(very) Uneven brake pad wear after a track day

[dtfastbear]

My girlfirend and I enjoyed a great day of track driving at Sears Point yesterday thanks to Speed Ventures. These guys put on a super show!

Before heading out for my final session, I noticed a horrific grinding coming from the front-right wheel. I pulled the wheel off and sure enough, the pad material was completely gone - down to metal on metal! I figured I had just worn the pads down completely, as they were just stock pads, even though when I teched the car the night before I had at least 5mm there.

When I pulled off the left front, I was a little shocked to see that the pads seemed to be at 5mm - as I had seen the night before.

The rear pads told the same story - seemingly little wear.

I limped the car home only using the brakes twice. When I was putting the spare tire back into its resting place under the hood, I noticed that my brake reservoir was (ack!!!) completely empty! I had just topped off with ATE super blue the night before.

So, what's going on here? Is there a blockage or stuck caliper that held the right front brake on the whole day? Did heat from this cause the fluid in the reservior to boil out? Do I have a leak somewhere in the system? I had just bled the brake the day before, did I screw something up?

Any ideas are greatly appreciated.

Thanks!

Dean

[jluetjen]

The data suggests a couple of theorys which you could check out:

1) You might have 3 stuck pistons and so the vaporized brake was doing all of the work. Did you notice any pulling while you were braking?

2) Were you trail braking at all? If you were always trail braking into a left hand corner it could produce additional wear on the RF.

3) What is the ventilation situation on the RF versus the LF? If the brake was running hotter, you could end up using more material in that corner. In order confirm this you'll need some brake temperature stickers or paint and apply them to each rotor and caliper.

I suspect that the brake fluid from the master cylinder is all in the RF caliper. As the brakes wear, the fluid moves to the calipers to make up for the lost volume in the pistons.

Those would be my guesses.

[dtfastbear]

John,

Thanks for your input. To answer your questions:

1) No, I didn't notice any pulls to the right under braking or while driving. This very well could be just my lack of "empathy" for the car. It MUST have been pulling somewhat with the pads basically gone on that side.

2) I was not trail braking much at all. Sears is predominantly right turns anyway.

3) Ventilation is the same right to left - at least they aren't very different.

I believe that your first suggestion is indeed the problem. I think either the caliper seized somehow (dust cover worn? heat?) or that one of my brake lines (they are old and rubber) swelled and was acting as a "one way valve" allowing pressure to build on the RF but not releasing it.

I'll post back when I know more. Thanks again for the input!

Dean

[jluetjen]

Dean;
You interpreted my first idea differently then I intended -- but I think you are right! If the RF had sized and didn't retract, you could also burn through the pad in no-time.

[radcon]

Not common, but the friction material could have separated from the backing. I don't know how often it happens on P cars, but I have seen it a couple times on other cars.