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Aerodynamics of Disc Brakes

Since the introduction of disc braking on road and time-trial/triathlon bikes, a debate has existed as to the benefits from enhanced braking performance versus the suggested aerodynamic penalty of a disc brake setup.  Prior testing of our first generation of disc brake wheels has shown that by optimising the tyre/rim interface, taking advantage of no longer needing a brake track at the rim, we can reduce any aerodynamic penalty from the brake rotor.  With the most common rotor size of 160mm, the aerodynamic penalty was less than 1W, whilst using a smaller 140mm rotor would reduce the penalty to only 0.3W.  Removing the rotor altogether (not recommended for ride use!), the disc brake wheelset was 0.6W faster than its rim brake equivalent.

Full details of the initial testing can be found here:

With the introduction of our #thinkwider rim profiles on the Strade and Ronde wheelsets, we have moved beyond the direct comparisons as these wheelsets are now optimised around a 28mm tyre.  As a result, we can no longer compare like-for-like with the rim brake line-up in a fair test.

However, as disc brakes have become more prevalent, there are an increasing number of rotor designs available to riders.  We therefore wanted to test (and quantify) the difference in aerodynamic performance between these designs.

Test 1: January 2019

WheelBrake rotorAerodynamic drag delta at 30mph
Passista DiscSRAM Centerline 2-piece (160mm)
Passista DiscCampagnolo AFS (160mm)+ 0.3W
Passista DiscShimano Dura Ace + 0.3W


  • All test runs conducted using the same Passista Disc (56mm) front wheel, fitted with a Schwalbe Pro One 23mm tyre

Test 2: November 2020

WheelBrake rotorAerodynamic drag delta at 30mph
Ronde             Shimano XTR RT-MT900 (160mm) 
RondeSRAM Centerline 2-piece (160mm)+ 0.6W
RondeShimano Dura Ace Ice Tech (160mm) + 1.1W


  • All test runs conducted using the same Ronde (35.6mm) front wheel, fitted with a Continental GP5000TL 28mm tyre


Based on this testing, it is clear that there is a material (and measurable) difference in aerodynamics between brake rotor designs.   

It is also noteworthy that the difference between the SRAM Centerline rotor and Shimano Dura Ace rotor has grown from 0.3W in the January 2019 test to November 2020 test.  Whilst it is possible some of this can be attributed to margin of error in the wind tunnel, the difference is still sufficiently consistent to suggest other factors at play.  The most significant influence is likely to be the difference in hub design  between the first generation Passista Disc and the current generation Ronde.