Road Bikes & Disc Brakes – an Expert View



Road bike brake technology has traditionally focused on slowing your bike by squeezing the rim. It has tended to work OK … not so well in the wet or on long descents, but as the only choice available, we have adapted our riding style accordingly. But for many riders this is not going to be the future as the availability of disc brake technology has made the transition onto a whole range of road bikes. In this short piece we look at what this means for riders, how the technology is going to improve your riding, and who is going to benefit.

Red Kite Cycles – cycling experts you can talk to.


More power & control to hand

It is a simple statement of fact that hydraulic disc brakes are more powerful than rim brakes: that means increased ability to scrub off speed.  But it isn’t just about total amount of stopping power – another great asset of disc braking systems is that they require less effort to apply their stopping force. A road rider with disc brakes doesn’t have to pull so hard on their lever, allowing them more subtle braking adjustments. We call this “braking modulation”, and it can also be translated as “feel”. The disc brake basically feels like it is working super well and that it has power in reserve which can be easily applied with a little more pressure; the rider knows that they are braking within the system’s capability rather than gritting their teeth on a steep downhill and hoping that they will stop (many of us have been there)!

For the novice who is coming fresh to road riding, why wouldn’t you want the best braking technology available? For you, disc brakes are something to be aspired to in your first bike. And then there are more experienced riders who just want the best out of their cycling experience – for them the upgrade to disc is going to enhance their riding for a whole bunch of reasons that we look at below. For the seasoned fast road rider who pushes their self and their bike towards the limit, it is clear that improved braking is going to make them quicker. Braking decisions are going to be taken later on fast descents, while confidence is garnered by the knowledge that you have the ability to scrub off speed and pull up faster than ever before. Disc brakes are going to make Grand Tour descents more of a true racing opportunity for the super-skilled … the most capable riders will brake eye-wateringly hard and late into corners, basically going faster for longer on the straights. These are the riders choosing Trek Emondas and Madones from our stable.

What do discs mean for wheel/tyre technology?

Adding disc brakes to a chassis allows bike designers a liberating moment. No longer is the design of your wheel/tyre combination restrained by the size of a brake calliper reaching over the tyre to squeeze the rims. And the rim can also lose the task of being a braking surface… This opens the door to wider rims, and bigger tyres. We won’t go into the detail here and now, but it is now scientifically established that the skinniest tyre is not necessarily the fastest. Race bikes have grown from 21mm tyres in my youth, past 23mm of the last years into 25mm and now 28mm tyres and beyond. Here are some wheel/tyre headlines:

  • Bigger volume tyres roll faster – 28mm and 32mm tyres are going to become common on fast road bikes.
  • Not having to add a braking surface to a rim means that it can be lighter and exploit better aerodynamic opportunities.
  • Broader rims allow for a better tyre profile (a bit less of a lightbulb shape when you move up to 25mm, 28mm and beyond).
  • You will no-longer be wearing out your rims when you apply the brakes … this means wheels last longer but your hubs are going to do more miles – so keep them serviced.
  • The advent of disc brakes has coincided with the rise and rise of tubeless tyres; whilst banishing punctures, paired with bigger volume tyres this has also really revised how we think about tyre pressures.
  • Road bikes can spawn into whole new categories once you can add tyres up to 50mm and beyond.

Versatility of disc brake bikes

The road disc revolution is opening the door for a whole new parallel universe of bikes. “Versatility” and “ruggedness” are the new bywords for disc chassis design. In previous worlds people rode cyclocross or touring bikes for that rugged versatility, and would have used cantilever brakes (the only thing capable of spanning their 33m tyres); people on those bikes knew that they were basically not really stopping. The cantilever looked like a brake, but that’s about as far as it went. The addition of hydraulic disc brakes, however, is a game changer. When you throw large volume tyres into the mix, road bike platforms can suddenly be adapted to off-road environments – hence the rise of “gravel” bikes.

Gravel bikes are designed to take bigger chunkier tyres and to excel on mixed surfaces. Trek’s Checkpoint is just such a bike that combines disc technology and versatility in an un-matched package. It has unique “Stranglehold” dropouts to further exploit the chassis – you can keep the rear end shorter for swifter on-road handling, but then pull the rear wheel back for increased stability when the going gets tougher.  The Checkpoint is a bike which sits on the cusp between road and off-road, with many choosing the bike as a road alternative for its big tyre performance on our bumpy lanes. Equally, our Bullfinch VX is that disc-ready version of the modern all-rounder; plump tyres combine with great dynamics to produce an absorbing ride on tough surfaces.

If you take road disc to its logical extreme you end up on an adventure bike like the Trek 920… see the photo slider on this page and dare to dream about where such a bike could take you. This is a road bike that runs a 50mm (that’s 2 inches in old money) cross country tyre and is going to be a hoot when combining a touch of road, lanes, and canal paths with some real trail style surfaces. You don’t have to ride around the world on a bike like this for your ultimate thrills, because it has the capacity to open up the countryside much closer to home with a bike-packing trip across the Peaks or the moors of the UK’s south west.

Equally, amongst all of this technological revolution, we have seen the consolidation of endurance bikes in the market-place. Trek’s Domane, with a model like the SL6 Disc, has been an absolute front runner in this and is also participating in the disc brake bonanza. This bike comes as standard with 32mm slick road tyres – yes 32mm – these combine with the chassis to provide unparalleled comfort and grip. The Domane is without doubt pushing the boundaries of what we consider important in design terms in a road bike. It is smooth, it is fast and it takes all-surface versatility and applies it to our British road surfaces which are simply getting rougher. This is the classic road bike re-imagined through disc technology for the world as it really is. For many people this is all the bike they will ever want.

The limits of disc brakes

Overall system weights of disc brake bikes are slightly higher. The disc callipers, the discs themselves and the frame/fork strengthening that go with disc specific designs each add modest amounts to the overall weight of a bike. Is it a game-changer in terms of bike dynamics though? Probably not. However some people are set on riding just the lightest bike possible, and for them it is going to be traditional rim brakes rather than disc systems that appeal. It is therefore possible that their light bike will be a shade faster uphill, but it won’t be quicker down the other side of that mountain; there it is the disc brake rider who will brake later and hold speed for longer.

It is also worth noting that there are both hydraulic disc systems and cable operated systems. And it is fair to say that cable operated systems are not so effective as hydraulic systems. You still get the benefit of big tyres though, which is a big thing in adding to the versatility of your bike. What cable operated discs don’t have is the outright stopping power and the modulation of the superior hydraulic systems. However cable systems do share that all-weather predictability of other disc systems which is a big asset.