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Disc Brakes for Road Bikes?

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Road Cycling It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle. -- Ernest Hemingway

Disc Brakes for Road Bikes?

Old 03-03-11, 01:37 PM
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rloftus
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Disc Brakes for Road Bikes?

With a couple of really scary descending experiences, I decided to build a disc brake road bike to try and improve my confidence on high speed down hill runs requiring considerable braking. I am happy to say that I now have a bike with powerful braking, and with a smooth and well modulated action at a light touch.

But, what a battle to get the results I wanted. The installation included STI Avid BB7s actuated from Ultegra shifters. Out of the box, with proper and meticulous installation, braking problems and performance seemed to change every day. Of course there was the expected break in cycle where full stopping power builds, but from there, these things had more tricks that a good magician. One day its pulsing, next its squealing, then a shuddering vibration on hard braking. I can tell you that analyzing and dealing with these problems can be a daunting task. You can insure this by reading some of the 600 post threads I finally found dealing with such issues in the mountain bike forums. These poor guys - there you can find suggestions from binding fishing sinkers to calipers to wrapping chainstays with old inner tubes to reduce brake noise.

In my case, I had to change out the factory disc pads and make some brake modifications that I think should be done at the OEM level to help contain performance issues. But in addition, I had to do some custom work that was specific to my frame to solve remaining problems. For road riding, I have no tolerance for noise or lack of completely smooth stopping power, and feel that the benefits of disc braking (to me) were well worth my effort to harness the beast. But, I wonder if a manufacturer could successfully produce a disc brake road bike free of significant individual performance issues, or if disc brake applications will evolve to solve these annoying problems.

I know some of you must be riding disc bikes in road use, and I would sure be interested in your experiences and satisfaction with your braking performance. Have you faced these kinds of issues and what has been your level of success in dealing with them?
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Old 03-03-11, 02:01 PM
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Seattle Forrest
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My cross bike is what most people would recognize as a heavy road bike. It has disc brakes. I miss them when I take my Cervelo out in the rain. I like the consistency of stopping time, eg not having to "wipe" the rims down before they'll really do their job. On the other hand, the bike doesn't handle all that well, and the improved braking becomes something like a crutch. I'm not a good enough mechanic to try and make them work on a really nice bike, so I take one or the other out ... I'm not surprised it was as difficult as you say.

I've been noticing more drop-bars bikes with disc brakes lately.
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Old 03-03-11, 02:05 PM
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I can skid my Ultegra brakes on my road bike instantly... That is all the braking I can get and it really doesn't matter if it's disc or rim. This is of course on a dry road. Wet rims.... then you have a valid argument.

The reason I can't stop faster is the fact that i'm riding on skinny little 23mm tires.
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Old 03-03-11, 02:10 PM
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https://www.bikeradar.com/commuting/g...l-kantor-28944

interesting interview
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Old 03-03-11, 02:17 PM
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I've thought that disc brakes on road bikes have been overdue for a while now. With more and more carbon rims being used by the casual rider I am surprised that I have not seen many yet. Think how much lighter the rims could be made if they didn't have to deal with braking. A very small disc is all that would be needed for a road bike. My tandem has cable actuated disc brakes and they work very well. It could all be downsized quite a bit for a normal bike.
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Old 03-03-11, 02:37 PM
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In my opinion/experience, the short cable pull on road levers makes the Avid Road BB7 particularly tough to set up. Personally, I prefer calipers for dry weather, but in wet stuff, discs rule.
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Old 03-03-11, 02:42 PM
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I converted my CX to disc in the front via a fork swap. My frame unfortunately doesn't have disc mounts in the rear or I may have attempted both. I picked up a carbon disc fork for $175 or so.

