The Next Generation of Rim Brakes Has More Than Meets the Eye

Grippy new rim designs are putting brake pads in the spotlight

Disc brakes are coming (see Cervélo’s P5X and the Diamondback Andean), but rim brakes still dominate the transition area—and engineers are working hard to amp up their stopping power with new textured braking surfaces.

The idea is simple but effective: to create more friction on the braking surface, allowing the brake pad to grab the rim with more bite. Zipp’s new braking surface, for example, uses technology “first developed for application in racing yachts for its high friction and high abrasion resistance in both dry and wet conditions,” says Michael Hall, director of advanced development at Zipp.

Pads must be rejiggered to hold up under the grittier conditions, and a lot of thought has gone into that rim-pad relationship.

“Confidence is king,” says Kevin Nelson, composites engineer at ENVE, a components company that’s now using a harder compound in its pads for textured surfaces than the softer rubber typically used for smooth rims. “We work on our pads for both wet and dry conditions, but a lot of it is about that initial touch and initial power with smooth modulation, regardless of conditions. Having a pad and rim system that provide even modulation means that you get confident in the braking experience, and ultimately you’re staying in your aero position and not even reaching for your brakes.”

With grippier new braking surfaces, it’s vital to ensure that the rough rim isn’t scouring your pads down, so get in the habit of checking your pad’s wear indicator to know when it’s time for a new set. If you’re swapping between alloy and carbon rims, it’s also important to be smart about which type of pad you are running—while it may seem inconsequential, it’s not. Think of it like a point guard wearing a pair of soccer cleats in the NBA finals—they’re shoes, but clearly the wrong tool for the job.

Pads for carbon rims, for instance, are created with compounds capable of managing excessive friction heat (more than 300 degrees F) under high-speed braking load. Alloy rims, which dissipate heat better, utilize pads with rubber blends that are ideal for managing load and wear challenges unique to alloy. “Another issue when using one pad for everything is you can pick up materials like pieces of aluminum on an aluminum rim that can bed into a brake pad and cause issues,” Nelson says. Not to mention, using pads meant for textured surfaces on smooth rims can void the warranty.