If you are looking at buying a new bike ahead of next season and have been visiting some bike shops in search of your new steed, you will have noticed that many bikes come in disc and non disc brake versions. Disc brakes use two brake pads to pinch a disc rotor that is affixed to the wheels of your bike, one on the front and one on the rear. In this respect they work like rim brakes, by creating friction that slows the wheel, however the big difference is that they are pinching disc rotors and not the rims of the wheel.
So what are the advantages of disc brakes? Let’s take an objective look at the benefits.
Improve performance in the wet
People talk about disc brakes having “more power”, which suggests they probably didn’t have their rim brakes set up correctly, it’s perfectly possible to lock up your front or rear brakes with rim brakes, but where discs definitely give you more stopping power is in the wet. When you apply rim brake pads to rims in the wet, the first two rotations the wheel makes are simply dispersing water from the rim before the pads bite and start slowing the bike. Even when the rims are cleared of water braking performance is vastly reduced, which can be the difference between keeping it rubber side down or ending up under a tree, or even worse, a car. Disc brakes achieve this improved performance by using far more viscous brake pads than rim brake equivalents.
Save on expensive wheels
Wheels are the most expensive upgrade you can buy for your bike. If you’re shelling out four figures on a new set of hoops, you don’t want to have to replace or re-rim them a couple of years down the line because the rims have worn away after thousands of hours of braking. Replacing a disc rotor will cost a maximum of £60 to replace when it wears down, a significant saving compared to replacing your expensive carbon wheels.
Resistant to brake fade
If you encounter long descents when riding, disc brakes can help keep you safe, especially if you are a nervous or inexperienced descender. Some descents can last the best part of an hour, and the novice rider may find themselves riding the brakes for the majority of this time as they speed towards hairpins and sheer drops. Doing so will keep you safe in the short term, but using rim brakes like this will result in temperature building in your rims. There are three problems with this, braking performance decreases, tubes are prone to exploding due to the build up of heat, and carbon rims can be damaged. With disc brakes the only problem you need to worry about is a reduction in braking performance, which they don’t suffer nearly as badly as rim brakes, especially high end disc rotors which provide improved heat dissipation. This means you can sit on your brakes for much longer before you notice a fall off in performance.
However there are some downsides to running discs as well
Risk of bending rotors
If you crash in a very specific way or your bike is not properly handled during transit, there is a possibility your rotor can become bent out of shape and cause brake rub as a result. However such crashes are rare and rotor covers are available to buy to protect your bike in transit.
Sharp edge hazard
Anyone who follows professional cycling will be aware of the controversy surrounding disk brakes. The UCI (international governing body for cycling) ran a trial on disc brakes in the pro peloton. During one race, a rider got caught up in a crash and ended up with a gash on his leg, which he blamed on a disc brake rotor. There is no evidence the cut was caused by a disc brake rotor, however the UCI suspended the trial following the incident, before introducing them again following a review. The jury is out on just how much of a hazard rotors present as there are no confirmed incidents of a rider being injured by a disc brake rotor, but the risk is almost nonexistent in non draft legal triathlon where we have to maintain a minimum distance between us and the rider in front. I’d wager far more accidents have been prevented by reliable braking in the wet that will ever be caused by disc brake rotors. Nonetheless certain governing bodies (including France and Spain) have got cold feet about disc brakes and are currently not permitting them in their events, so it’s worth checking the race information for your event before you make a purchase.
This is a problem for many riders who already have a garage full of wheels, your disc brake bike will not be compatible with any of your current wheels. This means you will have to restart your wheel collection if you make the switch to discs, a costly endeavour indeed.
For the weight weenies or aero obsessives out there, yes disc brakes weigh marginally more and are slightly less aerodynamic than standard rim brakes, but the differences really are tiny, and any time lost due to this penalty can be made up again with improved confidence when braking. Bear in mind that one of the world’s most advanced triathlon bikes, The Cervelo P5X, is only available with disc brakes, and if it’s good enough for the world’s greatest IRONMAN athletes, it’s good enough for me.
Cervelo P5X, possibly the world’s most advanced triathlon bike, available only with disc brakes (image credit Cervelo)
On balance I believe that disc brakes are a superior product and are the way the industry is going to move in the next 5-10 years. There will always be a place for rim brakes due to their simplicity and the fact we’ve been running rim brakes for as long as anyone can remember, but it’s already come to the point where some bikes such as the P5X, are disc brake only.
If you spend a lot of time around road cyclists and have bought up the possibility of switching to disc brakes, there’s a good chance at least one of them will have tried to talk you out of it, even if they don’t seem to have much of an argument against them. The truth is that roadies are very resistant to change, they’re a superstitious bunch who have probably been riding rim brakes for 30 years and don’t see the need to change. If they are comfortable riding rim brakes, I’m certainly not going to try to change their minds, people should run whatever they feel comfortable riding. However you are not a road cyclist, you are a triathlete, and we’re looking for outright performance over tradition and romanticism.
My next bike will be a disc brake bike, as I believe the pros outweigh the cons, however it is a personal decision and comes down to your personal circumstance. If you are an experienced racer who is perfectly in tune with their rim brakes and their limits, then it probably isn’t worth the reinvestment for you, however if you are new to the world of road cycling and looking for your first bike, I strongly recommend you consider disc brakes.