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I was just looking at the Vanderzanden site at their rotors and I see where they offer the stock rotors but also offer the 13" rotors as a Z-51 option. Is there an easy way to tell just what is on the car other then jacking it up and pulling the tires?;help

And does the 13" rotors make that much of a difference?
I could be wrong, but I am pretty sure the 13" were a ZR1 only option. However, many people are upgrading other model C4 cars with the ZR1 brakes, thus giving you the opportunity to go 13". This would require more than just changing the rotor. You would also need the bigger caliper and hardware.

Otherwise, even with Z51 on a 1985 model, you should have the 12" variety.
Been there, done that...

I just upgraded my brakes to the 13" (HD option) setup.

You need to replace your rotors, calipers and caliper mounts. The caliper mounts obviously relocate the caliper to fit over the larger disks. The calipers also must be replaced as the new disks are also thicker.

It is not hard to do the work. If you want, I have so digital pix of the job.

Oh, and yes, there is a difference. First couple times I pulled up to a stop light, I was stopping 10' short of the line. Much better at speed and no noticealbe fade.

I purchased the parts through ebay and another supplier online. I even got cross drilled rotors. Everything cost me less than $500 (the xdrilled rotors cost $200).

Now my only question is what to do with the 12" parts I took off.


btw, I think the 13" brakes were a RPO, but I don't know which years. 95-96 all had 13" brakes.
brake upgrade

I've been looking into the upgrade myself-and the one thing I've seen- that you also need --to go above 11" rotors (my 87)--is 17 inch wheels otherwise not enough room for the calipers--my 2 pennies........scott..:s

The Z-51 option from 1988 on had 13” front rotors and the backs were 12”. The ZR1 also had the same rotors. But you could not get the Z-51 option on the ZR1.
The larger brakes make a difference only under hard use. But they also look cool.

I looked up the specs on the later cars, and none of the base cars have 13” rotors. Even the current 2002 do not have them.

I upgraded my 86 road race car from the stock 12's to the 88 Z-51 package with the 13" rotors in front and dual piston calipers. For racing the difference is huge.
At 135 mph I can brake at 200 feet later
(400 vs 600) going into a 70 mph corner.
The big rotors are essential for high speed work.

"The larger brake package, included previously with Z07 and ZR-1 performance options, was included for 1995 with all models".
from The Corvette Black Book. These brakes were also standard on all '96 models. The only difference between these and the GS or CE models were cosmetic only.
Guys....all this is Great....but nowhere can I find the answer to my question....
It appears that in 88 the 13's became the option with the Z51. Prior to that all had 12's. Although they do make retrofit kits...which are expensive compared to what I can get all 4 rotors for. I am still looking at which type rotor....drilled, milled, slotted...twisted, knead and braided. Ever notice that every other part begins with turbo? What the heck has turbo got to do with brake rotors?
Venting I know....sorry...:hb :upthumbs
The 13" rotors are pretty rare. I know a few people that bought new 89 cars for autocross and ordered the big rotors.
When I upgraded my 86 to the 13" rotors, I had to buy a special bracket to mount the caliper. That was for the new 88 dual piston caliper. I don't know if the single piston 85-86 caliper will work with the big rotor.
Drilled vs slotted: I have run both on a GT-1 road race car. The drilled seem to work better to keep the temperature and fade down. Cracks always develop from the holes after 5-10 weekends. The slotted ones tend to develop cracks all the way across the face. They actually have a shorter life than drilled.
For a street car, 13" rotors do look great, drilled rotors look better, and the dual piston caliper is an improvement. Drilling costs money and may not be needed for street.
If you are looking at a brake catalog, turbo probably refers to European cars
where turbo cars have bigger brakes and all the handling equipment. I wasn't really sure what your question was, so I tried to fill in the blanks, hope it helps.
I doubt the caliper will work.

My dual piston from my stock 12" setup would not work because the 13" disks are thicker than the caliper will accept. Hence the need for the other calipers.

A good question though, what type of brake lines?

Eagle, I just emailed you, but if you really want a 13" setup, I think my conversion cost $250 for brackets, rotors, and calipers (and set of good pads too!). It was used, and there are more to be had from the same source. (I would post, but dont have it with me.)

If you are interested let me know.


Did you get my email? I am interested in the calipers and rotors...let me know. Thanks!

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