For use in conjunction with Ultegra STI levers, at first I tried Avid BB7 Road brakes with stock 160mm rotors and I was absolutely underwhelmed by the performance. Just about as bad as the cantis I had worked so hard to replace. Then I picked up a used BB7 Mountain brake and tried that. Because of the difference in cable pull, the mountain brake should have more clamping force on the rotor, and boy did it ever. Stopping is now extremely powerful, easily modulated. It is the performance I was hoping for. Stopping power between the front and rear is now definitely different, and I've heard some criticize a front-only conversion for this reason, but my feeling is that anyone who rides a bike instantly becomes aware of a difference in stopping power between front and rear. This conversion just requires a little familiarity and then it feels like second nature.

The drawback with this setup is that because of the change in cable pull, while you get more clamping force, you also move the pads less relative to the lever pull. As a result, it is really easy to run out of lever pull while not fully engaging the brake. Getting the brake pads tuned properly, keeping them close to the rotor and keeping the rotor true are all necessary. There is less room for error.

I seem to have had more consistent results than you report...I haven't noticed changing braking force or pulsation in the brakes, but I have definitely had noise issues. And I mean screeching, louder-than-a-train-whistle squealing. The kind of squealing that makes people turn their heads from from across the street. An LBS guy told me to do the following: clean the rotor with brake cleaner, sand the surface with very fine grit sandpaper (I had some 400-grit stuff that I used), then bake the rotors in a 350 degree toaster oven for 10 minutes. Follow up with another quick cleaning with brake cleaner. I did as he recommended, and while I'm not sure of the effectiveness of baking the dang rotors, one or all of those steps seems to have significantly reduced the squealing. I still get some noise, but a lot less.
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Old 03-03-11, 02:52 PM
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Do a search on disc brakes on the thread title only. There are a couple very good threads on the subject.

I recently bought a cross bike that has disc tabs as I wanted a bike to fill a certain purpose which is to ride in the wet (I live in Portland) and be able to decent confidently on the huge decents we have here in the PNW and not take a chance of blowing a tire due to the rim getting too hot from rim brakes. I just did the conversion so I don't have any experience to share yet, but everything I've read from others reports are that the braking is predictable and precise. Which makes me think you have something wrong. Couldn't begin to offer an opinion to what this is, but it doesn't fall in line with other things I've read.
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Old 03-03-11, 03:25 PM
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Originally Posted by krazygl00
I seem to have had more consistent results than you report...I haven't noticed changing braking force or pulsation in the brakes, but I have definitely had noise issues. And I mean screeching, louder-than-a-train-whistle squealing. The kind of squealing that makes people turn their heads from from across the street. An LBS guy told me to do the following: clean the rotor with brake cleaner, sand the surface with very fine grit sandpaper (I had some 400-grit stuff that I used), then bake the rotors in a 350 degree toaster oven for 10 minutes. Follow up with another quick cleaning with brake cleaner. I did as he recommended, and while I'm not sure of the effectiveness of baking the dang rotors, one or all of those steps seems to have significantly reduced the squealing. I still get some noise, but a lot less.
If you are troubled by squeal, you should really, really, really try Kool-Stop organic pads. They do so much for both noise and breaking consistency.

$12.50 at https://www.utahmountainbiking.com/sh...brakepads.html
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Old 03-03-11, 03:27 PM
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I use disc brakes on my road bike. 622mm's too, none of those whimpy 207mm rotors
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Old 03-03-11, 03:32 PM
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Originally Posted by merlinextraligh
I use disc brakes on my road bike. 622mm's too, none of those whimpy 207mm rotors
Ahh, you beat me to it.

This is beating a dead horse.
In order for it to really hit the road market, you will need both brakes plus rotors and mounting hardware to be no more than 250 grams, which is heavier than we have now but thats within the realm of weight penalty for adopters. One argument is you can subtract out the rim weight from lighter rims no longer having to support braking, but I don't think there will be any savings with carbon wheels. Oh but of course a 300 grams carbon fork won't be able to support that torque at the dropouts either so add extra weight there.

