The S brakes were fitted with a lower pressure limit valve (softer spring) & smaller rear cyls simply to help stop the rear brakes locking up (IE: to make them work "less" effectively)

this "combination" is perfect when discs are fitted to the front,
the factory did their job right

"IF" you still have large rear cyls & the std "mini" limit valve spring, you "WILL" have locking rear brakes with discs fitted on the front, especially dangerous in the wet

simple as that !!!

If you have a low peddle, then you have an adjustment issue of some sort,,, shoe or pad travel is exsessive for some reason

if you have a "spongey" peddle, then you have air in the system (generally) or a bend brake pad or swollen/guey hoses etc

if you have a low & spongey peddle, then you have a combination of all of the above

again---> simple as that

there are some people who have fitted the larger master cyl (.75)
& this will give a much higher, firmer peddle, when everything else is perfect
but then more peddle pressure is needed.

edit--> but to answer your question, yes fitting the smaller rear cyls will give a slight increase in active peddle height, provided everything else is in perfect working order, but it will be barely noticeable.

one thing people often forget about is the amount of movement the rear limit valve piston has, this does creat slight bit of peddle travel depressing the spring/piston inside it, quite often heard & felt.

Love this thread.

Love this thread.

. I contacted the boys at 888 Racing today to ask for their input and it would seem it is not all that simple either. .

There is a reference table here of all the different combinations (master, wheel cylinders and discs etc) fitted to UK factory cars. It's probably a good idea to stick to a factory combination if possible so you know the F/R balance and fluid capacity will be OK. (Click to enlarge)

It's been 16 years since I have driven this car, only the last couple for the rebuild though. I wouldn't say it was a very low pedal, just doesn't feel right.

You should be able to have an almost solid pedal with only an small amount (~10mm?) of 'soft' travel. I suggest that you clamp off all 4 flexible lines and test the brake pedal for each individually, after 16 years the hoses may have deteriorated inside and are flexing internally....