Brake Line Pressure(s)

[Keith Stafford]

Hey, does anyone know the typical peak (fluid) pressures in front and/or rear brake system? K

 

[Tim Kay]

Keith, I'm not sure what would be typical because a lot of variables at play, i.e. M\C size, line size, bias settings, boosters vs non, pedal length, ect. Here are my readings, non-boosted and biased:

Front 7/8" m\c
Front bias med/max 600/1000
Mid bias med/max 500/720
Rear bias med/max 400/600

Rear 1" m\c
Front bias med/max 300/550
Mid bias med/max 350/600
Rear bias med/max 500/700

 

[Dave P]

Keith:
Tim is correct a lot of variables. Years ago when working with our brake dyno on front calipers. 600-700 PSI normal stopping pressure. Bigger the bore Master cylinder less pressure you can push with your leg.

 

[Keith Stafford]

Guys, thanks, I realise it is a bit of a 'how long is a piece of rope' question, I just wanted a feel for whether it was 100s, 1000s or 10,000s PSI. K

 

[Howard Jones]

If you want to play with a calculator here's a good one. I aim for max pressures of about 900-1100 PSI. Use 80lbs of foot pressure, and about 60% front and 40% rear bias as a target to start.

Put in your master cylinder sizes, caliper piston diameters, rotor diameters, and use 6 to 1 for peddle ratio with a pad friction of 4.75. Guess the rest as close as you can. Keep all the "guess" factors the same and change the caliper piston and master cylinder sizes and see what it does to pressures.

Dual Bias Calc.

 

[Keith Stafford]

Thanks Howard. K

 

[John]

Good info Howard, thanks for posting that.