In recent years, road bike disc brakes have become an increasingly common sight in racing, with Tom Boonen being the first rider to ever win a professional road bike race using disc brakes in 2017.
Yet, their introduction into the sport hasn’t been without objections from many in the industry.
This begs the question: Are road bike disc brakes truly better than rim brakes, and if so, to what extent do they actually improve performance? Or, are they just a new fad and an unnecessary new product that the bike industry wants you to buy?
Like it or not, it’s becoming increasingly clear that disc brakes likely are the way forward for road cycling. However, this doesn’t mean they’re without drawbacks.
To properly answer whether should you be using a road bike with disc brakes, we’ll be covering:
- How Do Road Bike Disc Brakes Work?
- The Debate Around Road Bike Disc Brakes
- Disc Brakes Vs Rim Brakes On Road Bikes
- Mechanical Vs Hydraulic Road Bike Disc Brakes
Ready for the lowdown on road bike disc brakes?
How Do Road Bike Disc Brakes Work?
Disc brakes consist of a metal disc – also known as a rotor – attached to the center of the wheel. When the brakes are applied by the riders, the pads squeeze against this disc, causing friction and slowing the wheel, thereby decelerating the bike.
There are two main activation methods to clamp the pads onto the disc:
- Mechanical (Cable-Actuated) Disc Brakes: A cable runs between the brake levers and the brakes. The brake lever pulls on the cable, which clamps the brake pads onto the disc.
- Hydraulic Disc Brakes: When the brake lever is pulled, fluid is pushed down a narrow hose, pressing the brake pads against the disc. It’s the same braking system used by cars and motorbikes, and generally delivers more powerful braking performance than mechanical disc brakes.
The Debate Around Road Bike Disc Brakes
Disc brakes have traditionally only been used on non-road bikes such as mountain bikes, gravel bikes, and cyclocross bikes.
This is because disc brakes offer much higher braking power, work better in a wider range of conditions, and do not get as easily clogged by debris. However, this is not as important on road bikes, where riders are less likely to be in steep, off-road conditions.
Furthermore, disc brakes are heavier than rim brakes, which has traditionally been a downside on road bikes, where weight is a priority.
However, in more recent years disc brakes have begun to appear on high-end road bikes.
In 2012, SRAM introduced the first disc-specific road bike groupset. Other manufacturers were soon to follow.
In 2016, disc brakes on road bikes were allowed by the UCI in road bike races as part of a trial period. However, the initial uptake of disc brakes by the riders and teams was slow.
In a complete U-turn, the same year, disc brakes on road brakes were then temporarily banned by the UCI after Spanish rider Francisco Ventoso suffered a deep cut on his leg after running into the rear disc of another rider at Paris-Roubaix. Ventoso described the discs as “giant knives”, and many other riders were in support of the decision to ban them.
Many bike manufacturers protested this decision, claiming that this risk to riders was very low, and that disc brakes were in fact safer overall.
These claims were evidenced by the fact that disc brakes offer more braking control over a wider range of conditions. Therefore, in a racing scenario where riders travel at very fast speeds in any weather, the ability to quickly stop when needed is ultimately safer.
Many other riders had been reluctant to use road bike disc brakes just because they didn’t want to add extra weight to their bike – but they weren’t against the idea of other riders using disc brakes.
Trials for disc brakes were resumed in 2017. Then, on July 1st, 2018, disc brakes were finally approved by the UCI for road racing. This was on the condition that the discs had chamfered, blunted edges to reduce the risk of injury.
Disc Brakes Vs Rim Brakes On Road Bikes
4 Advantages Of Disc Brakes Compared To Rim Brakes
#1. Stopping Power
Disc brakes have greater stopping power than rim brakes.
Not only does this improve stopping distance in an emergency and allow you to brake later when racing, but you also don’t have to apply as much force to the brake levers in order to decelerate the same amount – meaning less tired forearms on big descents.
#2. Braking Control
Disc brakes tend to offer the rider a greater degree of braking precision. Although the high stopping power of disc brakes means it’s easier to lock up the wheels, once you are familiar with them you can easily dish out exactly as much braking as you need without accidentally locking up.
