On a single seat 1400 lb. offroad race car what do you think would be a good brake pedal force to lock up the wheels.  Its a two master cylindar system with no power assist.  I was using a coeficient of friction of .8 assuming dry asphalt, which would be the highest friction situation this car would experience.

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Sure, most people could manage 50Kg in an emergency easily enough. But you would not design your braking system to require that much force as the "normal" design pedal pressure to slow the car before every corner.

There is a broad compromise between being over sensitive, and fatigue after perhaps hundreds of sequential brake applications on a demanding circuit.

The frictional coefficients of both the tires and the brake material will both vary over a range that cannot always be precisely known. But some basis, and a few assumptions for engineering a braking system from scratch, would have to be better than none at all.

You could even use an old master cylinder in the actual car chassis with the actual seat and pedal, then screw a pressure gauge onto the MC, plug any other ports, bleed the system and have the actual driver apply and reapply thr brake to the maximum level he can maintain at say every 10 seconds for a hour. Calculate force from line pressure.

If possible reduce results by 20% to correct for driver putting in extra effort to "pass" the test. It will end up a compromise between pedal force and pedal travel.

I expect a driver will adapt to lighter pressure easier than heavier pressure at the levels required for a disk brake unboosted system.

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2011-02-12

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