The tires on an all-terrain vehicle (ATV) typically require inner-tubes (tubes) to provide the soft floatation type of traction common with an ATV tire. There are subtle differences in ATV tubes that require a precise match when purchasing a replacement tube for any tire. One of the most notable differences in ATV tubes comes in the size of the tube. Different size tires require different size tubes in order to make a matching tire and tube set. Other differences are found in the type of valve stem that is used with the particular ATV tubes. Using the wrong tube in a tire can void a tire's warranty, in most cases.
The front tires on most ATVs are both narrower and smaller in diameter than the rear tires on the same machine. This is true even in 4x4 type ATVs, leading to the requirement for different sized ATV tubes when changing tires. The extremely low air pressures used in ATV tires require an inner-tube to keep the tire pushed outward against the wheel. If not for the inner-tube, the tire would simply peel away from the wheel when a rock or strange angle is encountered. This is also the reason behind another difference in ATV tubes: the valve stem.
There are three types of valve stems used on ATV tubes: straight rubber pull through, straight metal bolt-in and 90-degree metal bolt-in styles. Each of these is used for a specific purpose and use, and using the wrong valve stem can result in a flat tire. For the most part, all ATVs are equipped with a straight, pull-through type of rubber valve stem in a stock equipment tire application. The rubber valve stem provides adequate performance the typical ATV rider. For tires used in performance or extreme duty applications, a steel, bolt-in valve stem is typically called for.
The steel, bolt-in valve stem locks the tube to the wheel. This is important when the power of the motor drives the wheel to spin inside of the tire, a common occurrence in racing or extremely low air pressure applications. This could cut a rubber valve stem, resulting in a flat tire. The short and straight valve stem protects the stem from being damaged in wheel-to-wheel contact when racing. The steel stem also resists air loss resulting from the same type of contact. A 90-degree steel stem is typically used on the inside of a wheel for the utmost in protection while providing air access to the ATV tubes.