Head tube
The head tube is the part of a cycle's tubular frame within which the front fork steerer tube is mounted. 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.
Bearings
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.
- In motorcycles, these bearings are also referred to as headset, or steering head bearings or steering neck bearings. These are usually tapered roller bearings.
Caster angle
- 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’
- *a 2007 Nevada Classic 750 with a rake of 27.5°
Head tube diameters
- Bicycles
| Steerer column nominal OD | Headset standard | Head tube nominal ID |
| 1"/25.4 mm | 1" JIS | 28.8 mm |
| 1"/25.4 mm | 1" ISO | 30.0 mm |
| 1"/25.4 mm | 1" BMX/OPC | 32.5 mm |
| 1"/28.6 mm | 1" standard, threaded and threadless | 33.8 mm |
| 1"/28.6 mm | IS 1" integrated 45×36 | 41.1 mm |
| 1"/28.6 mm | Campagnolo "Hiddenset" 45×45 | 41.9 mm |
| 1"/28.6 mm | Zero Stack/ Internal | 43.9 mm |
| 1"/31.75 mm | 1" standard | 36.8 mm |
| 1.5"/ 38.1 mm | 1.5" standard | 49.6 mm |
- Motorcycles