Handlebars usually refer to the steering mechanism for bicycles and motorcycles; the equivalent of a steering wheel, though used in conjunction with the rider's balance or centre of gravity to steer. There three most common types of bicycle handlebar are

• drop handlebars, as used on road, track and cyclocross bicycles.
• flat or upright handlebars, as used on mountain, utility bicycles and hybrid bicycles. This type of handlebar frequently has bar ends added.
• cruiser handlebars, as used on cruiser bicycles. These tend to be long so that the rider can sit upright.

Additional types include:

• triathlon bars, or aero bars
• bullhorn handlebars, used with dedicated triathlon bars
• moustache handlebars

Handlebar design is a trade-off between several desirable qualities:

• Enabling the rider to assume an aerodynamic position.
• Enabling the rider to change body positions during long rides, preventing fatigue.
• Providing necessary leverage to steer the bicycle.

  Extreme care is needed when choosing a handlebar to match a stem, or vice-versa, as standards are a mess. The ISO standard for the clamping area of a handlebar is 25.4 mm (1"), which is used on the majority of mountain bikes and many Japanese-made road handlebars. However, the Italian unofficial standard is 26.0 mm, which is the most common clamp size for road bars. There are also intermediate sizes such as 25.8 mm to try and achieve compatibility with either an ISO or Italian stem, and the old Cinelli-specific size of 26.4 mm. In practice, many modern stems with removable faceplates are quite accommodating of slight differences in handlebar clamp size, but the older type of stem with a single pinch bolt must be accurately matched. In the days of quill stems, a road stem was clearly identifiable from its "7" shape, but nowadays it can be hard to tell the difference between a "road" (26.0 mm) and "MTB" (25.4 mm) stem. Manufacturers frequently omit the clamp size from advertising or packaging.

  A new emerging standard is an oversize 31.8 mm (1.25") clamp for both MTB and road bars. This is rapidly taking over from the previous mix of sizes, although other accessories such as computers and brake levers also need to be designed with the thicker bars in mind. Shims are available to fit a 31.8mm stem to either a 25.4mm or 26.0mm bar, so it is likely that most new stems will be made oversize-only.

  A handlebar moustache is a man's upper-lip facial hair grown long and waxed, with the overall shape of a bicycle's handlebar.

  Bicycle parts

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