Bad Karma

I know I can upgrade my JL9 (12" Rotors) to the J55 (13" Rotors), and be fine. But are there there any goofy restrictions on me using Grand Sport Calipers?

Solofast

Earlier cars can't legally upgrade to the bigger rotors since that would take a non-Corvette caliper bracket. So long as you are swapping out stock parts for stock parts and not using somebody else's bracket and it all bolts up you are fine.

Umrswimr

Not unless you own a Grand Sport or intend to convert EVERYTHING over to one. IIRC, GS brakes calipers are different than the J55 ones, correct?

Umrswimr

If he converts the entire brake system to J55, he should be fine, right?

vetteracer92

So, what is special about the GS calipers to make them better? Just a thought, being a GS, wouldn't they come with the J55 option? If so you can change the calipers also since it comes together in a package.

2HorsePower

I think the GS calipers are essentially the same as the J55 calipers except for the "Corvette" lettering on the GS version.

Bad Karma

The J55 was the option code for that years upgrade to 13" brakes. The Grand Sport Calipers were only available in '96 and they read "Corvette" on the caliper face. Since they were not available in '90, I didn't know if that would matter. I know there is some wording about changing within the model year range, but I wasn't sure how that works.

RX7 KLR

Should be no problem on a 90', just use the OE parts, 84-96 C4s are on the same line in BSP so can even use the GS brakes. The only thing you could not use is a "ZR-1" brake, they are on a different line, but they have the same 13" stuff anyway so no loss there.

FWIW most of the fast C4 SP guys always went with the smaller brakes to save weight. The extra rotor will do nothing to help you on an autox course. Sure if it is a dual purpose car it would be nice to have the bigger brakes on a road course, but they are just more unsprung weight to carry around on a Solo.

In stock class the GS caliper is only legal on a 96' GS spec car.

2HorsePower

From 2008 Solo Rules for Street Prepared category:

"15.1 AUTHORIZED MODIFICATIONS

C. Equipment and/or specifications may be exchanged between different years and models of a vehicle if (a) the item is standard on the year/model from which it was taken, and (b) the years/models are listed on the same line of Appendix A (Street Prepared Classes). The updated/backdated part or part to which it is to be attached may not be altered, modified, machined or otherwise changed to facilitate the updating/backdating allowance..."

Corvette ('84-'96) are on the same line in the Appendix for Street Prepared. Upgrading to the J55 brakes (which was a factory option for 1990 anyways) should be perfectly legal in B Street Prepared (or in A Stock class for that matter if the option change is complete). Upgrading to the Grand Sport calipers should be legal in Street Prepared, as long as you don't have to alter, modify, machine, or otherwise change something in order to use them... Just my .02

jwt1603