The issue for road bikes disc brakes is that they solve a problem that doesn't exist.

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Old 03-03-11, 03:37 PM
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Originally Posted by knobster
be able to decent confidently on the huge decents we have here in the PNW and not take a chance of blowing a tire due to the rim getting too hot from rim brakes.
I could be wrong, but I don't think this is a problem on single bikes, and I don't think the PNW descents are epic enough to be much of a problem anyway.
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Old 03-03-11, 03:54 PM
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Originally Posted by teterider
The issue for road bikes disc brakes is that they solve a problem that doesn't exist.
Not all advancements have to solve a problem. All they have to do is offer some advantage over a previous design and be priced within reason. Right now, that advantage (mostly wet weather performance) comes with a weight penalty. That's a trade-off that just doesn't sell to most road bike customers. Commuter bikes, on the other hand, are adopting disks more rapidly.
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Old 03-03-11, 06:12 PM
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Lance and Levi supposedly want discs for their road bikes:
https://www.cyclingweekly.co.uk/news/...re-choice.html
Earlier today, Lance Armstrong posted on his Twitter feed, "UCI approves disk brakes for cyclo-cross. Great news. I look fwd to the day they're approved for road racing."
https://www.autoweek.com/article/2010...NEWS/101219947
Surely driving fast is less daunting than hurtling down a mountain at 55 mph on thin bicycle tires.

“I think they're very similar,” Leipheimer opines. “You've got to look well ahead and not turn in too early. On the bike, our brakes are pretty good, but we definitely need disc brakes.”
I've also heard that Lance has said that since they're already ballasting race bikes to meet weight regulations, it wouldn't be much of a drawback to relocate that weight to something useful like disc brake setups.

I'm kinda ambivalent about discs on race-ready bikes for myself, but I'm definitely including them in my next commuter build. I've had them on street & road bikes before and they worked as promised, even without sanding & cooking them.
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Old 03-03-11, 06:47 PM
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Originally Posted by Phantoj
I could be wrong, but I don't think this is a problem on single bikes, and I don't think the PNW descents are epic enough to be much of a problem anyway.
Yep, you're wrong. I've done several that are longer than 10 miles and about 4%-7% in grade. Ever heard of Mt. Hood? Crater Lake? Lots of epic climbs here. Not to mention those just North of us in Washington. Mt. Rainier and Mt. St. Helens are two that I can think of. If I want to control my speed, I'd be seriously heating up my wheels with rim brakes. And yes, I've known people that have blown tubes because of wheels that have gotten too hot. This when it was dry. Come try them when it's raining. Yep, we do climbs like this when it's raining... This is where disc brakes really save the day.
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Old 03-03-11, 07:47 PM
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The predictions of disc brakes generally expanding into road and racing use based on performance aspects are interesting to me. I was never disappointed in braking performance with rim brakes, but was instead focused on a perception of safety. I am admittedly and unreasonably paranoid based on a couple of experiences. In the first, I had a front tire blow off the rim on a decent for no apparent reason. I almost rode it out, but finally the tire jammed in the calipers locking the front wheel, and put me OTB, in the road, and unable to pick myself up. The second incident occurred in the South of France descending The most incredible 12 miles of steep hairpin switchbacks. About two thirds down, my front tire instantly deflated but thankfully stayed on the rim. The partial loss of control almost put me over a rock wall, and when stopped, I found the rim too hot to touch. On any 5+ mile decent that demands much braking, there is no way I can get these incidents out of my head, and there is no way I can feel really comfortable with very good performing rim brakes.

Justified or not, my disc brake build is intended to set me free and help me finally enjoy descending more than climbing. As expressed in my original post, I find a good disc braking system pretty finicky to set up, but I find the effort both rewarding and worthwhile. I have no sense of the future, but I did read the interview with the Avid engineer kindly linked above and found it very interesting. Hopefully light disc systems for road bikes will evolve into options worthy of serious consideration in the near future.
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