r32 gts -> gtst brake conversion help - master cylinder?

[oldenholden64]

Just changed the brakes on a gts skyline to gtst brakes with upgraded rotors and the result is a almost non existant pedal feel.

If you put on the brakes the rear calipers do not do anything unless you pump the pedal several times. If you clamp off the rear brake lines you get a normal pedal. However if oyu clamp the front brakes it doesnt appear to change teh pedal feel.

Would I be right in saying that the gts master cylinder bore is too small and that is our problem?

cheers

[dattoman1000]

Mechanically adjust the rear caliper pistons

I assume its R31 ?

[oldenholden64]

r32

[dattoman1000]

Ah.....so you now have 2 pot opposing rears.
If the rear is the prob...as it points too with you clamping that off and the pedal is fine.....I'd look for something bent or misaligned.
Or pad taper.

Whats the BM # on the side of the original master ?
BM44 is 15/16
BM50 is 1"
BM57 is 1 1/16"

Youd want BM44 minimum......BM50 preferred.

[oldenholden64]

yeha 4 pot fronts and 2 pot rears...and they are brand spankin pads

I had a lok on the master earlier today and I do not recall any of those nubmers being there....

[dbasteve]

It wouldn't be something silly like air in the rear lines/calipers or a shitty old brake line expanding.

If the master was too small you'd get a long pedal, not no clamp force at all.

[dbasteve]

If the problem only occurs after driving then there might be some hub/disc runout pushing the pistons back.

[oldenholden64]

Is there some special way of bleeding opposing rear calipers...
its not after driving, we haven't really drivin it that much because when you turn it on the pedal only has about 1" of throw because of the booster.

[dbasteve]

Same as any opposed piston caliper. Bleed both nipples. Outer first then the inner and repeat.
When fitting dry calipers it often takes a few goes to get all the air out unless you use a vacuum bleeder.

[TRX910]

BM50 is 1"
Youd want BM44 minimum......BM50 preferred.

R32 gts-t has factory 1" master cyl
try switching to one of those if yours is 15/16