Longboard Lesson - Wheel Hubs, Bearings & Bearing Spacers
The relationship between wheel hubs, bearings, and bearing spacers have been a subject with much confusion. Last year I did an article on bearing spacers, but didn’t go into the sizing, so I am hoping to shed some light with the following photos and descriptions.
Bearing Spacers are designed to match the distance of space between the 2 bearings when installed inside of wheels. When the wheels are installed, and the axle nut is snug, then your bearings will be properly spaced, thus providing optimal speed and longer lasting bearings.
Bearing spacers come in 4 different sizes. From left to right, they are 8mm x 8mm, 8mm x 10mm, 10mm x 8mm, and 10mm x 10mm. I know, this is very confusing, but all you need to know is that the first number relates to the axle diameter on the trucks and the second number relates to the spacing used inside of the wheel hub. Most of the time you will use the 8mm x 10mm bearing spacers.
Let’s start by looking at the first number, the one that relates to the axle diameter. There are two axle diameters, 8mm [shown below] and 10mm [shown above]. 8mm axles are by far the most common size, and 10mm axles are typically used for racing boards only. At this time, The Longboard Store only offers 10mm axles on the Bear Trucks.
The second number on that bearing spacer relates to the spacing used in the wheel hub. See the center of the wheel above? A bearing is pushed into that hub from both sides until they touch that that tab in the very center, creating a space between both bearings. So the wheel assembly will perform correctly and last longer, we like to fill that space with a metal spacer that won’t be squished when the wheel assembly is tightened. So, that space will be either 8mm wide or 10mm wide, the second number on the bearing spacer. The most common wheel hub spacing will be 10m.
The bearing on the left shows a smaller inside diameter of 8mm, which would be used on 8mm axle trucks. The right bearing has a larger inside diameter of 10mm, and is used on 10mm axle trucks. Again, an 8mm bearing and truck is by far the most common.