Originally Posted by
sstorkel
As usual, I think you're over-stating the fragility of disc brakes. In my experience, it's difficult to bend a 160mm brake disc to the point where it becomes unusable without also causing serious damage to the surrounding components (ex: wheel, fork, frame, rider). The best I've been able to do in my numerous mountain bike crashes, was bend the brake rotor to the point where it rubbed the pads a bit... just like an out-of-true wheel tends to rub against rim brake pads. In both cases, braking performance suffers. Luckily, most bikes have two brakes.
I didn't say that they were fragile. I said that they aren't impervious. The world is a very large place and all kinds of things can happen. I would have thought jamming a 1" diameter stick through the arms of the rotor and threading it through past the hub would have been next to impossible but I've seen it happen. It took the better part of an hour to get it loose and get the rotor functional again. Stuff happens and disc rotors
have to be straighter than rims do for the brakes to function properly. There's not a lot of play in there. And that makes them more delicate, as in you have to be careful about how you treat them, than rim brakes.
The two brake thing works well for rims because the rim caliper opens up. Fork mounted calipers don't. About the only option you'd have if you have a rotor that can't be straightened out is to remove the caliper or the rotor. It's not as simple as just releasing the cable.
I take some issue with your statement "As usual, I think you're over-stating the fragility of disc brakes". It's difficult for something to be 'usual' when this is the first instance of me mentioning it.