Urban Velo

Ask B Rose – Thoughts On Road Disc Brakes

brose Industry tech legend B Rose is back with another dose of tech opinions. In this column B Rose lets us know his thoughts on mechanical disc brakes on road and cyclorcross bikes. It may not be what you want to hear.

Submit your own questions in the form at the end of the column.

Q:I hear a lot of hub bub about disc brakes on road and cyclocross bikes. People seem to either love it or hate it. What’s the word?

B Rose: The yin and yang of disc brakes; it is not as easy a question as you might think. I love disc brakes on my mountain bike. But there are limits even in love. One thing I can’t abide (get ready to object) is mechanical disc brakes. I know many of you just did a spit and asked, “Who is this joker?” But I have found that mechanical disc brakes have three major flaws (none of which you will admit to). One, they are almost always set up wrong. In all my years specializing in suspension and disc brakes (enough to be way old school) I can count on my fingers all the times someone has put a properly set up set of mechanical disc brakes in front of me.Two, at their worst possible set up, mechanical disc brakes are totally unsafe (it’s a rare situation but I can show you at least 3 examples of ways people roll the dice with their mechanical disc brakes). And finally, and this especially applies to road, touring and cross bikes, they feel like crap. Lets clamp a piece of metal between two more pieces of metal and string a piano wire between them and your hand. Yuck. I hold a pretty high standard and I hate that feeling; it’s bad on a mountain bike but even worse on a road or touring bike (or cyclocross if you are going fast enough). Hydraulic brakes damp the connection and you don’t feel every jerk and ping of the rotor in your lever.

Why did I take you through all that? Because mechanical discs are your main option right now. So for me that is strike one of the “discs on cyclocross” argument.

Strike two? Squeal. Cyclocross, road and touring bikes amplify the biggest issue with disc brakes in two ways. Speed and contamination. I personally feel, with no engineering background, that 700c wheels glaze the current offerings in disc brake pads over very quickly. I say 700c and not 29er because the bikes that refer to their wheel sizes as 700c are faster than your mountain bike or 29er. And contributing to squeal, contamination; you find it so plentifully on pavement. It’s an educated guess that most people use their road, touring and cyclocross bikes on the street. Streets are very oily and that kills disc pads! My favorite bike is now made in a disc version, and everyone I know with one complains about their discs squealing constantly. If your discs squeal until you replace you pads and clean the system then contamination is the issue and that is 100 times more likely on the street.

Strike three? The best thing about about disc 700c bikes is also the third strike for me. Wheel interchangeability. It’s really a terrible reason to do anything on a bike, but it is a total myth with discs. Fits fine, still needs adjusted every swap. Show me a mechanic whose heart doesn’t feel like it is being squeezed every time someone wants to non-permanently swap their disc wheels. So when it comes to swapping out your wheels; you know they are going to need to be readjusted, you know they are probably gonna squeal and in your heart you know the correct answer is just to, “run what you brung.” Wheel swapping is an idealistic idea that always ends in a set of unused wheels.

It’s fashion, and there is nothing wrong with that, but it is the wrong idea. Sorry. Commence fling of slings and arrows now.

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About B Rose

B Rose: Industry tech misfit legend and excellent cook. B Rose has been in the bike industry since 1989 as courier and shop rat, spending half a decade at QBP before running suspension and hydraulic specialist shop Shockspital from 2007-2011. "I have argued over sausage with Sheldon Brown and argued with many more besides, I am immune to marketing and I cry when I watch Monk. I like to think of myself as the biggest outsider of the bicycle insiders and am proud to add my name to the b-list of bicycle celebrities."

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18 Comments

  1. ToddMarch 20, 2013 at 8:35 am

    Hey B.

    If mechanical disc brakes are often set up incorrectly and in an unsafe manner, can you direct us to a source on how to set them up right? Or maybe do a future article here on UV so we’re riding safe?

    Thanks for the article.

    T

  2. JoeMarch 20, 2013 at 9:34 am

    There’s a lot of bad science and opinion in this pos, it’s about the worst article I’ve ever read on here. Poor show urbanvelo.

    Crap brakes are crap brakes. mechanical brakes are cheap and easy to hack together, hence there are more cheap & nasty mechanical systems out there.
    Hydraulic brakes have a major disadvantage in that they suffer from heat much more than mechanical.

