checking brake fluid pressure

I am running a Wilwood dual Master cylinder system with a balance bar for front to rear bias adjustment. With moderate to heavy pedal pressure ( she said - wife mashing the braking pedal while I was monitoring the gauge) I'm looking at about 800 psi on all 4 corners. Adjusting the brake bias rod doesn't seem to make a lot of front to rear psi difference? Maybe a 100 psi difference with the adjustment all the way in ether direction. Is this normal or should I be seeing a bigger psi change? I haven't "skid" tested it yet.

I believe the purpose of the adjustable bar for brake bias is to control the rate and the amount of fluid moving between the two systems, not the pressure.

The adjusters I've seen usually apply one master before it applies the other master, there for reducing the effect of one set of wheels locking up before the other set has applied. The amount of pedal pressure doesn't change, only when, and how much fluid is applied. Make sense? Gene

Pressure would be changed by bore size.

Yes, makes sense. Thanks, I needed that.

You might want to consider applying max pedal yourself and have the Missus read the guage just to confirm.

Kevin

i believe you should see between 1000-1200psi at the front calipers. if you are only getting 800, you need to step down in master cylinder bore size, increase the caliper bore size, or check your pedal ratio to see if it may be off some. see if your boss can view the gauge while you stomp the pedal. i can't remember, are running power or a manual setup ? were you having any issues stopping ?

Thanks guys. Good idea on switching. Her idea on pedal pressure might be totally different than mine. I'll wipe down the creeper this morning. Not really having any braking problems. It's a manual system. 1" master bores ( what Wilwood suggested for my set up ). Pedal ratio is pre-set by Wilwood - reverse dual master system ( masters sit on the back side of the firewall ) comes with pedal and pedal mount. GM intermediate car size calipers with 11" rotors.

i think your pedal ratio on that setup is about 6.2:1. that's similar to the one i modified to turn the master 90* behind the dash on my humpback, and that's what the ratio was on it. that should be ok. i'm using a .944[metric 15/16"] minivan master and large GM[impala] front calipers with 12" mopar cop rotors on the front with 12" wilwood rotors and GM metric calipers on the rear. got an adjustable prop valve to get the front/rear bias. rear tires are 33x17w and fronts are tiny 165's. that ought to be fun stopping with that combo.
if you switch and can't get roughly 1000psi, use the calculator that "feets" came up with, or mark wiliams calculator. plug in the pedal ratio, master size and caliper bore. it will give you the psi and leg effort necessary to obtain it. let us know what you come up with.

Per Williams calculator, plugging in a foot force of 150lbs ( per them, middle of "normal" range ), 1" master bore, foot lever ratio of 6.32:1, I should come up with 1200 psi. Wife and I switched rolls today and IMO I had to use excessive force to come up with 800 psi. - again, just my opinion. Per Wilwood, with the GM metric calipers I am using ( 2.38" piston dia.) they recommend a 7/8" or 1" bore master. I went with 1". Probably should have went with 7/8". Hind sight . . . . . . . . . .!

i checked a couple of calculators before deciding on my combination of parts. i was looking for a "power" brake feel with a reduced ft.lbs. effort. if i ever get this thing under it's own power, then we will see if my homework paid off. luckily, there are a couple of smaller masters i can use if necessary, and i have room for a slightly longer pedal throw. i always have believed you need to stop good before you go. remember : "speed doesn't kill, it's that sudden stop that does you in !"