rx7tt95

I have a set of AP 5200 4-pot calipers and have been using Hawk HP pads in them. After hearing a severe grinding noise coming from the left front, I drove home and pulled the wheel after seeing a half inch wide groove in the middle of my rotor, running the full radius.

Once I removed the wheel, I noticed that the outboard pad was nearly gone, with plenty of life left on the inboard pad. Inspecting the passenger's side, it was similar, with a bit more life left in the outboard pad. The driver's outboard was worn to the point that there was no center groove dividing the pad in half whereas the passenger's side outboard had a bit of a groove. Both inboards looked great.

Is the above normal or do I have some sort of mechanical issue at work here? Possible air in the lines? Partially seized caliper?

I swapped in a set of Hawk race pads (noisy!) which I had lying around until a set of Porterfield R4S pads arrive in two days. The good news is that brake pad replacement takes about 1/2 hour for the fronts. If you were pushed, one could easily do it in 10 minutes.

With the brakes being less than a year old, I can't see this being normal. I haven't attended any track events since the brake installation (what a waste). At this rate, I"ll be replacing rotors once a year and pads twice a year. Anyway, thanks for the feedback.
Michel
Michel

DomFD3S

Hey Michel,

Do you have the N-Tech kit? While I do not have actual experience w/ the kit, this is my best guess:

1) You have a seized caliper....as you mentioned.
2) While the rotor does fit the caliper in terms of size, the actual fitment/position is slightly off. Basically as you said, the outboard pads are coming in contact w/ the rotor WAY too early.

I don't think it is air in the system, but you can bleed the system anyway. Brake fluid is cheap.

I'll check my AP Racing catalog tonight.

rx7tt95

Thanks Dom. Yeah it's the N-Tech kit. No word back from them as of yet. I can't imagine BOTH calipers being seized and since they haven't seen much track time at all, I'd lean towards the alignment/fitment.
Michel

rx7tt95

Oh, forgot to mention (duh) I was able to press the pistons back into the calipers without much effort. Seemed to slide back into the caliper smoothly.
Michel

maxcooper

Michel, I have the same kit (13", 4-pot) I think, and I am pretty sure my pads are wearing evenly. I have swapped the pads a few times and I don't recall seeing any uneven wear. I did have SS pistons installed some time back, but I am pretty sure they were wearing evenly with the stock pistons, too. If you end up needing some replacement pistons, shoot me a PM.

Could the less-worn pads have gotten hung up in the caliper somehow? Maybe blocked by the anti-rattle clip or something? Are your mounting brackets straight? Is the rotor in the middle of the caliper?

-Max

rx7tt95

I'm checking the caliper clearance on either side of the rotor in the next two days. Nick mentioned that I may need to shim the brackets although he did not need to do this on his car (and I purchased his kit off of his car). It's quite strange because it's similar on both sides. If it were just one side, I'd think something was wrong. Wondering if the hats are of the right dimensions.
michel