    If you set-up brakes badly they won’t work, regardless of disc or not.

    “Hydraulic brakes damp the connection and you don’t feel every jerk and ping of the rotor in your lever.” is just plain wrong and shows a poor understanding of the physics involved. One would even go as far as to ask if the author has ever used a good set of mechanical discs?

    “I personally feel, with no engineering background, that 700c wheels glaze the current offerings in disc brake pads over very quickly”. It’s the riding, not the wheel-size. Appropriate size rotors and heat management in the design is important.
    Most publicized accidents from road discs have been in cases where rotors of insufficient size or design to shed the heat have been used.

    Wheel interchangeability is very, very easy with discs and no set-up, readjustment or faffing is required. if you use the same size and brand rotors on each wheel it’s utterly brainless.
    I cannot believe that this article is the product of anyone with technical awareness at-all

    The only issue that I can see is contamination from sharing an environment with cars – but in 10 years of running mountain-bike discs on the road this has never been an issue, except where I have carelessly put the disc into a puddle of oil whilst changing a flat.

  3. rMarch 20, 2013 at 1:02 pm

    Let’s not forget that a 700c rim and rim brakes are essentially a disc brake. The rim acts as the disc and the pads/brake mechanism are the caliper.

    Properly adjusted rim brakes far out pace disc brakes in non-mountain bike applications. This is evidenced by, longer lasting pads, less brake fade, more stopping power, etc.

    In regards to mechanical disc v. hydraulic: mechanical are sub-standard. They tear through pads and have no compensation for the loss of pad material. This leads to brake levers going all the way to the bar and no braking power.

    None of this is to say they are not people who have set-up disc brakes for their road rides and it works for them. However, it is important to disregard myopia when talking about bike set-ups (they’re as different as the people who ride them).

  4. hellbellyMarch 20, 2013 at 10:58 pm

    B, I am with you 100% on hydros over mechanical disc brakes and agree wholeheartedly in regards to using mechanicals on 700c wheel bikes. One can “get away with it” on mountain bikes, but they feel like shit really fast on road bikes. Personally, I think they suck ass on mountain bikes too, but whatever. I do, nonetheless think that door has been kicked open for discs on road/CX bikes and decent hydros that neither weigh a ton nor are overly complicated are coming. It would seem that it would allow for wheels to be built with even lighter weight rims that could be carbon without the fear of heat/catastrophic failure issues that plague them.

  5. RaiynMarch 20, 2013 at 11:28 pm

    +1 to Joe
    -9000 to B. Rose

    So much fail in one article.

  6. DanMarch 21, 2013 at 12:29 am

    What a crock of shit this is

  7. BenMarch 21, 2013 at 10:01 am

    I’ve been using mechanical disc brakes (BB7) on a road bike for a year with two wheel sets as an experiment prompted by a chat with Brad. Bottom line is that my experience with that setup has been great. I’ve never felt uncomfortable stopping in any weather conditions and maintenance relative to rim brakes during winter has been amazing. Switching trail/road or road/ice wheels has been easy after a bit of care setting up the hubs. Only issue has been squealing and I’ll live with that given the advantages I’ve experienced.

  8. The GoatsMarch 21, 2013 at 10:56 am

    Just an observation and opinion.

    Hydraulic calipers have a general advantage of actuating both pads simultaneously where mechanical generally do not. We are looking forward to seeing how the TRP HyRd hybrids work as they area a wire fed caliper with hydraulic actuation of both pads.

    Road disc calipers like the BB7R do not generally work as well with a regular road pull lever as a set of regular MTB type BB7′s do with a long pull lever like the Tektro RL520.

    Regardless of our opinion on discs we will concede that much of the push for adoption appears to be driven by the advertising departments and not the engineering departments of the big companies.

    XOXO

    The Goats

  9. epicycloMarch 23, 2013 at 8:12 am

    I’m with Joe. Poor article.

    Maybe Mr Rose only sees the bikes of incompetents.

    The only problem with good quality cable disks is if a poor quality outer cable is used. Easily and cheaply fixed.

  10. Matthew JMarch 24, 2013 at 5:36 pm

    In fact the detractors here uderscore the original author’s point.

