But oversize pulley wheels actually offer enough of an advantage in wattage savings that it may be worth sacrificing style. ... So by opening up those angles and making them less sharp, the chain can articulate less than it would when it passes around smaller pulley wheels. Voila! Less friction.

Are oversized pulleys worth it?

'Larger pulley wheels decrease the amount of articulation required from the chain links,' says Ard Kessels, founder of Kogel Bearings. ... Additionally a larger pulley wheel rotates slower than a smaller wheel, reducing bearing speed and therefore bearing friction.

What do oversized pulleys do?

It handles shifting too and it's important to keep the derailleur on the bike when making a sharp right in a crit race, maybe a bit too close to a curb. This is where things get interesting: oversized pulleys mean a longer distance between the center of the pulley and where the chain runs.