When a skateboard is set into motion, bearings reduce the friction between the axle and the wheel to keep it in motion. A good set of bearings is essential to any skateboard build.What Do Skateboard Bearings Do?
Bearings are an essential part of skateboard wheels. A bearing sits at the middle of each wheel and consists of inner or outer rings with metal or ceramic balls between them. These balls can roll between the bearings, reducing friction between the skateboard wheel and the axle. This means that the wheel can spin freely for longer, allowing higher top speeds and reducing the amount of muscle power needed to move the skateboard along.Skateboard Bearing Materials
Skateboard bearings are almost always made from either steel or ceramic. Steel bearings are the more common option and are typically cheaper, although many skateboard manufacturers also make extremely high-grade steel bearings. Ceramic bearings produce less friction than steel as they are smoother and less affected by heat, allowing for higher speeds, and their greater hardness also makes them more durable. That increased hardness has a downside, though. Ceramic bearings are more likely to be damaged by heavy impacts.Skateboard Bearing Sizes
Skateboard bearings come in different sizes. However, one size predominates, and is used in most skateboard wheels. This is the 608 standardized bearing, which has an outer diameter of 22 millimetres, an inner diameter of 8 millimetres and a 7 millimetre width. These bearings and wheels will fit onto the standard 8 millimetre axles found on most boards. However, some skateboarders and skateboard manufacturers prefer to use a 10 millimetre axle. This naturally requires a larger bearing, and so several manufacturers build specialised bearings to fit the larger axle.Skateboard Bearing Ratings
The material that skateboard bearings are made from is not the only indicator of how they will perform. ABEC skateboard bearings are rated by their ABEC number. The ABEC number is a reflection of how precisely the bearings are manufactured: the higher the ABEC number, the tighter the manufacturing tolerances, resulting in a bearing that is more precise and more efficient. ABEC 1 bearings are manufactured to the least accurate standards but will typically be the cheapest, while ABEC 9 bearings are built to extremely tight tolerances. However, the ABEC rating is not a direct measure of how fast the bearing will be, and many skateboard equipment manufacturers prefer to use their own scales of bearing speed and efficiency.