There is a good reason for them not getting much coverage, too. Remembering the drums on the front of some of the "Krate" Stingray's from Schwinn, and how Sachs tried to make them stop efficiently. The technology for disks is already present, weight can be overcome as can overheating of a disk.

I watched the gnashing of teeth and wailing about disks on all the dirt bikes back in the early 80's, now you only find a drum brake on a low end kids motorcycle, or one of the multitude of Chinese knock-offs, that show up with different nameplates.

Looking at the new line ups from the manufacturers this year, disks are here and are going to get more and more use/acceptance, whether we like it of not. Luckily, we can always fit the brakes we want and ride as much as we need. That is better than fussing, about what we cannot change, all the time. (not you, BP, not you, at all)

Bill

Oh, I second this. I still remember the countless times in college when my old battery operated lamp failed - which was all the time.
Long live LEDs. Which they do.

About disk brakes. I suspect they will become standard, but I have a perverse pride in being the last person on the planet to adopt new technology...

Agree -- from cost-effective and practical standpoints of most recreational riders. However, many riders just love the feel and visceral satisfaction of higher performing drivetrains, shifters, forks, suspensions, brakes, et al. No offense intended, but you seem to view Discs from a "they're good enough" basis versus the reliability or extra-level of security standpoints; i.e., you don't "expect" to ever need them for your Riding purposes, so why spend the money?

Others might decide to spend the extra money just because they appreciate the superior engineering performance of superior-quality Group-Sets. Although above-average Group-Sets are not needed for most recreational riders, neither is a BMW since a Ford Focus will usually get you there just as efficiently.

No right or wrong; we all make different trade-off decisions. I ride like you (recreationally, socially and for exercise); but I truly admire the riding qualities of a higher-performance Hybrid versus the (very proficient) Comfort bikes I initially thought was what I needed. "Need" isn't always the same as "Want".

75-90% of road riders do not need disc brakes. It is all a marketing ploy. All the roadies I know do not go out in the rain. Why would they purchase a new bike with a system of brakes that puts 2-3 pounds on the bike and negatively affects its aero-dynamics, balance and wheel/tire/tube accessibility?
If you have rim brakes and you have problems stopping, I suggest you plan your rides better, buy better equipment and adjust/maintain/repair your brakes more often. There's really no excuse for not having reliable brakes. If you have disc brakes on your bike, chances are that you just got played by companies who needed to sell new bikes to people who already have bikes.

I do ride in the rain, so my new bike (Cannondale SuprX) has hydro disc for that reason. But my other bike is a Emonda SLR with rim brakes and that's what I put 90% of my miles on.

The right tool for the job means you need more than 1 bike for all conditions.

N+1

Look at it this way. Most everything that combines function ends up being a compromise of both functions. A rim that needs a brake surface is not as strong or aero, or as light as a rim that goes on a disc brake bike.

Separating the functions means the rim will never be worn out, and a worn disc is many times cheaper than a new rim with a rebuild of the wheel.

Yea, but in my experience, a wheel is pretty much done (spokes, hub, etc.) by the time the rim wears out. I've bought many new wheels, but never because the rim wore out.

I have. When I rode the rim braked mtb in snow and mud the braking surface would wear through until a low spot would start thumping.

Oh, I don't question the value for MTB applications. Have you ever run through a road wheel that way?

I think the reason they'd prefer disc brakes is because they are generally superior for MTB applications, and they'd rather design, build, sell, and maintain only one brake type.

You know, I hear this all the time, as though nothing unexpected ever happens to ordinary riders; as though cars and other riders and dogs and road conditions are always predictable. Those of us who ride in traffic, especially in urban and suburban areas, can't always "plan" when we're going to have emergency brake to save our lives. It's actually not about being a pro or racer.

