Head Tube - Castor Angle

Castor Angle

The steering axis angle, also called castor angle, is the angle that the head tube and hence the steering axis makes with the horizontal or vertical, depending on convention. The steering axis is the axis about which the steering mechanism (fork, handlebars, front wheel, etc.) pivots.

• In bicycles, the steering axis angle is called the head angle and is measured clock-wise from the horizontal when viewed from the right side. A 90° head angle would be vertical. For example, Lemond offers:
  • a 2007 Filmore, designed for the track, with a head angle that varies from 72.5° to 74° depending on frame size
  • a 2006 Tete de Course, designed for road racing, with a head angle that varies from 71.25° to 74°, depending on frame size.

• In motorcycles, the steering axis angle is called the rake and is measured counter-clock-wise from the vertical when viewed from the right side. A 0° rake would be vertical. For example, Moto Guzzi offers:
  • a 2007 Breva V 1100 with a rake of 25°30’ (25 degrees and 30 minutes)
  • a 2007 Nevada Classic 750 with a rake of 27.5° (27.5 degrees)