Been running UST for 5 years now and have had great luck with the Hutchinson Barracuda tires but it appears they no longer make the 2.1 UST except for the Airlight version which does not have very tough sidewalls at all. Killed two in the past 6 months. The 2.3 is still a good tire which i run up front but I need a tougher 2.1 UST for the rear.