DiabloScott

Saluti! So after all that discussion, I think no one here is telling you not to buy that bike just because it has disk brakes. You will probably like them just fine and maybe even learn to love them.

cyccommute 

I've bent wheels and had broken spokes on rim brake equipped bikes and still been able to ride them as well. I've even ridden around 100 miles with a touring load on a broken spoke without completely releasing the rear brake. My point is that a rim brake is more forgiving when it comes to its rotor being bent than a hub mounted disc rotor. Bending a hub mounted disc rotor may not happen all that often but when it does things go south much more quickly because there is less margin for error.

I've never found a rotor on any hub mounted disc brake that didn't need tweaking out of the box...either stock or after market. Size of the rotor doesn't matter either.

On that we can agree. Most of the movement to hub mounted disc on road bikes (and many mountain bikes) is more about sex appeal than actual increased functionality. But that has been the case for many years. A properly tuned cantilever brake is just as good as properly tuned v-brakes which is just as good as a dual pivot road brake which is just as good as a hub mounted disc. I have all those flavors of brakes...some of my bikes even have mixed flavors on the same bike...and they all function just as well as any other brake.

What does that have to do with discs at all?

And, again (and again and again) wearing out rims isn't as big an issue as you make it out to be. More rims die due to road damage than to being worn out by braking.

Have you ever done the calculations to see what kind of heat load you'd have to generate to blow a tire off a bicycle rim? I have. If you have a tire at 100 psi at room temperature and assume a blow off pressure of 160 psi, it takes a temperature of 196 C (385 F) to reach that pressure. The temperature needed is lower for tires at a higher pressure but still substantial. Either way, you have to be completely clueless as to how brakes work to obtain those kinds of temperatures.

Hypno Toad

It is true, larger margins on rim brakes, but with tens of thousands of miles on my disc brake bikes, I have had zero issues of the rotor bending/wrapping to the point that I can't ride it. I have had to walk bikes with rim brakes after bending a rim.

So, my attitude toward the issue of a bent rotor is basically the same as yours attitude towards over heating rims - it does not concern me at all. I see both of these as extremely rare and not a real issue.

rydabent

People that seem so dead set against disc brakes remind me of old auto mechanics that hated the idea of fuel injection. They thot carburetors would go on forever. So many people are so set in their ways and wont accept anything new for a long time. They are the type that hang onto their old CRT TVs.

cyccommute 

I'm not "dead set against" them. I just don't see them as an improvement. Fuel injection is an improvement over carburetion. LED technology is an improvement over cathode ray tubes. To pull this back into bicycling, hub mounted disc brakes are lateral move, not an upgrade. In my experience, they don't work any better than dual pivot, cantilever or v-brake. The only reason that they are better than u-brakes is because u-brakes...which were supposed to be the "answer" to everyone's braking problems...is because they are mounted in a better spot.

Honestly, I'm not opposed to improvements in bicycle technology but they have to be a true improvement or have enough advantage to make their disadvantages worthwhile. Threadless headsets, cartridge bearing hubs and bottom brackets and headsets, front suspension on mountain bikes, rear suspension on mountain bikes if it's designed properly, LED lights if they are cheap enough and bright enough, STI shifters, index shifting, external bottom brackets, aluminum frames, carbon forks (perhaps a carbon frame someday), etc. are examples of true improvements that make the bike handle better or is easier to work on or reduce maintenance.

Hub mounted disc brakes, mechanical or hydraulic, just don't fall into the same region as the above. I have hub mounted disc brakes. I have 3 mountain bikes equipped with them...one hydraulic, one mechanical and one with a hub mounted disc and a linear brake. I have 6 other bikes with cantilever (3) and linear (1) and dual pivot (2). I change back and forth between the bikes all the time and not one of them performs any more poorly than the mechanical discs bikes and all of them are better than the damned hydraulic. That one is digital...on or off and nothing in between.

I also help people work on their brakes at my local co-op. My brakes of all flavors are of higher quality than many I see there. I've seen some really poor rim brakes and some really poor hub mounted discs. A poor rim brake can usually be tuned to make it an acceptable brake. Poor discs are just bad to the bone. There's not a lot you can do to make one work properly. Owners of bad discs brakes would be better off Flintstoning.

DiabloScott

And yet, people with rim brakes do have blowouts from poor braking technique on long hot descents with some degree of regularity. Especially heavier people or tandems or loaded tourers and especially on hot days. All that heat in the rim affects more than just the air pressure too. This is truly one of the advantages of disks.

Happened to me only once, and I learned my lesson; but I see people every summer have this happen on the local mountain.

Latif

I have one bike with BB7s,a Salsa Vaya and a steel Seven w/ultegra rim brakes. I take exception to the above generalization. I worked building construction for over 30 years and worked my hands hard and I have a difficult time on long descents on our less than perfect local roads with my Ultegra rim brakes. the Salsa is much easier on my hands because they(my hands) are small and perhaps although strong, worn out. For whatever reason I get very little rear stopping power with the few rim brake bikes I've had but excellent stopping with little effort with my disk rear unit on my Salsa.

cyccommute 

I live, and ride, in the mountains. I'm not light, I've ridden tandems in the mountains, I ride mountain bikes with rim brakes in the mountains and I do loaded touring in the mountains..even mountains in the eastern US which have nastier steeper roads than our mountain out west. I've never had it occur at all on any bike in any situation. I don't recall having ever heard I anyone say that they had blown out a tire due to braking in person nor have I read anyone posting about the problem on the BikeForums. And we discuss every bit of minutia about bikes in elaborate detail here. If it happened "with some degree of regularity" or even rarely, I'd think we'd have as many threads about it as we do about chain lube, disc brakes and helmets.

