R32 Sumitumo Callipers

[Birth]

Hi, I want to use the four piston Sumitumo callipers from an R32GTSt in a brake conversion that I am planning. I am thinking of using a 25mm rotor as it fits the stud pattern on the car a little better.

Does it matter how thick your disc is so long as the pistons in your calliper will reach the disc? I understand that heat soak with a thinner rotor is a potential issue .

I am more interested in whether or not a R32GTSt calliper will clamp a 25mm wide rotor. I assume that it will as an R32GTSt is undersize after 28mm which is quite close to 25mm; actually it would probably need to be able to clamp a 22mm rotor (the width of a worn 25mm rotor).

If you take out your brake rotor and push down on you brake pedal (against nothing) will the pistons in you calliper pop out?

Any help would be great!

[Moodles2]

The non-gtr sumitomo's take a 30mm rotor, workshop manual I think specifies they replaced once they're worn to 28mm. Only way to know for sure if they will popup is be a guinea cop

[fletch rb30]

we used to run the gtst caliper on a 10mm disc on a speedway car.

Take the caliper to a machine shop and get them to split the caliper and machine the 2 halves down the amount you need. Its a piece of cake

[Birth]

Wow Fletch; I never would have thoughts of that. Did you try it before you had that done, I assume that it didn't acocomodate the 10mm disc with-out doing it, but I guess I am still hopeful that I could use a 22-25mm disc with-out doing that.

[fletch rb30]

it definatley wont fit a 10mm disc on the stock calipers, the pistons will fall out before the pads get close enough.

You could probably run the 22-25mm disc on new pads, but when the pads wore you would be in danger of the pistons popping out, or binding up and locking the brakes.

The machining would be pretty cheap, there are only 4 bolts holding it together and while your at it you could get a seal kit from nissan and rebuild the calipers.

Pete puts the cut down calipers on many speedway cars, they are a relatively cheap caliper and work well enough for the job.