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Road bikes: disc or rim brakes?

For decades conventional road bikes have been equipped with side-pull rim brakes. But as more and more manufacturers are releasing new models with disc brakes, it looks like they might be here to stay.

 

  • What’s the difference between rim and disc brakes?
  • What are their advantages and disadvantages?
  • So which is better?

Comparing rim and disc brakes

It’s hard not to notice disc brakes on a road bike, but outside of their obvious visual difference, there are some differences in operation, ease of maintenance and weight.

Rim brakes

Standard on road bikes for decades, this system is light, easy to adjust and doesn’t require much maintenance. Activation is simple: pull the lever to increase cable tension, so the caliper makes contact between the brake pads and the rim.

Disc brakes

Common on mountain bikes, disc brakes use a metal rotor on the wheel’s hub, and a fixed caliper to compress the rotor.

They function either mechanically or hydraulically. Mechanical disc brakes are similar to rim brakes – you use a lever to increase tension on the cable to compress the pads on the rotor. Hydraulic systems are a little more complicated. Brake fluid housed in the master cylinder in the lever body pushes out into the system via a hydraulic line. By pushing fluid toward the caliper, the pads powerfully compress onto the rotor.

advantages and disadvantages

There are clear advantages and drawbacks to each system.

Advantages of disc brakes
  • Power: disc brakes provide substantially more stopping power than rim brakes.
  • Consistency: they are not adversely affected by wet weather.
  • Modulation: you get an exceptional degree of modulation – precision between lightly feathering the brake and applying peak power – that results in smoother, more controlled braking.
  • Efficiency: discs give you a greater mechanical advantage than rim brakes. Less pulling force is required to apply the brakes.
  • Heat dissipation: during long descents, rim brakes can heat the rim, resulting in fading or loss of braking power – especially with carbon fibre wheels. Disc brakes stay much cooler, and won’t fade.
Disadvantages of disc brakes
  • Maintenance: hydraulic disc systems are particularly complicated. While they are extremely reliable, they will eventually need maintenance, and bleeding the brake line can be a messy and involved job.
  • Weight: because they use additional equipment, both mechanical and hydraulic disc systems come with a weight penalty, and are heavier than rim brakes.
Advantages of rim brakes
  • Weight: usually made of lightweight aluminum, rim brakes are substantially lighter.
  • Maintenance: rim brakes are easy to maintain. Other than brake pad wear and slight adjustments, they are very reliable.
  • Aesthetics: this may be subjective, but many committed roadies appreciate the timeless aesthetic of rim brakes, (as well as riding without socks, using handlebar tape that matches the saddle colour, and so on.)
Disadvantages of rim brakes
  • Power: rim brakes are less powerful than hydraulic or mechanical disc brakes.
  • Consistency: their performance decreases rapidly in wet or muddy conditions. You’ll notice the difference most if you ride with carbon fibre rims.
  • Rim wear: eventually, they wear down, or pit, your wheel rims until the rim or entire wheel need replacing.
  • Modulation: while some rim brakes offer good modulation, they can’t compare to the amount of control offered by disc brakes.

So which is better?

For performance, disc beats rim – no question. If you’re looking for the best overall braking performance on a road bike, a hydraulic disc setup is best by a significant margin.

However, if you’re interested in keeping your bike as light as possible, you might still opt for rim brakes. The newest technologies – rubber compounds, and rim coatings – offer quite sophisticated performance and excellent stopping power without the weight penalty of discs.

Still not sure which to choose? Talk to our bike techs, go for a ride and see what you like. After all, it’s hard to refute rider preference.