Originally Posted by
cyccommute
Just to be clear, the wheel that loses traction is the rear wheel. The front wheel can’t skid on a bicycle. The rider will flip over the front wheel before that happens. Rim brakes can easily reach the same limit as any rim mounted disc brake.
I'll assume you mean a bicycle front wheel cannot skid on clean dry tarmac type surfaces whilst riding forward?
Your definition of modulation is correct but it’s not something that I have ever experienced with hydraulics. Hydraulics have always been powerful in my experience but it’s just raw power. Trying to control it in those places where intermediate braking is needed is not easy. Every hydraulic I’ve used has been grabby with control always on the edge of disaster. Mechanical (and rim brakes, for that matter) provide exactly the intermediate control as you describe it.
This is one strange difference in people. I've been quite impressed lately by the control and modulation I get from my hydraulic disc brakes. Takes a bit of fiddling to get the one finger position setup properly but once that's done I'd wager the four piston hydraulic brakes I have on my fatbike are the most precise brake system I've ever ridden. I can do manuals with them, which hasn't ever been possible on any rim brake system or even mechanic disc brakes.
And then on the other side of the coin are vee brakes which are truly on/off with very little modulation in between. Very powerful yes, but also very dangerous as it's just way too easy to lock up the front wheel.
Hint, look at a rim and rim brake caliper. Look at a hub mounted disc and the caliper. Notice something? They are exactly the same. Same principle and very similar mechanism. They only differ in pad material. That is why hub mounted discs are somewhat better (but only somewhat). A rim brake could be made that is just as effective as a hub mounted disc if we were willing to use steel rim and sintered metal pads.
While that might be true the end result could end up being pretty darn bad in general. Steel rims are difficult to manufacture to the complex shapes aluminum rims are extruded to and the resulting rims would likely be less stiff than aluminum rims in all directions especially if one tried to get close to aluminum rim weights. Also I'm not sure steel rim walls would manage without flexing in such a system.
If the wheels wobble, fix the wobble. Hub mounted rotors can just as easily develop a wobble and rub. Removing the wobble is much harder than taking it out of a rim. Spokes are easier to minor adjustments because it’s just a simple tension adjustment. Rotors require bending that is far less precise.
No it's not. Rotor truing is far easier and far less stressful than truing a properly tensioned and properly sealed wheel (sealed as in first lubricated and then thread locked with either a certain type of oil or with actual thread locker). Truing a wobble wheel is even more difficult if it hasn't been lubricated in the first place. Just had the pleasure of truing the machine built wheels of my new bike and it was horrible I tell you.
You also have the distance argument wrong. Rim brakes don’t need to have a huge gap between the rim and the pad. They are often set up with a huge gap between the rim and the pad. Most bikes are adjusted so that the pad doesn’t hit the rim until about the lever has moved about half way to the bar. I don’t care what Sheldon Brown says, that makes for very mushy brakes and what many people experience when they use poorly set up rim brakes.
Probably depends on the brake. With modern calipers you need to set them up with a significant gap or the brake won't work as intended. With mini vees and road levers you need a tiny gap and you'll be adjusting it constantly. With cantilevers again you need a tiny gap to get any kind of power out and even then it's pretty abysmal what you can get. With actual vee brakes and mountain levers a decent gap is again ok. Just before midway is the best place for the brake to actually bite I find.
And here is the reason that many people dislike rim brakes. If the rim brake is set up so that the brake actuates much earlier in the pull, the brakes feel more powerful and the braking feels better. You can detune disc brakes to the same half lever pull and the best hub mounted disc will be the worst brake you have ever used.
My BB7's bite at half pull and I get pretty nice performance from them. I've tried the instant bite too and didn't care for it as it A) makes the bike noisy (now I did say truing rotors is easier than truing wheels but I don't actually bother truing rotors all that often) and B) means I need to then adjust the lever travel as well and that's a hassle. I mean I could do it, but I'm not really sure where the adjuster screw is in my brifters if they even have one... In terms of when a mechanical disc brake bites there's no reason why you'd get any less power with a later bite point if the brake is otherwise setup properly. The most important factor of course is that with a single moving pad system the immobile pad is as close to the rotor as possible. With dual moving pads.. I dunno, I had such a bad time with the Spyre that I've temporarily given up with that.
I think most levers these days even compensate for travel so that's not a reason either.
A well set up rim brake will exert enough braking force to send a rider over the bars. That’s the limit of braking for bicycle under any brake.
I hear that a lot but I don't think it's entirely true in all situations. My townie bike has a modern version of the long arm caliper brake and what pushed me to get a townie bike with disc brakes was an incident where the old bike failed to stop with the front brake in a steep hill. Now mind you, the brake is setup properly with the adjustments which are available to that brake and it even has Kool Stop dual compound pads. Still failed to stop with a fistful of brake lever being grabbed. I've had the same thing happen with cantilevers which then pushed me to sell my cyclocross and get something else instead. And those too were properly adjusted. I know it's tempting to now indicate that clearly said brakes weren't properly adjusted but if I can't manage to adjust a set of brakes properly there's something deeply flawed in that system as it seems to require some arcane knowledge 15 years of wrenching my bikes does not provide. Sure it's possible that I can manage every other wrenching task without breaking a sweat whereas rim brakes are still a total mystery. I've only owned rim brake bikes for 10+ years but sure it's possible. But I think it's unlikely.
Come to think of it, I've never had a situation where I've been even in danger of going over the bars, but I think that's more to do with my weight. And having bikes with long wheelbases. Very rarely do I even lift the rear tire. But the only brakes I've lifted the rear tire with have been disc brakes. No rim brake has ever had the power available to achieve that. Then again, I've never owned an actual road bike with short travel calipers.