On Jul 28, 2020, at 9:56 AM, Bruce Derenski via groups.io <bruce.derenski@...> wrote:

The calculation of system pressure sounds about right. Rough eyeballing of the pedal leverage is about 5:1. Figure your brake foot applies about 50 lbs of force; you’d be getting 250 lbs of force coming into the master cylinder. Divide by the area of the master cylinder piston (sorry; I don’t know the bore size). If it’s a 1.5” bore (just a guess) that would be 1.8 square inches. 250/1.8= 141 psi. 

On Jul 27, 2020, at 8:36 PM, Jim Bollman <Jim@...> wrote:

Thanks Butch, I knew that, just forgot.

Jim...

On Jul 27, 2020, at 8:31 PM, Butch via groups.io <butch46988@...> wrote:

Jim,

While the original rears were 7/8", all of the replacements, for many years have been 3/4", as far as I know.
I do know, that all of the ones that we sol, were 3/4".

Butch

On 7/27/2020 8:12 PM, Jim Bollman wrote:

If you are working with new wheel cylinders did you put the right size in?

Wheel Cyl - 1??? front 7/8??? rear

If they are not new/rebuilt that would be a good place to start looking, could be a stuck cylinder.

Jim...