Head tube

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A bicycle head tube with a partially installed bicycle headset, the locknut has yet to be fitted onto the fork steer tube.

In vehicle frames, most commonly of a bicycle or motorcycle,[1] the head tube is the outer tube within which the steer tube pivots.

Bearings[edit | edit source]

The head tube holds the bearings which allow the front fork steer tube to pivot freely.

Motorcycles[edit | edit source]

In motorcycles, these bearings are also referred to as headset, or steering head bearings[2] or steering neck bearings.[3] These are usually tapered roller bearings.

Angle[edit | edit source]

The steering axis angle, also called caster 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.

Motorcycles[edit | edit source]

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[4] 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)

Sizes[edit | edit source]

Traditional motorcycle head tubes and headsets are sized for a one inch (25.4 mm) diameter fork steering tubes.

References[edit | edit source]

  1. Chopper kit installation Guide. Retrieved on 2007-04-11.
  2. Motorcycle Cruiser How to Service Motorcycle Steering-Head Bearings. Retrieved on 2007-04-11.
  3. Motorcycle Maintenance. Retrieved on 2007-04-11.
  4. Moto Guzzi USA (2006). Retrieved on 2006-12-11.

See also[edit | edit source]