Our car has Westfield (AP) 4 pot calipers on the front and normal sierra calipers on the back, it also has a .75 master cylinder to operate both the front and rear.

Problem we have is the pedal is quite soft (yes it is bled correctly), I'm thinking the problem could be down to either:

a: a single master cylinder isn't big enough to do the lot, or........

b: the cheap and nasty (but brand new) master cylinder is faulty..

Anyone with any ideas?

Cheers
Richard

I have a 0.75 Mk.1 Fiesta master cylinder doing my front and back sierra calipers that I got off Ebay. I had problems with a very soft pedal too and it turned out that one of the joints was very slightly sucking air in but not weeping fluid. It was more noticable over night when it was hitting the bulkhead. May be worth just nipping your connections up.

if the master cylinder seals were leaking then the pedal would very slowly sink to the floor with sustained foot pressure

Are you saying that you have single circuit brakes?
If so a single .75" master cylinder will probably be too small.

Anyhoo you really need dual circuit brakes......

For a kick off a 0.75" master cylinder is not to small.

A few items to check
(1) On most Loscost iRS suspensions the rear calipers have to be unbolted and turned so that the nipple is upper most when bleeding.

(2) If you can find no obvious leaks get some one to press the pedal hard while you examine every single pipe union.

(3) You can test the master cylinder by unscrewing the pipe unions and substituting a bleed nipple which after a quick bleed should give you a rock hard pedal -- test the master cylinder by applying pressure gently and gradually building up pressure as this tests the mastercylinder for internal leaks.

However if you do a web search you will find light alloy calipers are widely recoginised as sometimes causing spongey brakes, this is caused by a combination of reasons.

(4) Calipers mounting brackets are not presenting the piston faces (and pads) 100% square to the disc surface in all axes.
This causes the caliper mounting braket to flex every time the pedal is pressed hard.

(5) Air can be trapped in the calipers -- try the same cure as with Sierra rear calipers.

(6) Some multi pot light alloy calipers flex --- they are nowhere near as rigid as Sierra cast steel calipers.

If you want decent brakes use Siera calipers and live with the unsprung weight and lack of bling.

[Edited on 3/8/09 by britishtrident]

[Edited on 3/8/09 by britishtrident]

^^^ Voice of reason! Never understood the need for fancy brakes on a 7 (unless maybe on the track)..

Dan