I was riding a stock Vittoria Rubino Pro Slick up front, and a brand new Conti GP4000S on the rear for a few weeks...no problems at all. My bike came stock with the Vittoria's (which have over 4,500 miles on them)...so my DH changed them out to the new Conti's to see how I'd like 'em. Well...the 2nd ride out on the Conti's, I took a direct hit into the front sidewall...put a nice gash in the tire, it was toast...had to throw it in the trash. The only tires we had on hand, were my old Vittoria's, so that is what went on my front. Finally got around to swapping out the rear Conti, back to my old Vittoria's. I didn't care for the Conti GP 4000S at all...I'll probably stick with Vittoria from now on.