Not sure if there's different compounds between the Shelby's and the PP2's. I got 3200 miles on my PP2 rears with very easy street driving, I was trying to make the set last 1 year before swapping them out. I've heard stories of ppl getting 12-15K miles so that's what I was expecting. I picked up a huge bolt in my left rear, at that time the outside groove was completely gone. My fronts were fine...I sold the pair to a guy who tracks his Corvette.