Technologies
Wheels and tires. There are two general categories of tires on which stand-up scooters travel—hard tires and air tires. Hard tires are generally six inches in diameter and constructed of a hard-plastic insert surrounded by a solid rubber tire. Air tires are most often 10 inches in diameter. They are constructed of a steel or aluminum split rim, an inner tube and rubber tire. Other, less common wheel and tire types include 8 inch and 13 inch air tires.
Transmissions. The most simplistic drive mechanism of stand-up scooters is the "spindle" drive. This drive mechanism puts an extension of the engine's output shaft, the spindle, in direct contact with the rear tire of the scooter. In order to function correctly, the tire must have a clean, dry surface which the spindle will be able to effectively interact with. Scooters with this type of direct transmission can be pull started with the rear wheel off of the ground or "bump" started by forcefully pushing the scooter with the rear tire in contact with the ground.
Simple chain reduction drives are also used to transfer energy to the rear wheel from the engine. These generally incorporate a type of centrifugal clutch to allow the engine to idle independently.
Belt reduction drives use the combination of wide flat "cog" belts and pulleys to transfer power to the rear wheel. Like chain drives, belt drives include a centrifugal clutch. Belt drives are more susceptible to breakage in off-road conditions.
Suspension. The suspension systems of stand-up scooters range from simplistic spring based fork systems to the complicated, dampened cam-link and C.I.D.L.I suspension mechanisms.
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