This paper presents a tribological model for a toroidal CVT. The model predicts the lubricant film thickness, viscous and boundary generated friction and the spin power loss in the contact. This is in order to evaluate the effect of different parameters on the efficiency and durability of the CVT system. An optimisation study is carried out to ascertain the effect of contact surface materials, lubricant rheology and contact geometry upon power loss and maximum generated contact pressure. The results show that numerically, even if the contact pressure cannot be significantly reduced, the contact spin power loss can be reduced by as much as 24%., thus improving system efficienc
