spongy pedal

[nui]

hey guys,
can anyone give me any sugestions as to why my brake pedal is always so spongy.
car is a 88 exa.
i have got n15 rotors and calipers on the front, and n13 pulsar discs on the back (replacing original exa brakes on front and drums on back)
i have bled them, but still nothing. the master cylinder was leaking a while ago, i put new seals in that, its stopped leaking, but is still very soft on the pedal.
what else could be causing this?
also what is the brake booster for? could it be this?

any help apprecitaed.

Matt

[MarkZE]

It could be a number of things.

Cheap brake pads will cause this. Standard Bendix pads can be a culprit.

I suspect your master cylinder is now too small with the addition of rear disks that were not there originally. Look at a four wheel disk exa and see what size the master cylinder is.

Have you checked that your rear brakes don't lock up? Adding rear disk to a car with drum brake master cylinder normally locks rear brakes before fronts.