joewein
Maximum Pace
- Oct 25, 2011
- 3,532
- 3,693
I'll go rim brakes. Mainly because of cost. But I also like the simplicity and the elegance of them for my first proper bike.
To me the difference is mostly about riding in the rain. On dry tarmac, well maintained disc and rim brakes will stop equally well. On a wet road it's no contest, discs win hands down. The higher pressure of the piston against the rotor necessitated by the small rotor vs. rim brake surface diameter pushes water out of the way easily, whereas the pads on a rim brake may need a full rotation to wipe the rims dry enough for action. It could be the difference between crashing into the guy in front of you or being safe.
A second difference is that all rim brakes are wire operated whereas disc brakes give you a choice of wire or hydraulic operation. Hydraulic brakes take much less effort, which can make a huge difference on a long descent in wet and cold conditions (Norikura anyone?). A major reason why hydraulic brakes need less lever force is that any wire needs a spring at the other end to pull the wire back when you release the brake: Wires work much better for pulling than pushing, so the wire will be pulled both ways. That's why when you apply the brakes, your hands not only provide the pressure that squeezes the pads against the brake track but also the force that compresses the return spring. Hydraulic fluid doesn't need any return springs, it flows as easily one way as the other.
With disc brakes you can use really light weight carbon rims, without the risk of overheating carbon clincher rims on long & steep descents.
With rim brakes, your rims will wear out. After several 10,000s of km you will need new wheels or at least have the wheels rebuilt with the old hubs and new rims. With disc brakes, well built wheels should last forever, unless you have major accidents!
If you break a spoke on a disc brake wheel, the rim may start wobbling, but the brakes will still work. On a rim brake it's a major problem.
The above factors favour disc brakes.
OTOH, it's much easier to see how worn a rim brake pad is, compared to a disc brake pad which is much slimmer and sits inside the brake caliper. It's also much easier to change them. You'll probably spend less money on rim brake pads than on disc brake pads and rotors over a given period of time. If you have trouble seeing how many fractions of a mm of pad wear you've got left on your disc brake, next thing you know your brake may not be working at all while you're trying to descend some mountain. If your eyesight is too poor to figure out when the pad is nearly gone, it may be safest to replace pads by how many 1000 km or months you've been riding since the last change.
Most cable operated disc brakes need regular adjustments, far more so than rim brakes. Hydraulic disc brakes don't. They just keep on working well, ride after ride, until they don't (when the pads are worn out). With cable operated disc brakes, get used to learning to use your hex keys to do the adjustments after some wear.
If you even slightly bend a rotor, say when you've been leaning the bike against something, you'll get brake rub. It can be tricky to get rid of again.
Disc brakes can get noisy, especially when oil from the chain contaminates the rotor in the rain.
Rim brakes have a slight weight advantage, but weight on bikes is overrated anyway, compared to weight of riders
Reinstalling a wheel, say after you fixed a puncture, is slightly more complex with disc brakes as the rotor needs to slide back into the caliper. With hydraulic disc brakes you must never push the brake levers with the wheel removed and no spacer inserted into the empty caliper (Shimano provides plastic spacers).
For me personally, the benefits of disc brakes while riding in the rain outweigh everything else. I'm very happy with my Shimano hydraulic brakes. I do not skip chances to ride just because I can't guarantee 100% that it will stay dry. When I sign up for a brevet, it could be months before the ride, when I have no idea what the weather will be like on the day. On a 20, 27 or 40 hour ride the weather can always change. I've done a 300 km brevet where it was raining for the first 150 km.
Both of my bikes now use disc brakes, but other people have different priorities.