Go disc or go home?

After the testing this year, the subject of disc brakes on road bikes is hotting up. Team Sky tried it at the Eneco Tour and Trek Factory Racing used them at the Vuelta a Espana. Both seemed to perform well an despite initial fears of disparate braking power within the peloton there were no accidents.

So where are we on the debate? No further forward for those outside the pro circuit actually.

For the pros, the proof of concept has been delivered. There were no crashes because of some riders using discs while others were on rim brakes which was a major concern. Performance seemed to be strong throughout and while no adverse weather or crashes have yet to hit pro riders, they appeared to perform well from what we saw.

Advantages of disc brakes on road bikes

The reason for this debate is the perceived benefits of disc brakes. I use a set of Shimano XT hydraulic discs on my mountain bike and love them. I used standard rim brakes on my road bike and they are fine too.

Advantages include:

  • Strong, definite braking
  • Ability to modulate power depending on circumstances
  • Lower rim wear and more options for carbon rims
  • Better braking in adverse weather, especially the wet
  • Better heat dissipation

All of those advantages can offer a lot to road riders, yet buy a good set of brake blocks and you can have almost the same braking force. Modulation I think is overrated as roadies don’t need the kind of brake control that mountain bikers do. I certainly don’t anyway.

The one distinct advantage of disc brakes over rim brakes is all-weather ability. Even the best brake blocks suffer in the wet whereas discs get better. So for UK riding, disc brakes could make sense.

Disadvantages of disc brakes on road bikes

With every evolution of technology comes a price. Disc brakes aren’t the holy grail of cycling and do have their downsides.

Disadvantages include:

  • No mounting standard as yet
  • Through axle or standard skewer?
  • Extra weight
  • More stress on fork
  • More work to service
  • They can glaze

As with any new technology, the manufacturers come up with their own solutions to practical problems. In the case of discs, it’s mounting and axles. There is currently no standard for either, so different bike manufactures use different solutions. Some use thru axles while others use standard skewers.

Forks have to be made stronger to cope with more stress and the discs, mount and calliper are heavier than rim brakes too. While this isn’t an issue for most of us, it will put some off. There can be problems mounting mudguards to disc bikes too.

Fitting and aligning a disc wheel is trickier and doing it in a hurry can be a challenge. This could be even more apparent if manufacturers adopt thru axle.

One thing that affects mountain bikers but hasn’t been mentioned in this debate is glazing. Disc brake pads have to take a lot of heat and while dissipation is very good, you can overheat the pad. This results in glazing, where the material heats, melts and goes glassy. This compromises braking force and makes brakes squeal. Does anyone know if this happens on road discs?

I’m on the fence right now. My bike is only six months old so I’m not in a position to upgrade just yet. However, even if I were, I think I would wait until a clear winner in terms of mount and axle standard was announced so my choices wouldn’t be limited.


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