I see that the piston in the caliper twists and has 4 little groves on the circumfrence(sp?) of the piston. There is a little nub on the back of the inner break pad which fits into one of the groves at a time. My question is, as the brake pad wears down, how does it move from one grove to the other with the piston pushing on ti yet not making the inner brake pad wear unevenly.

Also, i'm about to bleed my rear passenger wheel because I just replaced the caliper back there. From what i've read, i need to run some clear tubing from the nipple on the caliper to a container that has brakefluid in it with the end of the tubing submersed in the fluid. Have a friend pump the brakes slowly while i watch for air bubbles. Once there are no more bubble, I retighten the nipple and i'm done? All the while I'm monitoring the brake fluid level under the hood.

 

anyone know?

 

to bleed the brakes, get a tube and a jar and attach the tube to the bleeder valve on the caliper. stick the other end of the tube in the jar, have a bottle of brake fluid handy to keep the master cylinder topped off under the hood. When you loosen the bleeder valve (1/4 turn) have someone depress the brake peddle relatively slowly until down to the floor, then close the bleeder valve. Repeat until the air bubbles are gone or if you have time you should continue until running clear fluid if you want to flush your lines. You should bleed the opposite corner caliper too, because brakes are normally connected diagonally in case one system fails you have one front and one rear brake to stop you. Just make sure you don't run out of fluid under the hood otherwise you will have to bleed every brake all over again.

 

just to clarify more, if you let up on the brake pedal before the valve is closed you will suck air/crappy fluid back into the system

 

oh damn, really. I poured some brakefluid in a cup as used that as my container. I didn't close the valve until I thought it was finished. I never saw any air bubbles going back up through the tubing so I doubt any got sucked it. Shoudlnt' have though cause the tube was submersed in fluid. Now dirty fluid probably did get sucked up. I'll bleed the whole system later once I have someone to spend that much time sitting in my car. thanks

 

"My question is, as the brake pad wears down, how does it move from one grove to the other with the piston pushing on ti yet not making the inner brake pad wear unevenly."

The piston does not rotate as the pads wear thin. Inside the rear caliper the cable brake mechanism has a ratchet like effect that actuates a cam, pushes out the piston, to pick up any gap resulting from pads wearing thinner. This piston push is always out. This is why you have to turn the piston back in the caliper to install new thicker pads. The 4 notches on the piston are meant to allow grabbing the piston for the turning.