Not that I've read every post to every thread when you do a search for "blowout" but, of the first 25 threads, none of them seem to be related to brake induced overheating of rims. I'm not saying that it doesn't happen but it appears to me to be extremely rare.

DiabloScott

So we agree that if someone (for whatever unusual reason) were concerned about blowouts from rim braking, disk brakes would be a sensible option. Excellent.


Sheldon's article on it by Jobst: Blowouts and Sudden Flats by Jobst Brandt

It certainly is kind of a beginner mistake... at least a beginner to long hot descents. I see it a few times a year; generally people are sort of dragging their rear brake constantly to control speed and never give the rim a chance to cool off. Could also well be that the tire and tube weren't perfectly installed, could also be that they started with pressure too high to begin with... lots of reasons can contribute.

When it happened to me it blew like a cannon, made a welt in my calf from the explosion, and the rim was so hot it burned my hand when I went to change the tire. Next time I'm in Denver I'll buy you a beer and tell you my story in person and then you'll have n=1.

HillRider

Fuel injection has demonstrable and quantitative advantages over carburetors including better fuel mileage, much reduced emissions (actually the biggest factor), better durability and much reduced altitude sensitivity. The mechanics were intimidated by the complexity but the consumer found it an obvious advantage. The disc vs rim brake debate has no such clear advantage on either side.

cs1

+1

79pmooney

I'm in no hurry to change. I ride in rainy, gritty Portland. Yes, rim brakes kill the aluminum rims I ride in two winters. But having multiple wheels with whatever for hubs and changing them a lot between 5 bikes is no big deal. All front wheels work in all 5 bikes. All the rear wheels work in all the bikes of that spacing.

And those rims that die? I just get another, tape it to the first, swap the spokes over and true. Brand new wheel. $60and three hours.

Murphy predicts that our brakes will fail and need attention at the worst possible times. Jury rigging caliper brakes to get home, even over long distances, even in the dark or rain or snow is almost always doable. I have yet to ever walk or have to settle for a ride for a caliper brake issue over almost 200,000 miles.

Ben

cyccommute 

Not at all. If you are worried about blowouts, it would be better to learn proper braking technique. People may think that they can heat steel rotors to the point where they turn blue without problems but that leads to rotor warping. I've seen pictures of aluminum rotors that have been melted due to the heat. That's not a good thing.

rydabent

hill

But disc brakes do have two great advantages. The do not wear out rims. And rims that run disc brakes can be designed for better strength, weight and aero advantages.

HillRider

Man, I do admire your persistence in bringing up this single and over-emphasized argument. Single note symphony indeed.

cafzali

Honestly, how many people do you know who do this? Perhaps they need to pick another hobby because they're not comfortable enough with the risks inherent in riding down hills/slopes or whatever you have where you live. I'm not the lightest guy on the planet, live in foothills of the Catskills where I'm regularly descending grades of 10 percent and I am still on the original set of brake pads that came on my 2011 TCR.

I think people who are wanting to reinvent the wheel to have discs on road bikes for the most part would be better served by taking a class on bike handling skills.

rydabent

hill

Single note?? Actually I count 2 there, and I could all more reasons if you want me to.

Well-----------why not one more at least, as mentioned, you can ride a disc brake equipt bike with a bent rim.

cyccommute 

Have you really looked at a hub mounted disc brake? There is not much gain in aerodynamic advantages. The caliper isn't all that aerodynamic although it is tucked behind the fork blade. The rotor itself usually has many holes to increase the surface area because it has to shed heat and all of those holes act it increase drag. A rim brake has to shed heat as well but it has a larger surface area and a deeper heat well to do that.

You can find rims of all kinds of strengths independent of what kind of brake you use. It hardly matters. People are under the mistaken impression that a "strong" rim makes for a strong wheel. You can make a rim out of steel and the wheel won't be any "stronger". Spokes make the wheel strong. Rims are just a convenient place to attach the spokes.

A "stronger" rim and a "lighter" rim are generally two opposing and competing goals. Also any weight savings you could gain on the rims is lost to the need for a heavier frame to take the stresses of hub mounted disc brake.

HillRider

Ok, the second note (lighter rims) is just as misleading as the first about wearing out rims excessively. As to riding with a bent rim, caliper brakes can be opened to allow a significantly out-of true wheel to be ridden and a badly bent rims isn't going to be rideable no matter where the brakes are. If the rim is bent that far, it's going to let the tire hit the stays.

fietsbob

`Øne note Samba, even has more than one note .. https://www.youtube.com/watch?v=JDzWWmscbt8

cyccommute 

As has been pointed out to him enough times to become a One Note Symphony of its own

rydabent

The aero advantage I am talking about is the rim. Without having to have a brake area, the rim can be made more aero.

BTW one note?? I bet that in 5 years that almost all high quality bikes will have disc brakes.

HillRider

You're right. Enough is enough.