Thrust bearings operating in tractant Small radius to contact for input or output High "spin" (Delta V) percentage Brute force control Multiple members changing position Complex surfaces on parts Misalignment affects on load distribution Overloading at different ratios Slow response to torque changes Complex controls Cantilever bending loads Separate oil pump for clamping forces Separate oil pump for ratio control Reversal of rotation direction Fighting between power members Limiting centrifugal forces Limits on size of power from engine High capacity bearings for clamping forces Costly bearings Operation with excessive clamping forces Slippage damage