@rene4406 posted:To compare the volumes of fluids needed to operate the front calipers and my new rear calipers, since the diameter of the two parts of the master cylinder are the same.
Another question, does anyone know what length of travel of the caliper pistons is taken into account to calculate this volume? I guess it's around 2 or 3 tenths of a mm?
You may actually be getting to what I was thinking? I don't see the reason that two different sized pistons were used in the front calipers unless possibly it was felt that the master cylinder could not adequately operate the caliper if all four pistons were of the larger size?
I still have my original master cylinder stored in my Pantera parts drawer.
I went to the master cylinder that Hall Pantera sells. It is definitely a Ford item and likely will interchange with a Mustang.
It has no issue with supplying pressure to the calipers but what I have learned through the years is that you can modify both the pressure and the volume by using different diameter pistons and piston bores in the master cylinder.
From memory, I think that the bore in the original Pantera translates to about the stock size of a regular production Mustang. 7/8"?
This balances the pressure that you feel in the brake pedal with adequate pressure to the calipers.
When I went to fully manual brakes in my 68 GT350, I changed the master to a 1-1/8" bore. That was from a F250 truck application. It made the pedal high and hard but reduced the travel of the pedal to the point that you just touched the pedal for braking. This desensitized the brakes for racing so that it was more difficult to lock up the brakes in a panic stop and it kept the car braking straighter.
Eventually I went back to the power brake set up and added rear disc brakes. The master bore wound up a 15/16".
As far as the OD of the caliper pistons that I am using in my Pantera, the front uses 4 @ 49.327mm (1.942") and the rear are 4 @ 41.275mm (1.625"). Considering how big those are in comparison to the stock originals, I don't think that you should have an issue with lack of capacity with the stock master cylinder and stock calipers? I don't think that there is any kind of an issue there? Why the original piston bores are two different sizes is a mystery to me but really doesn't matter?