Bearings

Each skateboard wheel is mounted on its axle via two bearings. With few exceptions, the bearings are the industrial standard "608" size, with a bore of 8 mm, an outer diameter of 22 mm, and a width of 7 mm. These are usually made of steel, though silicon nitride, a high-tech ceramic, is sometimes used. Many skateboard bearings are graded according to the ABEC scale. The scale starts with ABEC1 as the lowest, 3, 5, 7, 9. It is a common misconception that the higher ABECs are better for skateboarding, as the ABEC rating only measures tolerances, which do not necessarily apply to skateboards.



The ABEC rating does not determine how fast or how durable a bearing used for skateboarding will be. In particular, the ABEC rating says nothing about how well a bearing handles axial (side-to-side) loads, which are severe in most skateboard applications. Many companies do not show the ABEC rating, such as Bones Bearings, which makes bearings specifically for skateboarding, often marketed as "Skate Rated". Each bearing usually contains 7 steel or ceramic ball bearings, although other configurations are used as well.