When do you guys change tires? (on your bike) I have a used GP4000 Continental on the front with a little bit of wear left according to the wear indicators and a Bontager Hardcase on the back. I have put about 1500 miles on the used GP Continental (don't know the mileage that was already on it) and the new Bontrager. Is 2000 miles the limit are do ya just run'm 'til they blow. I really hate blow outs in group rides.