Not many topics are as controversial when it comes to road bikes as the debate between disc brakes or the more classic rim brake. So, we thought we would touch light on the pro’s and con’s of each.
Disc brakes have been around for many means of transportation for ages, but have taken their time to make their way into road cycling. As a result, many cyclists ask themselves why they might need disc brakes if rim brakes have been serving their purpose up until now. To answer this question, let’s look at an MTB example. Maybe you didn’t need a dropper post on your trail bike, but now that you have it, would you ever go back? Probably not. Something that seemed “alien” at first has now become necessary and truly well accepted.
Many have forgotten that around 20 years ago, folks were questioning disc brakes for Mountain Bikes. These days, you rarely see anything else on the trail. It is not always easy to change, but if it is for the better there is no reason not to do it. Let’s have a look at both systems to see where their strengths and weaknesses lie before forming an opinion.
Disc brakes provide substantially more stopping power than rim brakes. This allows the rider to apply less force to the lever before the bike stops. As a result it decreases muscle fatigue in your hands and implements better control and more safety.
Disc brakes offer significantly better modulation than rim brakes meaning it’s easier to precisely meter out the needed clamping power and travel at the speed you want. With disc brakes it also less likely to lock up your wheels as better modulation helps to flirt with that edge of maximum braking power and locking up your wheel.
Rim brakes are a hugely compromised system in the wet, while disc brakes offer very constant performance in all conditions. Furthermore, the fear of a broken rim or flat tire as a result of the rim overheating on long descents is something of the past with disc brakes. Without having to worry about accommodating a caliper, disc-equipped road bikes can now more easily fit higher-volume tires and wider rims for improved traction on a more diverse mix of terrain. Recent studies have shown that the risk of injury for a rider riding disc brakes is minimal.
Rim brakes are still lighter than disc brakes. A common disc brake frame set is around 120g heavier than the frame set of an equivalent rim brake version. The difference doesn’t have to be that significant as shown with the new Foil disc (45g heavier than the rim brake Foil). Additionally a disc brake group set weights around 200-250g more than rim brakes of the same category.
A disc brake bike was historically considered slightly less aerodynamic than an equivalent rim brake version. Recently launched disc brake bikes including the Foil disc have shown that with an integrated caliper in the frame design disc brakes can even have slightly lower drag over ± 10 degrees yaw than an equivalent rim brake solution. At high negative yaw the rim brake configuration creates slightly lower drag.
Both braking systems require routine maintenance from time to time to provide their optimal braking performance. Replacing brake pads is usually easier and faster for disc brakes as they don’t have to be aligned compared to rim brakes. However, the risk of rubbing brake pads is more likely to occur with disc brakes. The clearance between the rotor and brake pads is minimal and therefore it is recommended to have a thru axle for disc brake bikes to avoid this problem.
The lifespan of disc brake wheels is generally longer than that of rim brake wheels as rims don’t wear out because of friction and overheating. A worn-out rim can create a significant danger if it breaks at speed. This can’t happen on disc brakes as the rims are not used for braking.
Possible future improvements
Wheels will likely change with the move to discs as rims will no longer be used for braking. As a result, clincher rims can be designed more for aerodynamic performance and will get lighter, which will positively affect the acceleration of your bike. Road bikes will get bigger tires. 28-30mm tires can easily get fit on disc brake bikes and provide excellent rolling resistance, better grip and more comfort compared to 23mm or 25mm tires. As disc brakes are still quite new it is expected that there is still some potential to design them in much lighter fashion.
Safety is the biggest advantage of disc brake road bikes. However, disc brakes do not only improve the safety. Sure speed and performance can come from aerodynamics, but it should be noted that efficient braking can also lead to an increase in speed. Therefore it was no surprise to see Romain Kreuziger win Ötztaler 5500, the professional race with the most altitude meters on a disc brake bike (Addict RC disc).
We think it is important to improve the safety of cyclists and this is possible with disc brakes without a compromise on the overall performance of a bike. Better brakes, better acceleration, improved aerodynamic wheels out weights the minimal extra weight of disc brakes.