A normal tire is a clincher, where the edge of the tire fits insude a U sectioned rim. Racers use tubular tires, also known as "sew ups", where the tire wraps right around the the inner tube and is sewn together on the inside. The tubular tire is mounted on the outside of a box sectioned rim. Tubular tires are lighter than clinchers, and give better handling because 100% of the inflated area is outside the rim. You can also continue riding a tubular after you get a flat, which can make a difference if you get a flat in the last few seconds of the race. Tufo make a tubular that can be mounted on a clincher rim. but I dont know how it compares for weight and handling. I believe some other forum members use them, so they may be able to give more info.