Brake Force Question

[JHumphries]

So, I'm confused once again.

Correct me if I'm wrong, but

The master cylinder puts out a certain volume of fluid everytime I step on the brakes. So, if I put a smaller wheel cylinder in the back, that should provide a smaller volume. The same amount of fluid would create a higher pressure on the wheel cylinder.

However on the opposite side of the argument, if I look only at the pressure applied by the master cylinder, then a larger cylinder would generate more pressure mased on more surface are.

Please help if possible. Which argument is correct?

 

[Flexiheep]

pressure and area are the way to think about it, the the force applied to the brake pedal and master cylinder piston create pressure in the fluid. That pressure is transferred thru the fluid to the wheel cylinders and applied to the piston. force is pressure times area, for the same pressure your force increase with an increase in area.

The volume thing adds another dimension to the problem, you are basically taking up the slack in the system by using a volume of fluid to move the brake pads and shoes out/in to the rotors/drums. So volume matters, because a larger diameter wheel cylinder will need more fluid to move the brake shoes out to meet the drum (though the larger wheel cylinder can apply more force to the shoes to create more friction)

Pressure creates the force and volume takes up the slack in the system, so there is a trade off between pedal force and pedal travel in a brake system.

An in depth look at brakes can be read here, pretty long, but if you read it and think about it you should know more than you wanted to know... .

BillaVista brake article