Brake Issues Still! Help

[speedtripledan]

Bias pedal box with .625 and a .7 girling master cylinder 5 to 1 pedal ratio

pushing on m16 calipers.

Round scotland the front brakes kept feeling up with air, no fluid loss. Approx 100miles and the fronts were gone.

changed m/c like for like problem still exists except brakes are gone in 3miles.

Tonight changed front circuit on to the rear .7 mc and rear circuit on to .625 front mc. Went out and the front brakes were so much better locking nicely on moderately hard push and with 3 miles no rear brakes. So problem must be the .625 Cylinder causing the air. But the dilemma now is the fronts felt better with the .7 Mc do i leave it like that? if so what size rear? Really had a gut full of this now!!! 2 faulty .625 Cylinders !! Grr !!!!!

[brumster]

Are they genuine Girling's? There are some nasty far east copies kicking about, even got the Girling casting, but with pretty *bleep*ty/marginal seals and manufacturing quality.

Is the piston rod operating cleanly, perpendicular to the piston (or as near as)? Age old problem on the GTMs was that the master cylinder was not located square to the piston, so they used to wear one edge of the bore prematurely. Now granted, this shouldn't happen that quick, but it was a common enough problem.

 

Maybe if you can't get a solid vouch for the master cylinder quality, move to a genuine AP racing master cylinder. I see a girling m/c these days and I just think, "Chyaaa, right"....

[speedtripledan]

They are girling style supplied by obp who supplied the pedal box. Probably as you say chinese crap

[Guest 2b cruising]

Worse still Indian.

[Longboarder]

Sounds like you may have a bias bar clearance problem. The movement of the twin cylinder pistons is not equal. The bar needs to be set so it can skew as you push the pedal. On mine at rest the front connected side is well back and on application it is well forward. The rear piston hardly moves. To allow this to happen about 4mm of play needs to be present in the bias bar setup. If I setup my bias bar with little play the rears are full on, the bar skewes as far as it can but there is not enough movement for the fronts to be applied. Difficult to explain but a pic helps if I can find one.

 

Nigel

 

Can't find a pic so did this with paint in win7. (give me XP paint any day!)

Edited May 26, 2015 by Longboarder