Skateboard wheels are attached as a pair at the bottom of a skateboard, held and mounted in place by specialized axles known as trucks. They are normally made from polyurethane, a very hard type of rubber, and range in size between 48 to 100 millimeters. Besides size, skateboard wheels also differ in hardness, as measured by a durometer A scale. The softest ones are at about 75a, while the hardest skateboard wheels are at 99a. Some are also labeled to have ratings of 101a and above but this is inappropriate since the durometer A scale only runs up to 100. For skateboard wheels harder than the hardest skateboard wheels for the A scale, B or D scales are normally used for better accuracy and wider range of hardness.
Kinds of skateboard wheels
Street: Street skateboard wheels measure between 48 to 55 millimeters and are considered to be the smallest in the bunch. They are relatively hard, preventing them from slowing down and absorbing energy but useful for skating tricks like ollies and flips.
Vert: Vert skateboard wheels are specialized for vert skating, which includes landing and jumping on ramps. Sized at 55 to 65 millimeters, they are considered to be one of the hardest skateboard wheels primarily because of their exclusive use on ramps.
Slalom: Slalom skateboard wheels are bigger than vert wheels at 60 to 75 millimeters, with their size allowing them to sustain maximum speeds for a longer period of time. However, they are softer to provide better grips on turns, very important in slalom racing.
Longboard: Longboard skateboard wheels are made for transport and cruising, catering to the primary function of longboards. With sizes ranging from 65 to 100 millimeters, they provide stable and comfortable rides. They normally come with hard plastic cores since using solid polyurethane ones would make them too heavy and too thick.
A quick tip
The softest wheels are ideal for children and beginners. As you go up a skill level, the harder your wheels become.