Or, if you're going to be out for 10,000 miles without opportunity to buy new brake pads, then discs might be the right choice.
Shouldn't that say, "then discs might not
be the right choice"? My reading on disc brakes suggests the pads don't last anywhere near as long as rim-brake pads. Many on the tandem forum said their disc-brake pads only lasted a thousand miles. Even on our tandem with a gross weight of 350 pounds, the mini-V rim brakes are able to lock up even the front
tire, wet or dry
, with a single finger on the lever, and the pads look like they will last 20,000 miles.
I just saw with the superior stopping power of disk brakes, an opportunity to shear spokes. All the stopping action is close to the center of the wheel, and all the load action (aka moment of inertia) is out at the rim
and they stress the frame and fork differently too (closer to the dropouts), requiring a beefier, heavier bike. The disc brakes themselves are heavier too. But again, as to stopping power, see my note about our tandem's rim brakes above.
Under rim braking, there is still a moment being applied to the spokes via the hub due to the inertia of the bicycle.
It's very minimal by comparison though, and there's no torque at the hub itself.
It is a matter of matching the mechanical advantage of the lever to the brake caliper
+1, and having the right compound. Consider it standard practice to use Kool Stop pads to replace whatever pads the brakes come with. You'll get better braking and longer rim life.
+1 on the drum brake for descents on the tandem, but it's overkill for most single bikes. Deep-V aluminum black-anodized rims will get rid of the braking heat the best, and the deep V makes for a very strong wheel. The deep V makes for more surface area to get rid of the heat, the aluminum conducts heat three times as well as steel, and the black anodizing increases the emissivity, making it able to radiate more heat without exceeding a given temperature.
The main benefit I see to disc brakes is if you ride in rain a lot, since sand, stuck to the rims by the wetness, is like sandpaper if you have rim brakes, grinding down the rims and shortening their life. It's not a problem though for riders who only occasionally ride in the wet.