weird brake problem, somebody help me figure this out

[cdlong]

ok, i'm redoing my brakes and i've got a problem in the rear. here's what i've done so far. new hawk HPS pads, brembo rotors, new calipers from autozone (brackets not included). the sliders are all fine and the slide shims were in good shape.

here's the problem. the outer pad isn't making full contact with the rotor. the outer portion of the pad is the only part making contact with the rotor, only about 1/2". the inner part isn't touching at all. i know this is the case because the pad is only wearing at the top and the inner part of the rotor still has spots on it from the brake cleaner. the problem is happening on both sides, though much more pronounced on the driver's side. i made some pictures to help explain it.


the red part is where the pad makes contact with the rotor.

my first thought, i installed the pads wrong, inside on the outside, etc. called hawk, not the case. next i thought the shim was causing the pad to shift because it doesn't go the full length of the caliper fingers. pulled the shim off, no change. called a mechanic hawk suggested, he said the old bracket could have been ovalized over the years. that's the only possible thing i can think of right now. though i don't think this is the case because the inner pad is wearing slightly more on the top than the bottom. if it were ovalized the inner pad would be wearing more on the bottom.

anybody got any ideas or experience with a similar problem? i'm lost. thanks

[cdlong]

come on, somebody take a stab at it.

[Bill Roberts]

I have a few ideas...but without taking a few measurements...they are simply guesses...which may not be helpful.

Is the caliper parallel exactly to the rotor?

Is the shim necessary?

Is the piston parallel to the rotor (mating surfaces)

Is the caliper mount bent at all?

Are the cap screws that hold the caliper on allowed to firmly torque all the way down and seat?

RW alighnment should not play a part in this...but is the lower ball joint on the Rear lower A frame in good condition?

That is all I can think of right now.

[Red]

I'll take a stab...

This is what I found on my car when I did my 1st pad change....

Someone had put the pads on the wrong way... Meaning.

You know the little humps on the back of the pad?... If you put it on the wrong side the hump is right under a peace of metal. making it sit like this \

Make sure when you install them that the humps are clear on the back rest part.. (sorry I dont know any tech names for this stuff)

At least thats what was wrong with mine.... Hope this helps.

EDIT: I know you said you calld on this... But thats all I can think of checking.

[cdlong]

Originally posted by Bill Roberts
Is the caliper parallel exactly to the rotor?

i'll check

Originally posted by Bill Roberts
Is the shim necessary?

no, and it's already gone

Originally posted by Bill Roberts
Is the piston parallel to the rotor (mating surfaces)

i would hope so being that they are new, but i'll check that too

Originally posted by Bill Roberts
Is the caliper mount bent at all?

shouldn't be, this problem only popped up when i installed everything else

Originally posted by Bill Roberts
Are the cap screws that hold the caliper on allowed to firmly torque all the way down and seat?

not sure what you mean, the bolts between the caliper and the slide pins? if so, yes. if you mean the bracket bolts, probably

Originally posted by Bill Roberts
RW alighnment should not play a part in this...but is the lower ball joint on the Rear lower A frame in good condition?

i don't think that could cause this, but everything seemed pretty solid when i put in the new shocks.

[cdlong]

Originally posted by Red
You know the little humps on the back of the pad?... If you put it on the wrong side the hump is right under a peace of metal. making it sit like this \

Make sure when you install them that the humps are clear on the back rest part.. (sorry I dont know any tech names for this stuff)

At least thats what was wrong with mine.... Hope this helps.

EDIT: I know you said you calld on this... But thats all I can think of checking.

i know i installed them in the right location, and the bumps are on the bottom of the pad and something is pushing the top of the pad closer to the rotor.

maybe it's a problem with the new calipers. a month or so ago i replaced just the rear pads with cheap pads from autozone and they worked fine. (that's when i found that everything was pretty messed up back there) so the cause of the problem should be either the pads, calipers or rotors, those are the only parts that are different from the old setup.

[ZodiacSR]

Its your caliper's piston. I had this problem once, just twist the piston clockwise a few times and it should fix it.

[cdlong]

Originally posted by ZodiacSR
Its your caliper's piston. I had this problem once, just twist the piston clockwise a few times and it should fix it.

how could that cause it? i twisted the piston all the way back in to get it on the pads, as soon as you step on the brake it slides back out and when you use the parking brake, it spins the adjusting screw out so it would be exactly the same as if i did nothing. i'll give it a shot, but i don't see how that will affect anything.