Rim brakes or disc brakes? Choosing which kind of brake to use for your ride has become a recurring debate, as more bike brands begin releasing and promoting disc brake-compatible frames. But is it time to move on to disc brakes, or is there space still for rim brakes in triathlon?
Disc brake calipers apply braking force to rotors mounted on the wheel hubs, while rim brake calipers apply that braking force directly onto the brake track on the rims of the wheel. As a result, disc brake and rim brake systems are not compatible with each other, and you can’t convert a rim brake-compatible bike frame to use disc brakes.
The bike industry seems to be pushing disc brakes more and more, with all World Tour cycling teams using disc brake systems now. However, the muddy 2021 Paris-Roubaix race has seen a debate on whether or not rim brakes would have served cyclists better with slower wheel changes and certain types of disc brake pads not working in the conditions.
Weight and Aerodynamics
Rim brakes are lighter than disc brakes. If you include all the parts that come with a disc brake set such as the rotors, calipers, and other components, it will add an additional hundred grams to your bike.
However, with the developments in disc brake design and new integrated calipers in the bike frames, disc brakes are becoming more aerodynamic than earlier iterations with wind tunnel tests showing that they might even perform better than rim brakes in some conditions.
This is the area where disc brakes perform better than rim brakes. Disc brakes can hold up better in any kind of weather condition partly because the discs are farther from the moisture and mud coming from the wheels. Especially in wet conditions, rims are more slippery which make rim brakes less effective.
Because of the larger surface area granted by the rotors, disc brakes can produce more friction (=braking power), so you can brake later and take more speed going into dead turns, for instance.
Hydraulic disc brakes (with fluid-filled brake lines like the ones motorcycles use) have even better stopping power, needing less effort from your hands than mechanical disc brakes which rely on cables to press the brake pads to the braking surface.
Rim brakes are simpler and cheaper to install than disc brakes, and are usually designed with lots of clearance to make sure the calipers and wheels fit properly and don’t scrape against each other when freewheeling.
Disc brakes need a bit more specialised skill to install and maintain, especially the hydraulic disc brake systems. While it’s true that hydraulic disc brakes save you maintenance time because they are self-calibrating as the brake pads thin out, you’ll still have to check the pads regularly. The hydraulic lines will also need to be bled regularly to ensure no air bubbles are in the system so they can work properly.
However, rim brakes cause more wear and tear on wheel rims, meaning the whole wheel will need to be replaced instead of just the brake pads. Even though both rim brakes and disc brakes heat up with prolonged braking, this is less of a problem with disc brakes (which is why they’re the preferred brake of downhill mountain bikers). Excessive heat in the rims may cause damage to tubes, tires, and the rims themselves.
The advantage of rim brakes in this regard is that rim brakes are easier on the fork legs than their counterparts. Because rim brakes are stationed high on the fork near the stem, there is less force being put on the fork legs. And because the brakes are placed near the rim, there is less strain on the spokes, ensuring that your wheels last longer (except if you wreck the braking surface).
Rim brakes are generally cheaper than disc brakes, partly because they are simpler and consist of fewer parts. You don’t need rotors in rim brakes because the rim acts as the rotor. Disc brake parts are generally more expensive, especially the rotors, calipers and brake pads.
(Bike frames compatible with disc brakes tend to be on the pricier side as well. Because braking force is applied on the non-drivetrain side of the bike frame, the frame has to be built with stiffer material.)
Disc brake parts are also harder to find than rim brake parts. This is especially true when you live in or are traveling in remote countries that don’t carry disc brake parts, requiring you to ship them in at a higher cost.
Are you someone who prefers to be on the bleeding edge of technology, with the resources to sink money into a brake system even the pros use? Or are you more comfortable knowing you can readily repair and maintain your bike brakes yourself and spend less upfront?
In the end, the decision is up to you, what your needs are, and what fits your budget.