What kind of master cylinder do I need?

[slepe67]

I thought about posting this on the HAMB, but, fear of a lynch mob made me come here.  Probably a better choice, since you guys build for speed.

I have a 32 Frame (bodies are being mulled over, I have a glass roadster, but am considering taking up a good deal on a 32 3 window-this way I can run my full cage all the time, as opposed to having a roadster cage for the street, and one for LSR)...I digress.

I have a deuce frame, and I'm running '77-'88 or so GM discs up front, and a Ford 8.8 rear end, with discs out back.  I am not keeping this car "traditional", I am building it to go and stop FAST.  I was looking at Tim Cunha's 32 3 window, and he has his master cylinder bolted to the firewall, with swinging pedals.

Since I'm running discs at all 4 corners, what master cylinder do I need?  Bore size?  I am consdering Wilwood's, jsut want to check before I drop some $$$ on the wrong thing, as I have a problem with that lately...I'm open to all options.  Thanks in advance!  JL

[manta22]

JL;

It's hard to say what diameter master cylinder you will need for your '32 without knowing the full details. It's probably going to be around 3/4" to 7/8" but whatever you do, put in an adjustable pressure limiting valve in the rear brake circuit.

Regards, Neil

[slepe67]

I'm trying to word this without sounding like a smart Acura, so don't take it that way...

what else would have to be known? Brake line size?  I'm lost on this one. 

I'm starting from absoultely nothing here.  Just a frame, and some disc calipers and rotors.  All parts are OEM.

[manta22]

JL;

There are a few things that will help you calculate the required M/C size:

Caliper piston diameter, number of caliper pistons, brake pad effective swept radius, brake pad coefficient of friction, tire rolling radius, etc. then calculate the PSI needed with your pedal ratio.

Or... you can simply start with a 3/4" diameter and see if it works OK; if not, go bigger or smaller. Companies like Wilwood make master cylinders that are identical except for the internal piston diameter-- this makes them easy to swap if a different size is needed.

Regards, Neil  Tucson, AZ

[dwarner]

Have you tried the Wilwood tech line? They will need some info such as vehicle weight, etc.

DW

[slepe67]

thanks guys

Neil, I'll try to find all that info out, shouldn't be too difficult.  The internet is BEAUTIFUL!

DW, I could GUESS, but I would also imagine mine is not the first 32 roadster/coupe they've crossed.  I didn't even think of calling them, thanks.