Rim Brakes vs. Disc Brakes: Which is Better?

May 28, 2023

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Photo: Brad Kaminski/Triathlete

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Triathlon is in the midst of a bike revolution. Recommended tire sizes are moving from 25c to 28c, tubeless is the go-to over clincher wheels, and brake styles are moving from rim brakes to disc brakes at a rapid pace. While the new technology available to pros and age groupers alike is exciting, if you aren't a professional triathlete who receives a new bike each season or an age grouper with lots of money to spare, it is easy to get "bike envy" these days.

Disc brakes vs. rim brakes is the jumping off point where many other bike upgrades, like bigger tire sizes, fall into place. But how much does this new brake tech really matter?

For the average athlete, not as much as you’d think.

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Rim brakes are the decades-old way of braking on road and time trial bikes. A rim brake operates with two calipers in the front and rear of the bike. In those calipers sit thick brake pads. When a rider squeezes their brakes, a lever compresses, forcing the brake pads to push against the rim of the wheel, thus slowing the bike via friction.

Rim brakes come in two main types: aluminum and carbon. Aluminum rim brakes are not actually made of the metal, they are instead designed to work best on aluminum wheels. Same goes for carbon rim brake pads; they’re not made of carbon, but are designed to not scratch the carbon on race wheels. Over time, any type of rim brake pad will wear down from frequent use.

The market is trending away from rim brakes for a variety of reasons, but not everyone is sold on making the change just yet.

Professional triathlete Danielle Lewis nabbed a podium spot at 2022 Ironman Arizona on a rim brake bike and has found herself at the front of the pro field many times this past year sans disc brake bike.

"Personally, I don't have an issue with rim brakes," Lewis said. "I’ve raced in rainy and hilly conditions and performed well with the rim brake set up."

Gustav Iden famously won the 2022 Ironman World Championship on a rim brake Giant Trinity bike. He was one of just a handful of male pros who opted to ride with rim brakes in Kona – and clearly, things turned out just fine for him.

Brown wanted to remind athletes that what matters is the rider feeling good about their setup instead of trying to accumulate the latest technology:

"There's not one fastest setup," Brown said. "It wasn't long ago that all bikes were rim brakes, and some of the new [rim brake wheel] setups are still super fast."

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Disc brakes are the bike upgrade most triathletes are lusting after. After being used in the mountain biking world for many years, disc brakes were approved for use in draft-legal and non-drafting triathlon in 2016.

Disc brakes operate via the use of hydraulics. Two small brake pads (much smaller than rim brake pads) sit millimeters apart on the bike frame. A disc on the bike wheel slides in between them. When the brake lever is squeezed, there's an increase in pressure on hydraulic fluid in the brake lines, which then compresses the brake pads, forcing the disc on the wheel to cease rotating, thus stopping the wheel and bike.

"The biggest benefit of disc brakes is you have so much more [on the bike] to play with aerodynamically," Brown said. "You aren't limited by having a vertical [rim] brake track, so you can run a wider tire and get creative with front end and fork setup."

RELATED: Disc Brakes: Do Triathletes Need Them?

If saving a few watts here and there is your goal, it may make sense to splurge on the ultra-accurate disc brake bike models. But keep in mind, the rim brake isn't dead yet. If you have an existing rim brake bike setup you are confident and comfortable riding powerfully during a race, that may outweigh any benefit you would get from changing to a disc brake bike. Like with most things in triathlon: there is the "optimal" way, and then there is the way that suits the individual athlete and their goals. When it comes to brakes, there are "optimal" answers, and then there is the answer that allows you to ride with confidence. Always choose the latter.

RELATED: The Origins, Evolution, and Future of the Tri Bike