Wilwood brake help

[redss86]

I am needing some information on rear calipers. I was going to buy the Wilwood Forged Superlite calipers, but I don't know what size piston bore I need. I am going to put them on a Ford 9" under an 86 Monte Carlo SS. I am thinking about going w/ SC& C's G5 front suspension w/ the C5 brake components, and eventually installing Wilwoods Superlite 6 Big Brake Kit when money is available. If any body can tell me what the best bore size for my vehicle would be, I would greatly appreciate it. Also, would this setup work with my stock master cylinder?

Thanks again for any and all help.

[fuzzyonion]

For the calipers, a rule thats seems to hold for most stock street applications is to not go less than 50% the effective area on the rear pistons as you have on the front, and not go more than 75%. Use the piston size to calculate the effective area (pi[Rsquared]). Add pistons on only one side of opposed piston calipers.
For more info on performing the math visit http://www.outlawdiscbrakes.com/faq.html

If you go as large as 75%, you can use a prop valve. If you go smaller than 50%, you may not get as much rear braking as desired, resulting in the fronts overworking.

The stock 1/2-3/4 rule seems to apply to vehicles assuming the rotors are ~ the same diameter front and rear, and applies to street vehicles of similar weight/wheelbase/cg, and 4wl disc. (Camaro, Mustang, Trans Am, Corvette)

For the master, most power brakes seem to use a master bore piston area which is ~14-18% of the front caliper piston area. There are many different masters, and different calipers of the same bore sizes may take more fluid to extend the pistons than others, so it's best to use a master you are sure came from a similar system to which you are using, or larger, and use more boost.
There is math to go with it, but it is rather involved and you have to know the values of many variables. http://www.carcraft.com/techarticles/76680/index3.html

Or you can go the "I done this, and it stops great" route, assuming everyone would recognize a problem if it presented itself.

[427v8]

OK I used the 1.38" bore Dynalite callipers on the back of my Vette and the SL 6 on the front with a 1" bore manual MC.

Bad Idea. Not enough brake.

I've since upgraded to the 1.75" dynalites in back, mucho better, But I have now pulled the 6 pistons in favor of 4 SL4's because I'll pick up about 25% more wheel torque which will make me feel much better.

( the 6 pistons are for sale btw ;-)

I would recommend something simular with the Monte.