Originally Posted by conspiratemus1

The larger pulleys would require the chain to be longer (by the same number of half-links as there are extra teeth on one pulley.). But the amount of chain wrap, the important thing for capacity , is dictated by the straight-line distance between the pulleys, as a previous poster pointed out. It’s the distance back that the lower pulley can move as you shift toward small-small that matters, and this is independent of pulley size.

A derailer that had no pulleys, just pins that chain rode around on, would wrap chain in exactly the same manner that real derailers do. The pulleys are just there to provide a low-friction riding surface for the chain. Now, there may well be mechanical benefits from larger pulleys, sure, but chain wrap isn’t one of them.