'VETTE PHASE

I thought that I read on here one time that the difference between the base brake caliper and the Z51 caliper was that the Z51 has a bigger piston. I am changing my 05 from an A4 to an MN6 and the donor car is a Z51, so I am changing the suspension out also.

The Z51 caliper is the one on top (with some red paint on it). The base caliper on bottom is still attached to my car. The base piston is a lot bigger, but has a thinner wall. I guess I just had them backwards, but wouldn't a bigger piston be better?



Base vs Z51






Z51 piston diameter






Base piston diameter






Z51 piston thickness






Base piston thickness

PowerLabs

I knew that, but I've always wondered why; the bigger piston will increase rear brake bias, but Corvettes have Electronic Brake Force Distribution (EBFD), so brake bias is dynamically varied back to front depending on traction available anyways, so I don't see the point...

I'd love to find out... Anyone?

nwc6

Z51 has bigger rotors, so the brake torque would be greater with the same sized piston as the base. I wonder if the actual braking force on the Z51 rear vs the base rear is pretty much the same, while the front is actually increased?
I read a post in the autocross section where the rears brakes were getting much hotter than the fronts. I thought it was the other way around.

oldmansan

If that is the rear caliper I've read the Z51 piston is 3mm smaller than the base, so that would be about right. I was always told the front calipers are identical.

San

0corvette pilot

yes, the rears are smaller, but as you point out, they are also thicker. Its all guessing, but I think the larger rear rotor allows to use a smaller piston diameter, and they maybe went with a thicker piston to improve heat dissipation, although it seems like not much, but it is about 28% thicker.

'VETTE PHASE

You are correct about the front calipers. They measure out identical.

Z51 on top, base on bottom




Now I just wonder what affect this will have if I leave the base rear brake calipers on it. I know a lot of others have done it, but I wonder if anyone has compared it back to back with a regular Z51 with the smaller pistoned rear calipers.

oldmansan

I honestly think if you drove two cars back to back where the only thing changed between the two were the rear calipers, you'd be hard pressed to tell the difference.

San

overrev64

The reason for the smaller caliper was discussed last year.
http://forums.corvetteforum.com/c6-t...?highlight=z51

Post #8

'VETTE PHASE

Hard to believe that that never came up when I did a search. Thanks for that info though.






Here is the main answer if you don't want to read through the thread:

ChevyLsII

I know this is an old post, but do you have a side by side pic of the base bracket compared to the z51 bracket?

timd38

They look identical, only 1/2" taller.

HOXXOH

I'm guessing the HD brake option and the base C6 starting in '07 with the F55 option have the same size caliper pistons as the Z51.

Actually you can tell the difference when you swap rotors from a J55 equipped car to the JL9 size. The rears don't bite as well and it makes it easier to do burnouts at the dragstrip.