checking brake pressure

[ks71z28]

I want to check the brake pressure at the calipers. I know of the testers on the market and looking to see if anyone I know has one, they are like $300. What are good readings? Any other tests that are done?

thanks

[LTorres]

I want to check the brake pressure at the calipers. I know of the testers on the market and looking to see if anyone I know has one, they are like $300. What are good readings? Any other tests that are done?

thanks

There is some math that can be done to calculate a given pressure at each caliper (you may be aware of this). Since vehicle's vary so much in weight, design and suspension characteristics many things are considered by engineers (the guys making the big bucks) before any range of pressure is placed in a given system.

If nothing has been changed from stock your on safe ground. That is to say of course the system is fully functional and all components in the brake system are working properly. Each system as it sits O.E. is capable of producing a range of different psi readings depending on Power/Manual brakes and the dimensions of each individual component.

If I had to say a range of psi readings, that most rear wheel drive, front engine cars use, I'd say between 500 psi and 1100psi. Obviously the amount of pressure is directly propotionate to factors such
as Manual or Power brakes, Pedal ratio (Mechanical Advantage), and the amount of pressure you apply upon pedal depression.

I would also say that most guys are concerned with this pressure being equal from side to side on the same axle.

[ks71z28]

I will be using a testor that gois in the caliper between the piston and pad. I will be testing it next week. My set up is pretty typical of most 2nd gen guys are running. I have a dual diaphram booster, 1.124" master, and 2.75" bore calipers at all corners. I also have an adjustable prop valve. The car feels week under hard braking. My 68 firebird seems just as strong with less high performance parts. I will get back with the numbers when I get them.

[fuzzyonion]

Why not test the line pressure with a $40 gauge first? If you find that the calipers dont put out enough, you'll have to do that anyway.

The equalizer gauges that go between the pad and disc can be found for less than $200 for a pair. They are used for checking dragging and/or unequal brakes.

A hydraulic piston's output can be found by multiplying line pressure by the area of the piston, minus any effectiveness lost in transit by an imperfect object such as a flexing caliper.

With power brakes and a 1.124" master, you should get about 600-800psi when really standing on the pedal. If you have a small scale, it should translate to about 100 lbs of foot pedal force.
This ought to put the 2.75" piston output at about 4000#s. With the squeeze of a caliper, this might double... not sure... makes my head hurt thinking about it. Let us know your #s.

[David Pozzi]

I got a spare bleeder screw, drilled a hole straight thru the center, then brazed it onto a 1/8" pipe fitting, screwed a 3000 psi rated grease gun hose on it and ran it to a T fitting with a gage and needle valve on the end. I bleed the hose assy with the needle valve and read line pressures. I've got two of these setups to read front and rear at the same time.