I've been having a problem with flats on my Trek 8.3 ds ever since I got it last September. Doesn't matter that I have liners in them and it doesn't seem to matter where I ride whether it be offroad or on. I always get flats. I mentioned this to some of my friends who are long time cyclists and they basically told me that the problem is the stock tires suck. In fact, one of the flats I got was caused by a pebble we pulled out! So, can anyone suggest some good tires for this bike? Keep in mind that I use it to ride with my roadie friends quite a bit so I don't want any heavy duty mountain bike tires. I want good, strong tires that will let me go fast, but not shred if I hit the trails. Thanks!