My brother's car is a hardtail slipjoint car. From my understanding, hardtails are fine for smooth tracks. If you race at rough tracks, you may want to look into a suspened car. As far as the slip joints, I think you have to be putting alot of power to the ground to make them work. I've always wondered about the joints. You have metal on metal rubbing. Seems to me like it could wear out in those spots.