J55). Caliper mountin Brackets are the same, and rotors are the same.

If you ever want to scare yourself - set up a dial indicator on the C4 front brake caliper, and have a friend stand on the brake pedal. The amount of flex is downright impressive, but the truth is the 13" rotor J55 brakes work pretty darn well. You can buy a caliper rebuild kit for the PBR calipers at Rock Auto - they are downright cheap... (Read that as consider rebuilding the stock calipers - and then go looking for the 1996 calipers - which are not that easy to find.

I can't speak intelligently about swapping ABS controllers. I tried that once, with a supposedly identical controller - and the system was quite unhappy. Swapping the old one back resolved the problem.

 

Doing a search I am finding out that the GS Calipers are not readily available at least not on Rock Auto. And that the aftermarket 13" Rotor is the part number for both years. Unless some GS Calipers fall in front of me I think this idea might already be dead. And no, I have no intentions of stealing these parts off my 1996 GS 0694 !

 

I believe all the J55 calipers are the same through the years(88-96), and the rotors are the same as well. The GS/CE calipers ('96 only and say 'corvette' on them) are rumored to be slightly beefier in the webbing area on top. I have both but never looked at them side by side. Looking at them not side-by-side, if there is an advantage in the GS caliper, it's got to be very, very minimal - nothing you'd notice in autocross, maybe road racing where the heat and braking demands are higher.

Sideline - I think you came by my shop years ago when I was in Lynnwood to buy some rear end gears. You still in the seattle area?

 

The GS brakes are beefier but not worth the upgrade IMO. If you need new stuff I'd look at C5 brakes. There is a bracket available so it is a bolt on job. They are a bit beefier than c4 brakes and there are lots of pad options

 

I am. I have since bought a House with a Shop in back in Edmonds now. I don't live in the House but I use the 2600sq ft Shop. Used to be called Maplewood Autobody. 196th and 84th, next to the Fire Station. The Shop is heavenly involved with Corvettes. A friend or two use it as well. C2's, C3's and C4's so far. I'm currently trying to make enough money to pay for this habit of ours in the Berring Sea Fishing. and won't be home for another 6 weeks or so. Some of my work is on my web page x-flags.com

 

Pictures of the calipers