master cylinder sizing?

[big B]

I'm trying to figure out what size master cylinder to use on my 73 z. I will be using the Arizona z 12.2 4 piston kit for the front and stock z32 rear kit(using the s13 rear irs). I don't want to use a booster and have the option of using either a 7/8 or 1 inch master. I hear pedal effort will be too high for the 1 inch but will the 7/8 be too small for this brake setup?

[EvilC]

I believe you can go with the 280zx MC....size of 15/16 bore. That is what my setup will be with Arizona Z brakes front and rear. As far as pedal effort, I havn't driven my car yet...lol But someone can correct me if I am wrong here.

[blueovalz]

The 15/16" is a popular size, but that's using it with a booster. I would compare the new piston area and compare it to the OEM piston area. This will provide some clue as to whether a larger master cylinder could be used WITH the booster. Take the booster out of the picture and things will change, specifically the effort required to stop the car. The good thing is that you've now got a larger diameter rotor, which helps in the leverage required.

I've no idea how small you could go with the master cylinder, but IF the caliper areas are comparable, and a 7/8" is an OEM size, then my uninformed guess would be that you may need a master cylinder smaller than 7/8" when you remove the booster (I may stand corrected on this). Again, the larger rotor may help you stay with the 7/8" size.

[JMortensen]

Just based on anecdotal experience from others, I bought 3/4 and 7/8" masters for my dual master setup. I expect that they might not be the right size and I may have to change them to get what I want, but I'm guessing that 7/8 would work. Might be a bit high on the pedal effort. I've heard of people going as small as 5/8" but then the pedal throw gets a little long. I think you're in the right general area with the 7/8.