Thing is, disc brakes require less time and effort and hand strength to reach full effective braking force in all conditions due to the fact that the pads sit .5mm or less away from the rotors, whereas rim brake pads sit farther--usually much, much farther--away from the rims, and can take milliseconds longer to begin to "grab". (Hydraulics also respond much quicker than cables.) This may not seem like a lot, but at speed, in an emergency, those milliseconds could be the difference between a close call and death or injury. Additionally, disc brakes are much easier to modulate than rim brakes--at least hydraulics are--allowing incredible precision in applying just the right amount of braking force.

Happens, naturally, that I have a story regarding this very thing: the quicker reaction time of discs in saving my life. Bombing down a steep hill, doing something under 30mph, some ******* decided to U-turn, with no signal, right in front of me. Say less than 50'. With disc brakes, I was able to feather and hold the brakes right at the point before they locked. My tires were *literally* squealing on the pavement. I stopped so close that I had to turn my front wheel to the right so as not to hit it against the side of his car. I was close enough to reach out and pound on his roof with my fist as I yelled curses at him. ONE FOOT--That little initial millisecond it takes the rim brakes on my other bike to activate and grab--would have resulted in me hitting his car and flying over, and being very badly injured. This one experience convinced me of the complete superiority of disc brakes--between the stopping power and the fast response and ability to finely modulate the deceleration. I, personally, will never ride anything else again.

It doesn't seem like a lot because it isn't a lot ... completely overwhelmed by other things that influence stopping distance.

I just got off the phone with a buddy of mine who crashed on his tandem this weekend. And knowing the road he was descending (very, very steep and winding), it could have been much, much worse. How did he crash? His brake failed ... a disc brake.

He's a pretty competent mechanic, but had someone else working on his brakes for him, because like any disc brake, they're not as simple as rim brakes to adjust and figure out. So one could argue that at the heart of the matter, his crash would not have happened but for the disc brakes.

I'm not raising this because I think that disc brakes are any more of less prone to failure than rim brakes. I also know someone who had his carbon rim delaminate going down another nasty descent ... and that wouldn't have happened with a disc brake (the rim brake contributed to the rapid failure of the wheel). And tire failures are a possibility with rim brakes if the pads are not adjusted properly. Seen that too.

But anecdotes are just anecdotes. And there are a lot of factors that go into how well you can stop at any given time, and the risk of failure.

I would use discs on a tandem or on an MTB, because IMHO, their advantages outweigh the disadvantages in those applications. Not so much a road bike. If they can figure out a way to modulate fore/aft braking power (easier with a hydraulic disc system, I would think), I might be convinced otherwise.

Unless you commute year round. And don't like to replace worn out rims. ( 4 so far)

Disc brakes certainly offer some advantages over mechanical rim brakes, but as a mechanical engineer, I disagree with your conclusions that the time and effort required to reach full braking force are less for hydraulics. Hydraulics don't respond instantaneously: even though hydraulic fluid is not (appreciably) compressible, the rubber seals in the pistons are compressible, and so are the brake lines. There is indeed a certain amount of "slack", for lack of a better word, to be taken up in the master cylinder as well as the disc brake caliper pistons before full pressure is reached. I'd say that "slack" is pretty comparable to the slack in a rim-brake cable system.

Furthermore, regarding the disc brake pads sitting closer to the disc than rim pads from the rims, note that the rim brakes don't need near as much mechanical advantage: the brake clamping force on a rim brake is sitting out on the rim, whereas the disc brake pads are operating very close to the wheel's axle. For a given stopping torque required, recall Torque= force times distance. Say the wheel needs 100 ft-lbs of torque to brake it to the desired braking torque, and the brake pads are sitting 1 foot from the center of the axle on a rim-braked bike; the brake pads require 100 lbs of clamping force (divided by the pad's coefficient of friction, let's assume it's a generous 1 to make the numbers even). But if the brake is a disc brake, and the disc is only 6 inches in diameter (3 inch radius), then the brake clamping force required would be 400 lbs (if the brake pad is the same theoretical coefficient of friction of 1). So the mechanical advantage of the disc system must be 4 times the MA of the rim brake system to get the same stopping torque. Now, even though the pad sits 0.5 mm from the brake rotor, the disc brake will move inward at 1/4 the speed (or distance) of a comparable rim brake system for the same brake lever "squeeze". In other words, if the mechanical advantage of the disc brake must be 4 times the MA of the rim brake, a 0.5 mm movement of disc brake pad would be equivalent to a 2 mm movement of the rim brake.