Braking power is applied in a more linear fashion with disc brakes, meaning that as a rider gradually presses on the levers, the brakes are gradually applied more and more.
This is in contrast to rim brakes, whereby the braking is much less consistent. In other words, you might start to pull the levers and nothing changes, then once you reach a certain point the brakes are suddenly powerfully applied.
This linear consistency from disc brakes offers the rider considerably more control.
Disc brakes perform much better than rim brakes in adverse weather conditions. Rim brakes are notoriously rubbish in the rain, whereas road bike disc brakes are considerably less affected.
This is partly because the braking surface of a disc brake is further from the ground, meaning it is less likely to be clogged by debris. Also, holes in the disc mean water and debris can easily pass through.
Additionally, many disc brakes have self-adjusting mechanisms that move the pads closer to the disc as they start to wear down.
One further advantage is that if disc brakes break, the disc can easily be replaced. If the braking surface on a rim brake (i.e. the wheel’s rim) is damaged or worn, the wheel may need to be replaced, which is a much greater cost.
Furthermore, different-sized discs can be custom installed, depending on whether the rider wants to minimize weight by opting for a smaller disc or prefers to maximize braking power and heat dissipation by opting for a disc with a greater diameter.
3 Disadvantages Of disc Brakes Compared To Rim Brakes
Disc brakes have traditionally been heavier than rim brakes, which is a significant disadvantage on racing road bikes where lightness and speed are the top priority.
The reason for the increased weight is that the braking mechanism itself is heavier, and also because the wheels often need to be reinforced in order to withstand the braking force applied around the disc, which adds further weight.
However, technological innovation means that disc brakes nowadays can still be incredibly light. The UCI sets a 6.8 kg weight minimum for bikes in competition, but there are modern disc brake road bikes that are lighter than this. This means the disadvantage of increased weight is not hugely significant nowadays.
Disc brakes are generally considerably more expensive than rim brakes. Furthermore, the frame and wheels must be specifically designed for disc brakes, meaning that you can’t simply just add disc brakes to a bike that was built with rim brakes.
Whilst they don’t offer quite the same stopping power, technological advancements mean that top-end rim brakes are still highly powerful and provide more than enough stopping power for most riders.
#3. Complexity And Repairability
Almost all rim brakes are mechanical, cable-actuated systems, which means they are simple to fix if something in the mechanism goes wrong. This means they’re often easier to adjust and repair whilst out and about.
Furthermore, it is easier to mix and match different types of rim brakes and their components. This is not so straightforward with disc brakes. Their components – particularly on hydraulic disc brakes – are often brand specific.
Mechanical disc brakes offer a little more interchangeability, yet still not to the same extent as rim brakes due to different cable pull ratios and lever types.
Hydraulic disc brakes also have to be bled once a year to keep the fluid fresh, which requires special tools.
Mechanical Vs Hydraulic Road Bike Disc Brakes
Whilst hydraulic disc brakes are the more common type, as road bike disc brakes have increased in popularity cheaper mechanical disc brakes are increasingly available.
Hydraulic disc brakes are more reliable overall than rim brakes and less vulnerable to wear and tear. However, when they do fail, they tend to fail completely and are complex to repair.
On the other hand, cable-actuated mechanical disc brakes are slightly less powerful. This is because the cables have some stretch in them, meaning it is harder to apply the same amount of force. However, they still tend to have more stopping power than rim brakes of a similar standard.
At the professional level, it’s worth considering that hydraulic disc brake cables can be easily routed internally through the frame without the risk of compromising braking power.
This results in better aerodynamics as there aren’t cables poking out around the frame, an advantage that hydraulic disc brakes have over both cable-actuated disc brakes and rim brakes.
So, Should You Be Using Road Bike Disc Brakes?
Put simply: Yes, you should probably be using road bike disc brakes if you can afford them.
Road bike disc brakes provide better braking power, increased safety, and better reliability. Yet, this certainly doesn’t make rim brakes obsolete. Their simplicity, cost, and repairability mean that for many cyclists, they are likely to remain a favorite for years to come.