Vertically uneven brake pad wear
 

Last weekend I drove a DE at Eagles Canyon Raceway and used a new set of Pagid Orange pads. They did a great job.

After the DE I found two of the front pads had vertically uneven wear: one with 9.2mm remaining on the top and 10.4mm remaining on the bottom; a second pad is 9.1mm top and 10.3mm bottom. Both of these have little bits broken away along the top (narrower) edge. I think the two uneven pads were on the inside but am not 100% for sure. Horizontally the wear is very even with left and right edge about the same.

The car is an 03 base model with 82k miles. Any ideas? Is this something I screwed up when changing the pads or simply a matter of age?

I figure the uneven pads need to be discarded after resolving the problem but with another DE in April I am tempted to use these again and fix the problem in May. I hate to throw away brake pad that still have 2/3 life remaining. These things ain't cheap.

I don't think it's unusual for pads to wear in a taper, in the direction of rotation and radially. The outside circumference of the disc has more swept area then the inner edge of the pad, and has a higher surface speed, leading to more wear towards the outside edge. I can't comment as to whether this is normal for a Boxster, but 1.2mm of taper doesn't seem too bad.
Steve

did you replace the rotors or just change out the pads?

I had something sort of similar occur with more wear on one caliper than another.
There was some suggestion that there might be an impingement on one of the pistons but the tech that replaced that pads said everything worked fine.

One other thought, if you haven't replaced the rotors, there might be that "lip" on the rotor where the material has worn a bit; if the pad size was just a bit bigger, the lip might be affecting the fit of the pad against the rotor? Just a thought..

MikenOH: The rotors are a year old and still have a lot of life remaining. The top of the pad is more worn so I don't think we can blame a lip on the rotor -- that would angle the pad so the bottom wore more.

Stephen: An increase of rotor linear speed from pad top to bottom makes sense but from what I read the pistons should keep the pad flush to the rotor and ensure even radial wear. I did not see a radially uneven wear pattern after other track events.

If only one pad I'd suspect a cocked piston yet it occurred on both the left and right inside pads. Could inadequate brake cooling cause this? Or maybe I just have bad luck and both calipers need to be rebuilt.

The pistons may be keeping the pads flush when the rotor is hot, but I suppose it's possible that the Rotor is thicker at the outside when hot (especially track-day hot with high friction pads).