    Most people who ride bikes have lives that involve things other than bikes.

    Sure, those road cyclists with the time and inclination can pick up the intricacies of hydraulic discs well enough. But why? Quality dual pivot calipers are inexpensive, simple to set up, easy to maintain.

    Most road cyclist swap wheels only at such time as their existing wheels wear out. Been a near daily road rider going on 20 years now. Neither I nor anyone I have ever heard from have suffered from catastrophic rim overheating.

  11. RaiynMarch 24, 2013 at 11:55 pm

    @ Matthew J
    Now you have. > 2 seconds on the google
    http://forum.slowtwitch.com/gforum.cgi?post=3352818;search_string=glass%20transition;

  12. Matthew JMarch 25, 2013 at 2:19 pm

    Yeah, and in > 2 seconds on google I can find a poor picture of a warped disc brake rotor. Have I proven anything?

    The point is not that overheating rims from rim braking does not happen. The point is that overheated rims from rim braking is so infrequent as to not be a significant factor in deciding whether to go rim or disc for 99% of the road riders out there.

    When compared with such factors as cost, easy installation, easy maintenance, lower weight the few overheated rims per millions of miles of that rim brakes work without fail, calipers have a lot going in their favor.

    It makes as much since to deny the point as it does to say people should not use carbon forks because there are internet pictures showing cracked CF.

  13. drinkslingerMarch 25, 2013 at 3:36 pm

    +1 to both joe and r +100 to the goats

    It seems to all be about the marketing.

  14. DanMarch 27, 2013 at 5:13 pm

    90% of the engineering savvy industry folks I’ve heard comment on this issue are bullish on road discs? Wonder why that is?

    It seems like marketing folks (and consumers are eagerly playing along) are driving toward a solution without a problem….a solution (road discs) that has a ton of tradeoffs for very little gain.

  15. BenMarch 29, 2013 at 12:46 pm

    Brakes just slow you down.

  16. Urb AnwriterApril 12, 2013 at 7:10 pm

    Damn! I never knew my brakes were such a bad break. I always figured that having rims left at the end of the year was a good thing. I always figured that being able to fix a flat without fighting with the general grunge and filth that my commuter bike, my load bike, my ‘all around” bike, and my one-speed can accumulate was an advantage.

    Squeal – sounds from the above that it only ever comes from disc brakes. On the other hand, 20+ years spent wrenching, frame-building, retailing never introduced me to ’boutique’ caliper or canti brakes that squealed. Nope. Or the agonizing time spent working on cheap bikes for whom ‘non-squealing’ brakes were the exception.

    And pad life? Hey, I’m over 200 lbs, the bike is 50+, and I’m impressed with pad life. I was never, underline never, impressed with the life of any rim brake pad.

    And then there’s rims. Yes, you could class your caliper or canti, or u-brake (yes, there were at one time more than a few mounted to front forks being used a road bikes, in the daily commuter sense) get great, or not so great, feel. And go through multiple sets of pads in a year, and get a year out of a rim. Oh, the way a rim separates along the brake track is so cool I wish I could make my discs do it. I miss destroying rims by riding on them.

    I’ll leave the separate argument about hydraulic vs cable to other people: I’ll think about juice brakes when everyone standardizes on a fluid, a hose size, terminal fittings, and offers more than one master cylinder diameter/stroke. In the meantime I can, and have had to, adapt long-reach brand ‘crap’ kids brakes to a Surly fork while on tour – cars will do that to you.

    Rim brakes?

    Never again. I’ll stick with my BB5s, BB7, BB7r thanks very much.

  17. RogerApril 16, 2013 at 6:21 pm

    I ride a bike as a commuter 35 miles every day that has BB7′s on it and I love it. I have none of the problems stated above. Maybe I just know how to set up BB7′s? They are also the only brakes I use on my mountain bike. They are easy to fix and cheap. The only time I ever have noise is in light rain. In heavy rain no problem.

  18. Jody HershbineNovember 19, 2013 at 6:27 pm

    I agree with a few of your comments, but on a touring bike I would rather carry a spare brake cable and a pack of Avid pads with me, that I could fix easily on the side of the road, rather than a broken hydraulic line. If you take the time to set them up properly, they work great, and a bent rim isn’t as annoying either…

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