So by the time everything is taken into consideration, I'd realistically call it a wash as far as reaction time or lever effort for one system versus the other. The wheel needs a certain braking torque regardless of the brake system used, and the brake lever only has a given amount of distance available for travel inwards regardless of the brake system used--the same amount of work is available at the brake lever regardless of the system, no more or less.

Again, disc brakes have their advantages, as well as some disadvantages, so I'm not dismissing them; rather, just pointing out the real-world dynamics of the brake systems.

I like them just fine on my MTB. I tried them on a mid-level Trek, Domane 3.0 I think, and the extra weight on the wheel made the bike feel sluggish and heavy. Funny how the other trend in roads bikes is lighter & more aero bikes, I guess brakes don't count!

I have Ultegra calipers on my road bike, they work great. On my fixed gears, though, I could sometimes use better braking because I live on a steep hill, and have to ride the brake and back pedal to stay at a safe speed and stop.

I used to set my rim brake pads a considerable distance from the rim. Upon the advice of a couple of BF posters, I tried the opposite strategy: pads set very closely to the rims. I'd estimate pads are now 1 to 1.5 mm from the rim front and back.

I have my own story as well. I was "bombing" down a moderate descent at about 35 mph. I noticed a car pulling out onto the road. I instinctively grabbed the brakes, but had to let go almost instantaneously. The instantaneous bite really shocked me. I wasn't just scrubbing speed, the brakes were biting very hard.

Fortunately, the car didn't pull into the road at all, and I continued on without any further issue, but if need be, I could have come to a stop very quickly.

Dual pivots, even cheap no-name dual pivots like mine ("axis") can bit very hard if you set the pads close to the rim. You need to run and keep your rims true, but it's totally false that dual pivots work slowly or don't bite hard.

I don't think anyone is suggesting that you should NEVER use discs or that discs don't have any useful applications. The question is whether or not it should be forced upon ALL road bikes, in ALL conditions, wet or dry, lightweight vs heavy riders, flatland riders vs riders who ride lots of hills, etc.

On "higher end" bikes, in reality 105 bikes and above, disc brakes are increasingly standard equipment. This adds weight, cost, and exacts an aero penalty and may or may not improve braking power significantly.

That's gotta depend on where you live and what the conditions are like. I commute year round, and haven't replaced one yet ... not even close. Do you commute a lot in the rain?

To me, this photo best explains the push to disk brakes. It's the dashboard of a Yaris. Why do they have the binnacle in the center of the dashboard? It's not because it's functionally a better place to put it. It's because by putting it there, Toyota can make one dashboard for all of their cars worldwide. That not only saves on development and production costs, it saves on parts, distribution, and all kinds of other logistics.



I don't think there is any question that disc brakes are superior for some applications. The bike/component companies would like to standardize them across all applications because they can focus their development solely on that technology and reap some logistical benefits as well. Those development/logistical issues can be huge.

And mountain bikes.

I do understand the point of discussing the issues in terms of physics and mechanical engineering, and attempting to quantify what I experience as the quicker response of disc brake, but somehow these points, whatever their merit, are not taking into account some variable or another that explains why, subjectively perhaps, disc brakes feel to some people, such as myself, more responsive and more controllable than rim brakes; superior in every way when it comes to the actual act of reducing speed. I've been riding rim brakes all my life, and the first time I tried hydraulic brakes, the difference was so impossibly vast there was no going back. YMMV, but to me there is simply no comparison, and though you appear to do a very good job of quantifying all the variables, it's clear to me, experientially, you've missed something. Feels a bit like using math and materials science to show how a wal-mart huffy is as good as a... (Pick whatever bike you think is appropriate.) you can dazzle dazzle the numbers, sure, but in the end it misses something. Something enormous.

