Wilwood Balance beam master cylinders

I'm using Wilwood compact master cylinders with a balance bar. The front JFZ 2-piston calipers are fed by a 7/8" master cylinder while the rears (8" Mustang rear with drum brakes) are supplied by a 1 inch bore master cylinder. I'm using a 10# residual valve in the rear and a 2# in front because the master cylinders are lower than the wheel cylinders. Has anyone had experience with a similar setup and would you have any recommendations for an initial setup?

 

I am running a Wilwood balance bar with 4 wheel drums. I would set the bar in the center and try a few hard stops in a safe location. You're looking for the front wheels to lock just before the rears. Shift the bar toward the MC for the end that needs to lock sooner. You may need an observer for this, but I was able do it by myself. This is how I did mine.

Once you get the balance right for dry conditions, you'll need to retest in the wet. You never know when you'll get caught in the rain and you definitely don't want the rears to lock first when it's wet.

There is a limit to how far you can go. I can't remember what it is, though. If you can't get the balance right with the adjustment available, you'll have to change the MC bore sizes.

Mike

 

Thanks Mike, I talked to the Wilwood Tech guy and went with his recommendations as far as bore sizes. I'm certainly no expert when it comes to determining bore size vs. piston bore capacity and then throw in the wet road factor as well. Maybe
I should go with the remote adjustment cable to make it easier to adjust on the fly.

Fred

 

With drum brakes the M/Cyl size for the rear is way off! Don't mean to sound like a "know it all" but a 3/4" front master is plenty big enough to operate a pair of front callipers. I would use a 5/8" or .7" for the rear. The wheel cylinders are only 7/8" or 1" (guessing here) and with the 1" master you wont have much rear braking at all. (no mechanical/hydraulic ratio compared to the front). You will be surprised just how much rear brake you can run without locking up.
Regards,

 

Just for the OP's info, I'm running 15/16" wheel cylinders in the rear with a 13/16" bore MC.

You are correct about the amount of brake force you can get away with on the back. These cars are balanced more like a mid or rear engine car and need a lot more force in the rear than a "normal" car.

 

There is actually quite a bit to engineering your brake system. Pedal ratio, m cyl volumes, wheel cyl volumes, caliper size etc. I have used balanced bar systems in several of my cars and one thing I found with a dual m/cyl you can get away with smaller m/cyl than you would on a conventional single m/cyl setup. You have to be careful when going smaller because too small will not move enough volume. I would just start with what you have and with the balance bar in the middle or slightly favoring the fronts. Drive and adjust is really the easist way to do it.

The proper way would be to put a pressure gauge on the front and rear system to see the actual pressure being created by your combination of pedal and m/cyl. A smaller cyl will create more pressure but require more pedal travel. Personally I wouldn't go this length unless you brake system does not work well after trying a bunch of different settings with your current setup. I have actually done this with my car but I just have some GM Corvette looking m/cyl on mine. I was having brake issues and come to find out my system had absorbed a ton of water and my calipers where sticking. A tear down and clean out along with new fluid fixed my problem.

 

Thanks for the info. I hope you are right regarding my M/C size. At $75 a hit and the mess of changing out cylinders. I don't want to have to change too many!!