Raphael Fang if someone says lighter bikes are faster they lie to you. If so then why people use an almost 9kg TT bike instead of a road bike with tribars? Becos lighter bikes are only fast on a climb. Rotational weight (i.e. the weight of the rim of the wheel) only matters when you accelerate. After you keep a steady speed it doesnt matter. This is why disc wheels are faster in time trial despite they are heavier.