lionman said:
It is difficult to argue that rims brakes are generally better than discs. They may be better suited to some specific scenarios but the reason why they are taking over is that they perform better in most situations.
This seems to be based on a view often promoted in classical free market economics. I know, I've promoted that kind of view myself. But the reality is that the simple fact that some item takes over some market or niche is certainly not strong evidence that is is the better performing item. The reality is that there can and usually are many other factors at work. Buyers in markets are often wildly irrational. And this is especially true when there are not huge and obvious differences in the performance of the items. The better "mousetrap" does not always win.
What is striking about this brake discussion is the degree of insistence and surety from so many people in the face of almost non-existent objective (well done measurements and studies) evidence. Nobody here presented good evidence on stopping power. I would love to see an objective study using a variety of brakes, a variety of bikes and tires, and a variety of riders. But I've looked and found none (though I found one that is sorta close but 14 years old). My bet (based significantly on the results from that one study)is that the biggest differences will be caused by differences in rider skill.
But no bike manufacturers seem motivated to do such a study. I wonder why? And no consumer safety group seems motivated to do that kind of study. Why not? My guess (other than it being expensive) is that manufacturers don't because they know the differences are generally small and that isn't good marketing fodder. They've done enough internal testing to be sure that their products are "safe" and that's good enuf. And consumer product safety folks don't, because bike brakes of the various kinds typically work well enough for the recreational purposes that 90% or more (made up internet statistic) of bikes are used for. They don't see a problem to solve or an agenda to feed. But those are just my guesses. I don't really know either.
My experience is that any good brake system can be made to work well enough for uses on roads at speeds 30mph and below. And from that standpoint, most people buying used bikes for electrification need not worry a whole lot about the kind of brake system the bike has. Any of them can be brought up to a good enough level of operation. [ I did that decades ago with my 16" wheel folding department store Dahon that I'd "hotrodded" with taller gearing (it can burst over 30mph and cruise at typical road bike speeds). New (but not expensive) Weinmann side pull calipers, extra heavy duty (I think 2mm) brake cable and housing from mountain bikes, some heavy duty mountain bike alloy levers, and Aztec brake pads. It could stop fast enough to be scary on that short little frame. Of course, I never objectively compare its stopping distance to my road bike. Who does?] But modifications and parts replacement costs money. So the condition of the brake system is probably more important that the type of brake system from a cost standpoint.
Now someone might complain that settling for "good enough" is sub-optimal and weak. Well, absent some good testing data, I don't know how you can settle for anything else ... cuz you just don't have the data to know with any high certainty. You are left making your own experienced based , biased, and highly subjective best guess and/or the experiences, biases and guesses from others.
