harris - the new rear hubs tend to free the back end of the car up a bit especially on lower speed tighter corners. They work well on both foam and rubber tires from my experience. Sometimes, the Losi XXX-s car with the older style hubs wanted to drift out wide when you are accelerating out of a corner. The new O/S hubs also seems to reduce this as well. They are however still an option as the original hubs still work well and may better suit certain setup or traction situations.