I'm running Granada Disc in the front and drum in thr rear with a M/C from a ranger. It takes a lot of pressure on the pedal and I'm trying to lessen it. The Ranger M/c is a 1 or 1,1/16 bore and I've been told that a 7/8 bore would be better. What M/C are people using and what bore is it ?? Thanks Rick
I could and I see that those are 15/16 bore, which would be closer to the 7/8. I have talked to people at Wilwood and they want the piston size on the disc and the rear cylinder size to tell me what I should have. The guy at ECI told me I should use a 7/8 bore, so thats why I'm trying to find out what people are using. He said that using the smaller bore would take less foot pressure but would have to travel more. All in all a better feel for stopping.
I'm interested in this too. I have disc/drum , and a factory 76 master. Although they stop very good I still think there is to much travel on the pedal...
if theres too much pedal travel cant you remove the master cylinder and adjust the rod from the booster if you have power brakes? isnt there a threaded bolt under/behind that rod that allows you to adjust in or out for that specific reason?
The one thing different on my car is that I'm running 4whl disc brakes and 4 piston calipers. I've done this on Camaro's, Mustangs, and hot rods.............and have always used 1" MC bore or bigger, but I like to push hard on the pedal...........I've never liked power brakes......on a race car or fast street car..............just my own opinion on staying out of trouble. I assume that the Granada calipers are only 2 piston and not 4, which makes a huge difference in clamping power. Again, it depends on the pedal ratio, automatic pedals have a different ratio than the standard. I have always looked at trying to achieve 1200psi under severe (foot trying to push through the floor) conditions..........and a minimum of 1000psi regardless. Having the pressure checked at any reliable brake shop will give you an idea of what your system is doing. I'm not sure if your brakes have a spongy pedal............if they don't then you should be ok, but if they do you either have some air still in the system or you have "slack" (for a better term) in the system. I agree that a lot of people have a misconception that a bigger MS will create more pressure. While a larger MS creates a larger displacement, it takes more force to create the same pressure as a smaller bore, while a larger MS will take up system slack with less pedal stroke, it will take more force to create the same system pressure. To put this in perspective is that if you were to go from a 3/4" MS bore to a 1" MS bore you would have to exert about 75% more force, but the "slack" would be taken up in less than 1/16" of pedal travel...............there is always a compromise. So, once more we come to pedal ratio, the ratio must be correct or you will either not have enough travel to use all of the piston stroke or have too much travel which will bottom out the piston in MS..........IMHO I have no knowledge of a Power brake setup that has any adjustment, but if it does you should be able to get to 7 to 1 ratio....I would think.
Do you know what the surface area of the piston is. If so it should be pretty simple to determine what size MS piston is needed, but my guess would be 7/8".
Piston diameter is about 2.60", so piston area per front caliper is (3.14)*(1.30)^2 = 5.31 sq.in. approx. FYI, my manual brakes & clutch pedal setup gives a 6:1 brake pedal ratio (factory type pedals). It really boils down to you getting a 7/8" bore m/s and trying it.
