Monday, July 6, 2015

Another Take On The Disc Brake

Shimano hydraulic disc brakes for road usage. Courtesy:
Back in 2012, after I noticed a surge in city and road bike models coming out with disc brakes, I offered A Short Take On The Disc Brake describing four situations where disc brakes might be preferable to rim brakes.

Over the last three years, Shimano, SRAM and others have continued to update and redesign brake levers and discs for road use.  For example, in August 2014, Shimano released its ST-RS685 compact hydraulic disc brake levers, which they promoted as providing "more stopping power with less effort."

Not everyone is enthralled by this technological shift toward hydraulic disc brakes.  In a recent exchange with David Hembrow about Trek's District bikes, I suggested that Trek had listened to him in designing the model. He responded:

Mr. Hembrow prefers drum brakes encased in the hub.  As he writes in his blog:

Enclosing the brake and gears leads to extremely high reliability. Neither the gears nor the brakes have required any maintenance, unlike my bike which has rim brakes and has required new brake pads. Not only rim brakes, but disc brakes also are not really low maintenance components. When used in winter, salt on the road causes the disc to rust, and brake pads need replacing fairly regularly. Drum brakes, or Shimano's roller brakes, are much more reliable than this. 

Drums brakes are not widely available in the U.S. bike market, although you frequently see Shimano roller brakes paired with Shimano Nexus hubs.  Still, Mr. Hembrow's point is well taken. Drum brakes work well, especially on flat terrain such as the streets of Amsterdam.  But what about his point about disc brakes? Should we avoid them because they require a higher degree of maintenance?

There are two categories of disc brakes: hydraulic and cable-actuated.  The latter category requires maintenance similar to rim brakes: replace the cables when they start to get stretchy.  My family owns several mountain brakes with disc brakes, and I haven't noticed any problem with rust despite riding on wet, muddy trails. 

Hydraulic brake systems, like those in an automobile, need to be flushed every so often.  John Allen, writing on, cautions that "disc brakes are more complicated, expensive and difficult to maintain than rim brakes or drum brakes."  But he lists a number of advantages of disc brakes as well, including the fact that they allow heat to dissipate without damaging the tire and they don't wear rims.

If disc brakes are a factor in your bike purchase, I highly recommend reading all of John Allen's article on the subject as well as the links at the bottom of his article.


Matt said...

I think brake choice is very dependent on where you ride. Personally, I like having disc brakes (or V-brake style rim brakes) on everything because they provide the best stopping power. Drum brakes or roller brakes may have better longevity, but with where I ride I value the ability to stop quickly more than I value low maintenance. The maintenance itself isn't really that big a deal either... changing out brake pads is something most people can learn to do in a few minutes with youtube videos.

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