Why are Disc Brakes better in the Rain? It is generally accepted that disc brakes will offer better performance in the rain on a road bike.
But from reading many articles on the topic of disc vs rim brakes, I have yet to find any explanation of why this is the case.
The biggest issue with braking performance in the wet with rim brakes is that the rims will accumulate water and dirt which needs to be cleared off by the pads before they start to slow the bike properly. But to me it seems that discs should get just as wet and dirty.
So why are disc brakes so much better in the rain?
Discs have a much higher clamping force. For rim brakes, there's usually quite a bit of movement; you can run the brakes with 5mm clearance from the rim and it'll still work fine. With discs, the pads move a much smaller distance, allowing them to use higher leverage ratios. For example, people running hydraulic rim brakes found themselves crushing rims from all the power.
I imagine this allows disc brakes to have more authority while braking. Water isn't capable of forcing itself under the pads due to the high pressure. Discs also heat up more and can run more aggressive pad compositions (because rapidly wearing out an aluminum rim isn't an issue anymore).The best MTB brakes use sintered metallic pads, which still offer crazy power in the wet.