ultrazenith":3ofsng6v said:
For XC, which my own particular breed of retrogrouch calls the proper mountain-biking, I'd be surprised if disc brakes made a rider noticeably faster than cantis. For XC, I wouldn't be surprised if the extra weight of discs might even counterbalance the split seconds gained due to marginally later braking.
So, what sort of XC is it that you do? Bimblecore?
The benefit in discs is NOT the ultimate power, its the repeatability, everytime you hit the levers, the caliper does the same thing, rain and mud makes so little difference (effectively none at all) that you only have to worry about traction, which as pointed out up there ^^^^^ somewhere, is noticeably better today than 15 years ago. Chances of buckling a disc enough to make a difference to the repeatability is pretty low. With rim brakes, you have rain, mud (fairly often), buckling (once or twice a race season?), wearing out of the pads, i have on occasion gone through a set of canti or v-brake pads in a single race before. Braking performance changes with pad wear, enough to be worrying. Bedded in disc pads work the same, until they wear out (Which takes far far longer than rubber/plastic pads). Unless you glaze or cook them........
TBH, the modulation on the latest and greatest disc brakes is right up there with the best cantis, if not better. So in XC terms, you are likely to do less damage, as you can pile on the braking loads without locking up. (On hardpack anyway, grassland will be a different matter altogether!)
I'd be very surprised if the weight difference is even noticeable anymore, now that frames/forks/wheels have had all v-brake/canti compatibility designed out. Skinny stays, no inserts in the forks, no hangers, no need for a braking surface on the rim.
One telling thing is that until about 5 years ago a couple of the older, front running WC XC riders were still using V-Brakes, now the courses are a bit more "spectator friendly" i.e. shorter and more technical, everyone is on discs.