Bikes with disc brakes are slower
Well, this can be TRUE and FALSE.
It is TRUE that disc brake installations add aerodynamic drag, because
- They increased frontal area and airflow disturbance due to the bigger front hub, the disc brake calliper and rotor.
- There are usually more spokes on the wheels, and more spokes = more drag. In disc wheels, a minimum of 24 spokes is required to absorb the forces through the wheel, because the braking torque needs to be transmitted from the hub to the tyre. (Rim brake wheels, on the other hand, can be built with 16 spokes).
But, it is also FALSE because disc brake wheels offer other performance benefits:
- They allow more freedom for wheel design, including wider rim widths which have been shown to improve sailing effect
- A narrower head tube design is possible with a disc brake installation, reducing frontal aera and hence, drag
- You can brake later and carry speed for longer, and you also have more consistent braking performance in all conditions, meaning adverse weather won’t have as much impact on overall speed.