The system weight of tubular wheels is considerably lighter than the same material in clinchers because of the shape of the rim. I can take 400 grams off my wheels by going from clinchers to tubs, same hubs and same campy rims. Check the Ambrosio website, they have cross sections of rims there and you'll be able to see what I mean. When you want to use deep section wheels, carbon can keep the weight down but Al gets heavy in deep sections, real quick.