Question about my rear brakes...

Does anyone know why the rear pads would wear faster than the fronts?

My situation:

I have a 2007 Touring with now 20k miles. Braided Brake Lines, AP Racing DOT3 Fluid, Factory calipers and rotors, Hawk HPS pads in the front (4k miles) and factory pads in the rear (20k miles).

I inspected all four brakes before I went out, and everything looked fine. I tracked the car this weekend, and after my 4th session my rears went metal to metal.

So my question is (and everyone at the track had the same question)...How in the world did I use up the rears more than the fronts?
Is this a known issue for the 350z or something wrong with my car?

 

Stock pads just aren't up to the task of track duty. I don't recommend running on the track with anything less than a full track pad. I've had good luck with Hawk HT-10's and Ferodo DS3000's so far. Stock pads are inadequate and any street/track pad is just a compromise and certainly not ideal, esp if you're going to push the car hard.