Freewheeling: The Road Disc Revolution Is Now

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“As a company, we are not coming out with anything right away, but think back to when disc brakes first came on the scene in mountain biking,” Scott Bikes PR man Adrian Montgomery told me at Sea Otter. “Right away people were going faster with disc brakes because they could brake later and with more consistency. The same thing could certainly be true for road biking. And in my personal opinion, I think the UCI legalizing disc brakes would really be in the best interest of the riders. I think a lot of the crashes you see on high speed descents may be due to rims heating up the glue on tubulars and having them roll off.”

Montgomery’s “safety” angle is perhaps the best argument for road disc. By moving the braking interface away from the rim, you free riders from many of the associated concerns of overheated brakes – primarily when those riders are running carbon wheels in the rain.

Instead of worrying about a hot spot on your carbon rim causing your inner tube to explode, or stressing about wet roads rendering your rim brakes useless, you can relish the fact that heat dissipation at the rim is no longer an issue, and that disc brakes work well wet or dry. And because disc brake rotors are smaller in diameter than wheel rims, disc-brake pads need to squeeze with roughly 1,000 pounds of force before lock-up occurs. Conversely traditional rim brakes need only about 200 pounds of applied force before skidding commences.

This wider “braking window” equates to better braking modulation and more control of braking force. Anyone who’s ridden a disc-brake equipped mountain bike with 180mm or 200mm rotors understands the confidence boost that comes from knowing you can bomb a downhill, but still quickly scrub speed in a safe and controlled manner.

“I rode some of SRAM’s disc stuff throughout last year’s cyclocross season,” explained multi-time U.S. national champ Tim Johnson. “Part of that time was riding hydraulic and it worked great. Going into corners you could brake later, which meant an overall increase in speed. But a lot of people are still skeptical, wondering why they’d need it. Well when you ride it you realize that you don’t just use brakes to lock them up. If you can brake safer, it’s going to improve the quality of your ride.”

About the author: Jason Sumner

An avid cyclist, Jason Sumner has been writing about two-wheeled pursuits of all kinds since 1999. He’s covered the Tour de France, the Olympic Games, and dozens of other international cycling events. He also likes to throw himself into the fray, penning first-person accounts of cycling adventures in British Columbia, Belgium, Brazil, Costa Rica, France, and Peru among many others. Sumner, who joined the RoadBikeReview.com / Mtbr.com staff in January, 2013, has also done extensive gear testing and edited a book on cycling tips. When not writing or riding, the native Coloradoan can be found enjoying the great outdoors with his wife Lisa.


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  • Len says:

    Another solution in search of a problem.

    On-road, discs have always made sense on foul-weather commuter bikes, but that’s about it.

    Despite the fact that the industry is, as ever, amped about ‘up-technologizing’ the road bike so that it can charge us more $$$, most riders I know are not champing at the bit to try road discs. Or hydro braking either.

    • Harley says:

      I’ve been chomping at the bit for road bike disc brakes for over a decade.

      They have superior stopping power in all conditions; lighten the rotating mass of the wheel; stop rim wear; are mainly easier to maintain (imo); free the rim design from needing a pad contact area; etc. There aren’t many good reasons to stick with an inferior braking mechanism.

  • Jimbo99 says:

    Gonna be hillarious ? Changing brake pads is going to be like fixing a motorcycle. Why hydraulic, why not a self adjusting cable, like some clutches on automobiles have ? I can’t see me bleeding brake lines, that brake fluid spurting all over the frame of the bike and floor. This is just sheer genius ?

    • Gillis says:

      Jimbo99, I take it you’ve never owned a mtb with discs as your assumptions are totally off base. Changing pads doesn’t require bleeding. Heck, with modern systems you don’t even need to bleed but once a year or less. I had a older pair of Hayes that I didn’t bleed for over 3 years without any problems.

    • aclinjury says:

      don’t get the brake fluid on those pads or else they won’t brake.

    • jim says:

      nothey do it on MTB bike now. notany harderr unless wheile changing the pads out you grab the levers than u will need to bleed than

  • Abe Froman says:

    “It doesn’t happen often, but on hot days you will see a tire blowing under heavy braking due to the rim heating up.”

