Just put s4 disks and calipers allround on my 808 and i can't get any pressure unless i block off the rears. which is great fun but not too legit https://www.nopistons.com/forums/pub...#>/biggrin.png

Its got the 13/16 inch on there and was told s4 rx7 was 7/8 i thort it would be sweet!!!

Is this my problem or should i look elsewhere????



Thanks

pic of the mazda b1600 diff and s4 brakes

well the easy answer is to say if you used the s4 brakes, the s4 master is a good idea....



the bigger the master, the better the pedal feels

I would say yes, because I don't know what the bore size is for the 808 master.



When you do hydraulic calcs the piston size (diameter of bore) will create X pressure against a smaller piston downstream.



4 piston brake's master cylinder should be 15/16" inch. If the master cylinder was bigger, say 1" you use less stroke to produce the same hyradualic pressure. If it was smaller than 15/16 the pedal would travel more to great enough hydraulic pressure

The One on there is 13/16 inch so 1/16th of an inch smaller than s4 i thort that would make it spongy but still work?



When i bleed them (i do it properly) the pedal goes straight to the floor. If i block off the rears at the master the fronts work mint so master aint stuffed

Determine which master cylinder was designed to be used with those calipers and you should be set. No easy way around it I'm afraid.