Disc Brakes on Road Bikes

I was chatting to a neighbour recently when he noticed the disc brakes on my winter bike. He’s a commissaire for British Cycling, who have recently announced that discs will be permitted at British domestic road racing events for the 2018 season, so he was interested to discuss this “new” technology. It was also a hot topic for conversation on our club ride this weekend. So here’s my take.

Much of the debate surrounding discs in the racing peloton revolves around the safety aspects of their use. Broadly speaking there are two areas of concern, the disc rotor causing cuts to riders and the difference in deceleration performance between those using them and those using a traditional rim brake.

The argument surrounding the first point has been the focus of much of the (very heated) debate. World Tour level teams have been getting involved in the discussion, most notably Movistar’s Francisco Ventoso following injuries sustained at the 2016 Paris-Roubaix race, which he attributed to another riders rotor. However, many other teams and their mechanics have responded, downplaying the risks with videos of rotors being stopped using hands and various vegetables without damage (to hand or foodstuff). I’ve not crashed (nor indeed raced) in a peloton, but I do find it difficult to see how, in such a rushed chaotic moment, injuries can be pinpointed upon a single part of a bike and not the various other sharp/pointy/sticky-out components.

Rear end of a bicycle
Sorry, which bit of all this was it that cut you?

The second point, regarding differences in braking performance, is maybe a bit clearer. This once again can be broken down into two situations. In a racing scenario, on a descent for example, if a rider in front is utilising a more powerful braking mechanism and the rider behind does not see the approaching bend whilst judging their braking on the rider in front, there is the possibility that they will not be able to slow in time. Maybe they should pay more attention you may say, but I can see it is as a foreseeable incident.

Secondly, in an emergency situation (a crash further up the peloton for example), having riders decelerating at various rates in close proximity could increase the risk of secondary accidents. In the case of dry roads with a good surface, some have suggested that there is not as large a difference in performance as we may think. In poor conditions, however, the difference is noticeable and the fears of performance disparity become more prevalent.

What about outside the racing world? For a long time, for some unknown reason, I regarded disc brakes on road bikes with disdain. Looking back I really don’t understand why. I had been riding a mountain bike with them for years and would definitely not swap those for anything else. After commuting in all weathers on a road bike with long-drop caliper brakes, I found myself yearning for a more powerful and controllable set of stoppers, especially around rush-hour traffic or wet descents.

Close up of Shimano disc brakes
Shimano Tiagra level BR-RS405 Disc Brake Calipers

Having now ridden Shimano’s fine Tiagra level hydraulic road disc brakes in a variety of conditions and surfaces, my personal experience is that, on a dry day and in comparison to a good quality short-drop caliper rim brake, the difference is negligible, yes there is a difference, but it is small.

However, throw some moisture and other road detritus into the equation, or make the comparison to a long drop caliper, and suddenly the rotors have turned and the disc brakes clearly out perform their rim-braked counterparts. Of course long-drop caliper brakes are not as powerful as short-drop calipers (so says physics), but if you are buying a bike for winter or commuting use, with clearance for mudguards, chances are it would have long-drops in order to gain that clearance.

Close up of Shimano long drop calliper brakes
Long-drop caliper brakes – plenty of clearance, definitely not plenty of stopping power

The increased power of discs does have downsides, even with a larger contact patch of wider tyres, I have managed to lock a wheel. However, the better modulation given by discs means that a small adjustment to braking pressure soon releases the wheel to rotate again whilst still slowing down, a level of control not matched by a rim-brake. This feel and modulation is confidence inspiring, really inviting you to experiment with your applied braking forces.

Of course there is also a wide variety of performance levels within each technology that should be considered. Hydraulic disc calipers generally outperform cable actuated ones, I say generally as TRP’s cable operated Spyre model regularly get rave reviews with comparisons drawn to some hydraulic models and I’ve also ridden some below-par hydraulic models on mountain bikes. A higher level rim brake will also be far better than cheaper alternatives, for example on my partners bike, the first upgrade was from entry level Tektro calipers to some Shimano 105 calipers, noticeably improving stopping performance and therefore confidence, for only a small outlay.

Close up of TRP Spyre disc brakes
TRP Spyres – Widely regarded as the best cable actuated disc brake calipers available

Overall I won’t be racing to get a new summer bike just to have disc brakes on it, the performance benefit for this type of riding just isn’t clear enough for me. However, to anyone considering the choice between the two for a wet-weather or commuting bike I’d heartily recommend looking at discs. I did and it’s been well worth it. They cover a broad spectrum of budgets, but it’s worth considering that this is the component that will stop you in an emergency situation, money may be better spent here than on loosing 10g from your seatpost.

As for the racing world? It will be interesting to see what the likes of British Cycling and a number of other national groups make of them next season and how long until an injury, once again, is blamed upon them.