Which master cylinder for 4 wheel disk brakes

BillGrissom said
Can you elaborate? I did quick research and find no info that the MC itself is any different. What makes the system a diagonal or F/R split is the external plumbing. Link below gives some brake design info, including prop valve adjustment:
www.sae.org/students/presentations/brakes_by_paul_s_gritt.pdf

I found some guys questioning if some BMW's have a special "stepped MC", i.e. different bore size for the 2 pistons:
www.bimmerforums.com/forum/showthread.php?1776935-Master-cylinder-(-diameter-
But no reason to think that is true of the cloud car MC I used. It sure looks like the same bore size externally. Indeed, I have a spare MC rebuild kit for it, so I'll look at the piston again (don't recall but one diameter). Even if it were stepped, that would just affect the split to the R circuit and I have an adjustable prop valve so could tweak it perfect regardless.

nm9stheham said
Not sure I understand this last part....?? Trying to figure out how the piston for the rears gets a different force applied on it than the piston for the fronts with the same bore size....

To put it simply, the primary circuit piston is the only one actually connected directly to the brake pedal. So, you push on the pedal, actuate the primary piston, which then builds some hydraulic pressure to actuate the secondary piston, at least until the initial spring force has been oer come. In a F/R split you'll find that the balance between the two return springs is altered to at least reduce the travel in the secondary piston vs the primary piston which therefore reduces pressure in the rear circuit and creates a bias, at least instantaneously during the apply due to hydraulic latency. This is probably enough to keep the rear brakes from locking first in a perfectly biased system. I know it sounds pretty minor.

You may also find in some cases that the outlet ports have orifices which would be smaller for the rear brakes to reduce flow.

The stepped piston master cylinders are pretty rare.

Will you be able to get away with your cloud car master cylinder? Possibly. It may have some funky characteristics. You're welcome to try it. I'm not sure what you're using a 7/8 cylinder with for foundation brakes but it seems a little odd to me for the normal stuff used on these cars. Pedal travel is probably gonna be pretty long.

At this point we do almost all the brake bias in the ABS/ESC module using both orifice sizing to slow the build rate at rear wheels vs the front and also by using electronic brake force distribution. Plus most stuff anymore is diagonal.