I think the point that we are all trying to make here is that there are levels to each upgrade with respect to improvement. How you use the vehicle plays a large part in your overall satisfaction of the modification route you choose.

Moving from the base 12 inch to the J55 calipers is a huge improvement and there are loads of posts from people here on the forum that have done this and have been very pleased with the results. A large number of J55 parts are being listed now more than ever which makes the upgrades cheaper as well. Be sure to service any used caliper before bolting it onto your vette though if the age or usage level is in question.

Next up is adding in the GS caliper to the mix. Frankly on the street I don't think you are going to notice it that much compared to the J55 calipers. I ran them on and off track for years and the improvement was slight, but added to the overall pedal feel improvments I was getting with steel braided lines. You can still spread a GS caliper. Some additional mods to the caliper can also be made regarding the pistons and what not as well, but thats out of the scope here.

PROS: Its a nice mod if you have the calipers already and gives a nice look from the street.

After a couple hard turns and heavy braking on a heavy brake style track setting, you may find yourself wanting a bit more. Again this depends heavily on the track, your driving style, and your expectation level. If given the choice of GS vs. J55 calipers and nothing else, sure bolt them on.

Another positive of this mod is that you can still use the late model c4 saw blade wheel with this, which are rather inexpensive and often available used. All in all a nice upgrade.

CONS: Can add to the overall cost of the upgrade if the pricing is not in your favor. The price as come down drastically over the past couple years. Again if you need a replacement at the track, not quite as easy to come by.

Next up is the c4 to c5 conversion. Its a nice upgrade for weekend track, autocross, and a nice upgrade to the street in my opinion. Yep we make adapters for it. Is it the end all for track conditions?
Not by a long shot. There are numerous aftermarket kits with fixed monoblock caliper setups that provide better braking than the stock c5 stuff.

PROS: What does make it nice is that you have in general a wider selection of pad and rotor choices available to you. In most cases the consumable parts such as pads and rotors are cheaper than the same part for a c4. Most auto parts stores stock a c5 rotor as well. Nice to have when you want a stock rotor on a track weekend. In general they are easier to find in stock. Been there done that.

CONS: This upgrade vs. the J55 package is that you are going to need the later model A-mold style wheels or a similar aftermarket wheel to give you the clearance you need.

I think the gentleman above is going to be very pleased with the J55/GS upgrade choice he has made and until he decides to move to a heavier track situation or a time where he needs more brake with less fade than he is getting today. He will be very pleased with the dramatic improvement it makes over the stock 12 inch setup. Its a good choice for a lot of people.

I would like to repeat what is often said here though. Be sure that when making an upgrade of any kind that all the other parts are in tip top condition. Examples here include, the master cylinder, brake fluid, brake lines, (we recommend new or aftermarket braided steel), pads, freshly turned or new rotors, etc. And always be sure to always properly bed the pads and rotors after completing any brake work.

 

On paper stock '88 12" brakes for stopping distance show 168 feet from 70-0. The '96 Grandsport shows 164 feet.

 

That wouldn't all that surprising since they both had anti-locks and used the same size brake pads. After several stops however, I think the larger and heavier GS or J55 brakes would have less fade then the 12" brakes.