I put BT 21's on in the spring, I have 8500kms on the front tire, About 5000 miles. I am going to FLA in two weeks for a course at Jacksonville, I am thinking I'm going to replace the front tire before I go. The back is fine, it has about 4000 Miles on it. I cant believe the front tire is worn out so bad, ( More on the sides) I am a hard front brake user (simply because its the only way to slow down) I Know linked brake system, equal braking ect, this ought to generate some passionate replies lol! If you train yourself to front brake most of the time, when u hard brake in avoidance your brain will tell u to front brake if u panic, long before u think about it. Train ur brain it will save u. Anyhow back on topic. Very disappointed with BT 21, so I think Im going to put on the BT 23 to try it, unfortunately the BT 23 GT is not available in the ST size. So in the end it will be two front tires to the one back tire replacement ratio!