On the road
Full carbon rims are worlds apart from the aluminum rims you’ve likely spent years riding on, especially when it comes to braking. They’re light, vocal, slippery in the wind, and definitively communicate that you’re applying the brakes.

Carbon wheels sing to you on the road. Maybe I was hallucinating after my first grueling TT on the 69ers, but I swear, they were calling out a low guttural “cahhhrrrrbbuhn” with each pedal stroke. And over the road’s endless ripples and undulations, every little blip adds a percussive note. The subtle chatters and clicks are a symphony, if you’re willing to use a liberal interpretation of that word. After getting accustomed to the unique sounds of the 69er, I’ve grown very fond of the way that that pitch increases with speed, and pulses with each surge of the pedal.

What really takes getting used to are the differences in braking between carbon and aluminum. I can tell you this straight-out – do not just throw a set of any carbon wheels onto your bike, quickly install a set of carbon pads and then head out to a time trial with a technical descent. It takes road time with carbon wheels to dial-in your braking technique.

While aluminum absorbs and dissipates heat very well, carbon does a poor job of absorbing any heat at all. In braking, friction generates heat. And without an aluminum rim surface to absorb some of that heat, brake pads on carbon rims get very hot. Standard brake pads will actually melt from excessive heat build up. Carbon specific pads are the only smart way to go. They withstand heat much better, ensuring speed modulation across a much wider range of temperatures.

Three different pads were compared during the 69er test rides: Zipp Carbon pads by Kool Stop, SwissStop Yellow King pads, and Shimano R55C carbon pads. To rank them, each cartridge pad set was dialed in with the same 1mm toe-in. Zipp recommends their carbon pad for the 69er, and these did work very well.

The Zipp pads exhibited great modulation in typical road conditions. They grab very well in dry and better than a standard pad on an aluminum rim when wet. The only conditions that left me wanting better modulation was on steep sustained descents, which we have lots of here in Santa Cruz; the Zipp pads would seem heat up and start to fade, requiring more brake lever and then revealing a tendency to grab.

The Shimano pads worked reasonably well when cool, but felt binary (off/on) when grabbed a third or forth time – they’d slip with little or no modulation, then fully engage and clamp the rim. This made for unpredictable white knuckled descents.

My favorite pad of the bunch were the SwissStop Yellow pads. These had the same excellent dry modulation as the Zipps, the same wet control, but slightly better resistance to heat build-up on steady descents, with less grabbing.

If you don’t find yourself descending much, the Zipp pads are a great choice, if your rides include steady steeps, I’d recommend the SwissStops. Overall, braking on steep, sustained descents was never up to par to the modulation you’ll find descending with an aluminum rim. Heat build-up on the pads, plain and simple, will diminish braking performance.

But this really points to how you’re likely to ride any set of carbon wheels. I perceive the carbon wheel primarily as a race dedicated product, with the occasional sporty training ride thrown in for fun. And in most race scenarios, you aren’t on the brakes. And if you are on the brakes, you’re off them right away. The only exception I could see would be a mountain stage, or steep road race. In the latter situation, I’d choose to ride an aluminum rim.

Regarding braking performance and maintenance, Zipp recommends keeping the brake track clean with a scotch bright pad and acetone, but be careful; if you get sloppy with the acetone, it will dissolve the decal glue. They also caution against using 3M Fast Tack, warning that it can damage the wheel when removing a tire.

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