Are you referring to the grooves seen in Van Doorne push type CVTs? If so, the Subaru CVT pulleys have smooth sides and the steel chain pulls, not pushes with no mechanical interlock between the pulleys and chain. Force is transfered between the pulleys and chain by friction alone.After studying the CVT drive Chain/cable/link mechanism with its little traction grooves machined into the 399 keys, my question becomes" How much wear has reduced those little traction grooves, how much life is left in them?" How tough/resilient/wear resistant are they?
My understanding is that the CVT fluid stiffens when under pressure such as when trapped between the cones and chain elements and this increases the friction up to the level required. This is why the the higher torque CVTs for turbo, 6 cylinder and diesel engines use a different fluid to the 2.5i N/As.