Q: have you ever ridden a hydraulic- brake bike?

Yes, well, but the thing with disc breaks is they don't grab. The friction is applied smoothly and linearly and controllably in a way no rim brake bike I have ever ridden can match. Night and day. I've never felt a rim brake that was this absolutely linear and controllable.

Disc brakes are pretty simple to work on, especially if you've worked on automotive brakes. More complex than rim brakes, sure, but not much.

Yes, I have ridden disc brakes, they were certainly very good. I'm not knocking them.

What may be "missing" ....well not really "missing" but rather "unaccounted for" .... Often when comparing new stuff to old stuff, the old stuff isn't in the greatest of conditions. So if the old rim brakes have ancient, dried-out, hard-as-rocks pads, with old stretched cables that haven't been lubed in years, riding on dirty/greasy rims, and is out of adjustment, while the new disc brakes have fresh soft pads on clean discs, then gee the new stuff will naturally seem to be a vast improvement. Conversely, if a brand-new rim brake system, properly set up, is compared to a disc brake setup that has water-saturated brake fluid, hard pads, and oil-contaminated discs, the rim brake should come out on top as well.

So a true comparison would be two brand new systems, on similar bikes, similar tires, similar brake pads, etc. The hydraulic system will have a slightly different feel probably. But if full tire lock-up is achieved at say 90% of brake lever travel with a brake lever pull of 30 lbs on the rim brake, and the full tire lock-up is also achieved at 90% of brake lever travel on the hydraulic system, then the brake lever pull on the hydraulic must also be 30 lbs. Both systems do the same amount of work, they cannot add any power, merely transfer force at some ratio. Both systems, if properly designed, implemented, and maintained, operate at very high levels of efficiency. That can be a big IF in the case of some rim brake designs, I totally recognize that it's easy to wind up with a poorly adjusted, poorly performing rim brake system.

I dunno man ... IMHO, hydraulic disc brakes are substantially more complex than rim brakes.

Maybe that's part of my problem. One of the things I love about bikes is that the embody the KISS philosophy. They are minimalist, elegant devices that are gloriously (and deceptively) simple ... and marvelously efficient because of it. For me to buy into the disc brakes (or electronic shifting, for that matter), they would have to offer a significant improvement for the kind of riding I do. At this point, they simply don't. At least not yet.

You need to get out more, Bill. Quality cycling drum brakes have been around since at least the WWI time frame, and are alive and well, thank you.

All weather, low maintenance, powerful, robust and about as foolproof as you can get: that's why almost every bike share bike has drum brakes!

I agree with you completely about electronic shifting. To me it seems unnecessary and gilding the Lilly, as it were. (I'm not actually a big fan of the newest whiz-bang gadgets, despite my love of disc brakes.) as a matter of fact, the very day I was test-riding bikes and tried my first disc-equipped bike, I tried some electronic shifting bikes. After I got over pushing the lever so hard I nearly broke it, I wasn't at all impressed or intrigued. Ultegra works like magic, anyway. That was not the case with the disc bike! I came flying around the corner of the LBS parking lot, saw a huge manhole cover, and braked hard...and that was it. I literally stopped and stared at the bike in shock because I had never felt braking that was so powerful and smooth...and I was a convert. Disc brakes are a HUGE functional improvement, in my experience and opinion.

Anyway, yes, KISS. But this reminds me of conversations I've had with people about musical instruments, where they don't seem to fully understand how hideously complex a machine a piano is because they're used to it and it's existed forever. Hydraulic braking is a LOT simpler than a derrailer. It has about 4 moving parts, depending on how and what you count, and in terms of keeping it adjusted and running smoothly they are in many ways easier than rim brakes. (You don't ever really have to adjust hydraulics because they adjust themselves.) lots of people love fixies for their simplicity, but, you know, that's taking it all a bit too far.