Originally Posted by
Rowan
Having just set up a disc brake on the bench... well it was just soooooo easy. The proof will be in the riding, of course.
But a critical factor not really highlighted yet in this discussion is the longevity of rims. Take the pad quality of V and canti brakes. Shimano pads are renowned for being very abrasive on rims. Koolstops have a reputation for being relatively gentle, but I have worn a Velocity Aerohead front wheel to a point of concern.
Most importantly, there are the conditions, and I am not talking about braking efficiency here -- I am talking about if you ride in wet, gritty conditions that will wear away the rim wall rapidly. A (real) advantage of disc brakes is that they rotate away from crud on the road, and are less prone to wear because they don't pick up the grit so much. Plus, you don't have horrible grey masses of fine brake dust oozing all over your rims, tyres, frame and clothing.
I am interested comments from long-term users of both types of brakes as to how long their rotors and their rims last under the respective systems in similar riding conditions.
I am not sure, also, that it is entirely fair to compare the efficiency of either brake by using tandems as the basis. No touring bike is going to be ridden with another person plus luggage on board, as well as the extra mass of the frame. The issues of overheating might be real in very very tortuous conditions, but why do not the same principles of cadence braking (on-off-on-off) apply to disc brakes?
I went with mechanical discs because of their simplicity in set-up and adjustment. I have dealt with hydraulics in other automotive arenas and they can be finickity if (a) your seals aren't totally sealed, (b) everything isn't totally (surgically) clean when servicing and (c) you don't use alcohol to clean the system (there are others, but that's a start). Above all, it's much easier to replace a broken or bent cable than it is to source a new hydraulic hose and the associated paraphenalia to connect it (which also could be read as a positive for rim brakes).
It's also worth pointing out that rim brakes are in fact disc brakes in of themselves.
I can mount and adjust either a set of v-brakes or a set of avid BB-7's in about the same time. Neither is particularly hard and both require some care and knowledge to get the best performance out of them. I've seen poorly adjusted discs and cantis.
Rim life will be better on a disc rim for sure, but what is better and does it matter? For a rainy/winter commuter or a tour through mud or really wet dirt roads I'd lean towards discs as they don't wear out your rims as fast. For just about anything else rim wear has never been a factor. This obviously depends a lot on the rider and situation - I've never been hard on brakes or rims - I can't explain why other people burn through pads/rims so fast???
I've gone through Avid BB-7 pads faster than I have kool stop v-brake pads. Not really a huge deal as both kinds of pads are small and light enough that carrying spares is a non-issue. I've not worn through a rotor yet.
I posted the tandem link as an example of the issues discs face during hard use. There was a German mtb bike magazine article that compared how much heat various braking systems could take before failure. The disc systems failed at around the same heat that rim brakes blew out tubes - unfortunately my link to that article no longer works. The problem with over heating IMO isn't the type of brake, but how it is used. I don't think a normal fully loaded touring bike should have brake overheating issues in the mountains with either rim brakes or disc brakes if used correctly, but I wanted to emphasize you can over heat and essentially destroy your rotor on a disc brake just like you can overheat a rim on a rim brake and blow out a tube.
All my discs are mechanical cable actuated. I don't trust hydraulics for a travel bike and for a bike I use in town I'd just as soon stick with cables as they are easy to work with. You might convince me to use a hydraulic disc for winter commuting. I have an original Avid disc brake - essentially a BB-7 which is 7 years old and going strong. I also have a new set of BB-7s and they both functional identically.