Its obvious how brakes clamp down. What forces cause brakes to open up once pedal pressure is released?

thanks.

 

Take yer foot off the pedal! walla! no more pressure! : )

 

no silly man!
what makes the calipers open up? there is no spring or force apparent to make them open up again. why don't the pads just keep on dragging?

 

ok bro..
power brakes are vacuum operated and that vacuum is what makes it so easy to lock up the brakes at 60+ mph..
Once the vacuum is relieved I believe it is replenished via a one way air valve in the brake booster...this vacuum is what helps "suck" the fluid back into the master cylinder..

 

Hold on.. that dont make any sense..
the vacuum is incorporated within the brake booster...
maybe its vacuum pressure that helps take the pressure off the pedal, creating vacuum on the brake fluid system?

feel free to step in any time brake pro's!

 

yea, but the pads are not adherent to the caliper or piston! they just are on slides and guides. what makes them part from the brake surface?

 

If there ain't no pressure, they ain't gonna stay there!

 

The pads always drag on the rotors. The fluid pressure just regulates the force. The master cylinder may suck the piston back in a little, but I'm not really sure.

 

spring tension.. leaf springs hold the calipers open while fluid pressure regulates clamping force.

brake pads do not drag on the rotor at all times. once properly worn, the pad no longer contacts a flat rotor... a warped rotor on the other hand......

 

in the auto repair class i took (the teacher used to race amatuer stock cars), he said that what pulls the piston bakc that fraction of a mm to disengage the brakes is the piston o-ring. when the piston is pushed out, it twists the o-ring, then when the pressure is relieved, the o-ring twists back into it's normal position and pulls the piston back slightly. don't know if this is correct, but he really seemed to have the expirence and knowledge to know what he was talking about.

 

that would be fine except the piston is in no way connnected to the pad. how does it pull it back open if its not connected? thats what I am asking! See what I mean? I know its silly but I want to know.

 

They (the pads) still ride on the rotors, they do not get pulled back. There is always resisitance between the pads and rotors. It's just when you brake, does the pad provide more resistance and thus stops the car.

 

>>They (the pads) still ride on the rotors, they do not get pulled back. <<

Yep. For an experiment, jack up one of your wheels and give it a spin. Better yet, take the tire off and spin the hub. You can hear the pads sliding on the rotors, and even feel a little resistance sometimes.