Head tube
From Wikipedia, the free encyclopedia
The head tube is the part of a cycle's tubular frame within which the front fork steerer tube is mounted.[1] On a motorcycle, the "head tube" is normally called the steering head. On bicycles the manufacturer's brand located on the head tube is known as a head badge.
The head tube holds the bearings which allow the front fork steerer tube to pivot freely.
- In bicycles, these bearings are collectively called the headset. These are usually ball bearings, although some headsets use needle bearings.[2]
- In motorcycles, these bearings are also referred to as headset, or steering head bearings[3] or steering neck bearings.[4] These are usually tapered roller bearings.
Caster angle
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.
- 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. Some examples of caster angles are:[5]
- 72.5° to 74° on the track bicycle 2007 Lemond Filmore, designed for the track (angle varies depending on frame size)
- 71.25° to 74° on the road bicycle 2006 Lemond Tete de Course, designed for road racing (angle varies 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. Some examples of caster angles are:[6]
- 25.5 degrees on the streetfighter 2007 Moto Guzzi Breva V 1100
- 27.5 degrees on the cruiser 2007 Moto Guzzi Nevada Classic 750
