Originally Posted by
Maelochs
Interestingly, the conditions where discs offer the best stopping advantage of rims---corners on very wet descents--are also the conditions where the tires are most likely to give way.
I find that on my road bike, using rim brakes, doing hard stops from top speed i can modulate the rear brake a little to keep it from locking up----or rather, feather it a little so it unlocks immediately after locking, a few times a sa rule ... but that is a panic stop from top speed.
I am not convinced that discs are going to be all that much more easy to modulate at high speed, fighting gravity ... In the Wet, when the braking limit is so low already. Maybe. i am not a road racer so I cannot say.
In the dry, rim brakes seem to be the equivalent of discs.
This is only one scenario and while it's the most relevant for pro racing, it's also just one of the many possibilities for the average non pro rider. Rim brakes can lose all braking power in certain conditions. If the brake tract freezes with underchilled water for example it means that the brake onset delay is several seconds and while that is happening the bike has zero braking power. It's happened to me more than once and it's not a fun situation. Then there's the whole wearing down a structural component part. If one rides in the sunny California it's not nearly as bad as someplace where the ground composition is gravel sandy but there's also moderate to high rain. I've managed to get noticeable wear on a rim in just a few gravel rides.
Other advantages I see and have experienced with discs are
1) Easier and better braking.
The endo limit was discussed earlier. It's a valid argument in a way. However one can endo with a spoon brake with enough grip strength, and a spoon brake doesn't wear down a structural component of the bicycle. Still spoon brakes haven't been used in probably a hunder years as better brake tech appeared, which made braking easier, made it require less effort and allowed for more modulation. I'm talking about rim brakes of course. Rim brakes have advanced of course, but to me the disc brake is an even bigger advancement to rim brakes as it allows for more accurate braking, requires less effort and less strength. Probably the most powerful stoppers I've ever tried have been Vee brakes with really long arms, but they are not at all accurate as the modulation curve is extremely steep and the brakes are very grabby. The road rim brakes I've tried are then the opposite as the low end braking is accurate but it starts requiring a lot of strength to get the full braking power, so one could say the modulation curve is very shallow. In the disc brakes I have the modulation curve is usually very predictable and wide so there's a lot of room for accurate braking but the power increases with very little effort. My mech discs have a fairly long lever travel which is what I prefer as it allows for more accuracy.
2) Allows for better combining of different sized tires, fenders, or even wheel sizes. With disc brakes a 700c bike with slightly narrow tires can be easily converted to 650b with much larger tires.
3) Better lever compatability. One can quite easily disagree with this but at least to me it's easier to deal with disc brakes as a disc frame allows for the use of both long pull and short pull disc calipers as well as hydraulics. One is not as limited in terms of levers as any lever can use a disc brake. However with rim brake frames if you have canti studs you are really limited to either the worst brake on the market now (canti) or you must get used to a massive amount of fiddling (mini vee).
4) discs don't wear down a structural component. Of course those who have never seen a rim wear down don't really appreciate this but where I live it happens quite frequently.
To me they are just overall a much better system in every possible way.