ebaypargon

hi, all.

I have 2nd gen RX7 rear. I am in the middle of install, and stuck. need help:

1. on the back of brake pads, there is a nipple.
2. on the piston, there are 2 notches (this is where caliper retracting tool will sit).

question: does the nipple sit inside the notch ? if so, doesn't the piston suppose to rotate outward ? won't the nipple prevent that ? if you see picture below, my old pad had the nipple sitting in the notch.

if the nipple does not sit in the notch, do I dremel it off ?

btw: my car is a 99 Miata with RX7 rear brakes. thanks all.

Hypertek

iTrader: (3)

the notch is to hold the brake shims

doesnt look like you have them in the pics. You could probably dremel it off if you wanted.

CyberPitz

What's the real point of the shims, anyway? I've never really understood, just kept them on.

Hypertek

iTrader: (3)

i figure to keep the pads from shimming? lol
dont know how a little piece of thin metal could do that. I guess it might be due to heat properties i dont know

ebaypargon

sorry, still a little confused.

not sure what shim u r refering to.

so I should dremel out the little nipple sticking out ?

but doesn't all RX7 brake piston have a notch ? and all brake pads have a nipple ? you guys have to dremel it too ?

does RX7 piston rotate when pushed out ?

sorry for my dumb noob questions.

Hypertek

iTrader: (3)

no just keep it.. the shim im talking about is
see pic
http://www.rx-7source.com/showpics/t..._Torn_Boot.jpg

rotorhead_izzy

iTrader: (36)

when i installed my pads i didn't dremel anything. and yes the piston does rotate out.

ebaypargon

okay, but if you look at my pictures. the nipple/stub is much taller than the shims.

so if the piston does rotate out, won't notch get caught by the nipple/stub ?

by looking at Hypertek's bottom picture. the stub is also taller than the shim. when you guys install it, do you rotate the piston, so the stub/nipple sit just inside the notch ?

and if you look at my top picture, you will see that the stub/nipple do sit against the piston.

thanks.

ebaypargon

anyone ?

CyberPitz

I wouldn't imagine that would cause an issue. But if you're worried, just get rid of it, or shorten it down.

clokker

iTrader: (2)

You'll have to rotate the piston to retract it enough to accept the new, thicker pads anyway.
And yes, the stub/nipple fits into the notch of the piston.

ebaypargon

I went to a mechanic this morning. he confirms the stub/nipple does fit into the notch of the piston. but he doesn't know why you have to rotate the piston to retract it, but it doesn't rotate when it pushes against the pad. : that just didn't make sense.

wrankin

You have to rotate the piston to compress it. That's the way it works on the rears. I believe that this is because of the e-brake, but I'm not 100% sure. The pin on the pad fits into the notch on the piston. It prevents the piston from rotating further once the pads are installed. Make sure the notch lines up with the pad once you have finished compressing (screwing in) the pistons.

It's not rocket science, and it's a pretty standard design - the disk brakes on my Audi sedan are the same way. I'm very surprised your mechanic didn't know this.

-bill

ebaypargon

thanks. but why doesn't the piston rotate when it un-compresses ?

RockLobster

iTrader: (7)

I belive it works with somewhat of a ratcheting effect. That is why you have to rotate it to bottom it out, then back it off some to line up the notch with the nipple.

It is this way because it is part of the e-brake system.

Shims are used with brake pads to:
1) Reduce or eliminate brake noises/sqeal.
2) Even out pad wear on some cars (like our fronts).
3) In some cases reduce heat transmission to the fluid.

RacerXtreme7

iTrader: (2)

No the pistons to not rotate as they uncompress. They simply are pushed out of their bore by hydolic pressure (when you step on the brake pedal) or by mechanical means (e-brake). They only rotate to leave room for new pads. Rotate them till they bottom, then turn them back till they line up wiht the nipple protruding from the pad (YOU DONT CUT THAT OFF!!).

~Mike..................

ebaypargon

thanks all, finish installing. I just wasn't able to picture mechanically how piston rotate to compress, but don't rotate when uncompresses.