Master Cylinder Bore

[201fireman]

I believe our Montes (mine is a 72) came with a 1 1/8 bore master cylinder. Would a 1" bore work also or would it not fit or be a negative effect?

[MCfan]

Todd, comparing the performance of a 1 1/8" dia master cylinder to a 1" dia master cylinder using simple physics and math shows that the smaller 1" unit will actually deliver 26.5% more brake line pressure for the same foot pedal pressure. Or, the smaller 1" unit will deliver the same brake line pressure with 79% of the foot pedal pressure. Of course, in either case, the 1" dia master cylinder piston will also have to travel 26.5% farther to displace the same volume of brake fluid.

 

I can't attest to the advisability of the swap you are considering, but at least on paper, the smaller diameter master cylinder will create more braking power, not less. If the smaller diameter unit bolts up correctly AND you have enough pedal travel, it might be worth a try. I'm guessing that one or more members have tried this swap or know otherwise if it will work or not.

[stangeba]

Great information! When my rear brakes need adjusting the pedal get's closer to the floor than I like.

I wonder how many "replacement" masters caused some kind of problem never linked to being the wrong size? Take it back, get another one problem gone? (or is it?)

Bruce

[Sam (Bones)]

1 1/8" is the stock size

 

I would try a 1 1/16" before a 1"

 

I'm having a similar issue, before I change I need to verify what I really have