How to keep cool with road disc brakes

Disc brakes have invaded the road bike market over the past three years. Unlike the high tech mountain bike equivalents, most road bikes are fitted with undersized 140-160 mm rotors and cable operated calipers. Hydraulic systems are now available from both SRAM and Shimano, but they are very expensive and typically fitted on high end models. Moreover, the hydraulic system per se only partially goes to solve the problem of undersized disc rotors and might in fact bring more problems than it solves, when it comes to overheating.

Currently, I run a generic Hayes CX 5 cable operated rear caliper and a semi hydraulic cable operated front (TRP HyRD) which give me the braking force needed to stop a 70 Kg man on a 10 Kg bicycle. In the past, over heating pads and rotors has been an issue when coming down double digit gradients sustained over more than one Km.

I recently fitted a front Shimano 99 Freeza rotor, built with an aluminium core and fins to speed up the cooling. That certainly is a step up in hardware, but ultimately I have learnt that keeping discs cool is not down to hardware, but braking technique.

P1030042

I had to retrain myself to use the brakes in short, sharp squeezes, alternating periods to rest the pad and allow it to cool. Using this simple technique virtually eliminates the problem of overheating and brake fade. This week, I tested the technique coming down San Giacomo di Andrate in the western Alps, which boasts a 2 Km section at 13% with twists and bends and Santa Maria di Scalaro, which has 22 hairpins over 6 Km at 10% average. The latter descend is so technical that it took over 10 minutes to come down alive and at the bottom my hands felt exhausted, but no brake fade! Here’s a map for the Strava crowd, refer to the second climb/descent.

https://www.strava.com/routes/4453961

Here’s three simple  rules to avoid A & E when descending a steep road with disc brakes, or in fact any brake.

  1. Use sharp and short squeezes (1-2 seconds max)
  2. Don’t allow the speed to build over 50-60 Km/h if the road is steep and twisty or you won’t be able to slow enough before the next bend using short squeezes as above.
  3. Listen to your pads, they do sound different as they heat up: they might squeal or hiss, it’s a warning sign, it means your squeezes are too long, keep them shorter.
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4 thoughts on “How to keep cool with road disc brakes

  1. Funnily enough I recall Richard Hallett giving the same advice on technique, following a trip to Shropshire that included the descent off the Long Mynd. In his case the brakes concerned were conventional calipers, and the aim was to avoid blowing the inner tube through overheating.

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  2. In motor racing, it is also generally accepted that short hard brake applications cause less brake overheating. The supposition is that hard braking actually vaporizes and ablates brake pad material, diverting useful amounts of thermal energy away from the rotors and from the pad backing, piston, and brake fluid.

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  3. Having read this post I wonder just how much faith I may have placed on my disc brakes and how close I may have come to failure….. I was recently in French alps and as a 135kg rider getting up to 65/kmh on some very steep sections my Ultegra hyrdo brakes felt strong all the way down, with cheap £9 rotors I might add.

    The biggest descent was this ride: https://www.strava.com/activities/946064283

    Came off it with very sore arms and wrists having been constantly on the brakes. The only thing I noticed was they were making kinda pinging noises as they cooled down at the bottom.

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