Sincere thanks for the correction.

I'm mentioning it because people are relating their experience with brake effectiveness and rotor size, etc, without mention of wheel size. Since the thread title is road bikes, yeah, probably most on 700c. Me, I ride totally road, but it's on a 20"/406 folder. I just bought a disc bike (not used yet, not as promised, don't ask). But all other factors being equal, those 160 mm mechanical discs should perform better on 20" than 700c.

This is why I shudder when I see a pickup that has had the suspension hugely lifted so higher C.G., and, enormous tires on the same stock brakes, meaning a) wheel torque overpowering the discs, will take huge pedal force and still may not be able to lock, and b) if they can generate sufficient brake torque, the truck may stand on its nose and flip in a hard stop.