    In over 30 years and 250k miles of racing, training, commuting; this has happened to me or someone I know 0 times. Shows me how much of a problem it is. If you are using your brakes so much that it heats up the rim until something fails, I’d the the problem is with the person applying the brakes. You might cause the tube to fail with disc brakes; you will just heat/boil the brake fluid until the lever comes back to the bar and you have no brakes.

    I can see their advantage in wet weather conditions but on a clean dry road, I don’t see them having a significant advantage. Don’t need them or want them and I don’t go out of my way to ride in the rain.

    • Abe Froman says:

      That should be “you might not cause the tube to fail with disc brakes”

    • aclinjury says:

      The pro-disc crowds sure make a big stink about
      1) riding in the rain, when in real life most people avoid the rain, well except if you’re my gramp on his hydrib

      2) high speed descent causing the tire to blowout. Perhaps these folks just are not good bike handler, therefore perhaps they should just ride flat and skip the mountains?

      • Harley says:

        They’ll stop you faster in the dry too. This makes a difference when riding in traffic, around pedestrians on shared bike paths, etc.

  • Aaron says:

    Had a nice rain ride yesterday….discs would have been nice. Living in the Midwest though, with no mountains to speak of, wet performance would be the only benefit in my eyes. And as we previously mentioned, most folks avoid riding in the rain anyway so I can see why so many say it doesn’t matter to them. Now if I lived in a region with big, long descents….yeah, I’d like them.

  • Eric says:

    People tend to forget that you can overheat disc brakes too. The tire may not blow off, but the rotor can warp and really cause some issues.

    • Harley says:

      Yes, but with disc brakes the problem is less severe and more easily dealt with (e.g. you can swap to a larger disc if you’re overheating your smaller one often).

  • Ken says:

    I’ve been riding disk on my MTB (s) for over a decade. I’ve had XTR and Avid. Never had to bleed. Pad replacement is simple. Don’t know what all the fuss is about.

  • TA1200 says:

    As my experiences on my mountain bike show, disc brakes offer important advanges: they work more powerful and are easier to modulate especially in wet conditions and notably with carbon rims, brake power can easely be up- and downgraded with other disc sizes, hydraulic pipes break rarer than brake cables.
    Of course you also get disadvantages wich last less or more on your skills: 3/4-1 lb more weight per bike will slow ambitious climbers, they might cost as much as high end rim brakes (also the pads), not everyone is able to change himself pads nor brake fluid (every couple of years), the question of aerodynamic is a more one.
    The communities are: depending of your behaviour and technic, you may overheat both systems and get a failure, you have to avoid damages on disc and rim surface, brake power and modulation are also affected by quality of brake and pads, the less you and your bike weigh and the more broad-shouldered you are, the less you must brake.
    Heavy climbers will benefy considerious more from the safety advantages than light bikers who rarely leave the flats. Finally I will have to estimate if I would invest more money into this marvelous hobby at next bike change.

  • swami says:

    My ‘cross bike has mechanical discs. It’s heavy, partly because of the braking system. However, it’s most definitely my Swiss army knife. I use it to race cyclocross (I know, heavy). It’s my commuter. It’s my gravel grinder. At one time, it was even my century ride. Do I care that those discs add a pound+? At ‘cross races, sure. If I were uber-competitive, I’d definitely think twice about discs, and mechanicals of course suck (relative to hydraulics) for lots of reasons. BUT at those same ‘cross races, the modulation, the non-issues of mud clearing and wet braking, and sheer braking power/performance are all winners for me. Commuting, (I live in the Pac NW) reliable braking in the rain is a real win. Gravel? 1-finger braking and modulation going over washboard at speed is another win. If I were in the market for another Swiss army knife, I’d do hydraulics in a second – particularly given what today is probably just a 1/2-pound penalty. …but Road? I can see some benefits, but this is a technology that will need to shake out quite a bit and standardize before I’d make that jump. Of course I have a sub-16lbs road bike that I love – I am very much not in the market there. Even if I were? Even after years for exposure to the benefits of discs on a “road” bike, I’d be disinclined. There are times I’m too hot in the corners, and better modulation & braking power would benefit me – but not many. For me, all the other benefits don’t apply to road rides.

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