When the brakes are applied, the kinetic energy of bike and rider is rapidly converted into heat through friction between the brake pad and braking surface. On a carbon brake surface, this heat can cause issues in one of two ways:
As a result, when looking at the rim design, we wanted to ensure we had the most heat-resistant options available. To do this, Parcours wheels use an industry-leading high TG resin. The brake track itself also uses a basalt coating, which is an excellent thermal insulator.
Furthermore, for our current generation of rim brake wheels, we have introduced a textured brake track surface that now increases the grip between pad and rim. We use the same brake track resin which has been laser etched to provide the textured surface. Our ride testing has shown that this materially improves braking performance, in particular in wet riding conditions.
To put the braking performance to the test, we put our rims through a repeated braking cycle, using a thermal probe to monitor the rim temperature.
As with our aero testing, to keep things transparent, here is the test protocol:
Below is a chart showing a snapshot of the results:
At no point does the rim temperature rise above 130°C, which keeps it well below the all-important TG of the carbon fibre resin (300°C). It is also well below the TG of a standard butyl inner tube. Note that latex inner tubes have a TG more towards 120°C, so worth bearing in mind if you’re planning on riding them when you’re expecting prolonged periods of braking.
As with our aero testing, it’s important to take into account real-world riding conditions. Parcours wheels have been tested across all terrain, ranging from short, sharp Lake District downhills in the rain too long, sweeping Alpine descents in summer heat. Each time they performed admirably, with no unpleasant surprises or issues.
So what does all the testing tell us, particularly about braking on Parcours wheels? Ultimately, our goal is to keep the rim temperature down, meaning we steer well clear of the critical glass transition temperature. To do this, you can employ a number of techniques: