The head tube is where the fork of a motorcycle or bicycle is attached to the frame, and it houses bearings for steering. It can be made of various materials, and the angle affects fork rake and steering. Headsets include bearing cups, bearings, and races.
A head tube is a part of the frame of a motorcycle or bicycle. It is the place where the fork of the motorcycle or bicycle is attached to the frame, and the steerer tube usually houses bearings that allow the steerer tube of the fork to move freely. The head tube is also often where the head badge, a decoration to identify the manufacturer, is attached, although this is more common on bicycles than motorcycles. The tube is welded or secured to the rest of the frame at the junction of the top tube and down tube. Frame materials vary depending on the type of bike the tube is a part of.
Motorcycle frames are often made of steel for strength, so a motorcycle’s head tube is often made of steel. Bicycle frames, on the other hand, can be made from a variety of materials for strength and weight savings. Steel is commonly used, as is aluminum, chromol – steel alloyed with chromium and molybdenum – titanium, scandium and carbon fiber. If the head tube is made of carbon fiber, an aluminum or steel insert is often inserted into the tube for added strength and durability. Regardless of the material used to make the steerer tube, bearings must be inserted into the tube in order for the fork to move freely from side to side, making steering possible.
The angle at which the head tube is welded or otherwise attached to the frame dictates fork rake, or the angle at which the fork protrudes from the frame. Rake will affect the steering and shock absorption of the fork, and if the rake is too harsh or too loose, the fork can put excessive stress on the joint between the steerer tube and the other tubes on the bike, which will cause cracking, flexing or loss of control of the vehicle. Most frames are carefully designed with fork rake in mind; Chopper bikes will very often have a long rake for style and visual appeal, while a sport racing bike will have a very tight rake for quick steering.
The bearings inserted into the tube are part of a unit called a headset. On bicycles, headsets include bearing cups that are pressed into the tube, the bearings themselves, and bearing races that press on the bearings when the unit is tightened. The earpiece may be an external unit that protrudes from each end of the head tube, or it may be an internal unit that presses completely or nearly completely into the head tube.
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