the only thing i've wondered is when i bought them the tires had a very square profile to them and now they seemed to have rounded out a little. the tires say 5 lbs operating pressure so that's what i've always put in them. if you notice the left tire is slightly more rounded than the right. the right tire actually has 4 lbs in it and im wondering maybe i should just drop the pressure down to 4 for a couple rides and see how it feels in comparison. they are wearing a little fast in the center. other then that, ive gotten a lot of riding out of these tires. i rarely ever have to air them up, usually only if i do some nasty romping through some large rocks. i expect to get a number of years on these tires before considering to buy new rears. now to pair them up nicely with some fronts because im graduating in two weeks and i plan on putting some well deserved miles on this bike.