If you skate quads or inlines or a skateboard, you will eventually have questions about mini (micro) bearings specifically 688 bearings. What do they do? Where do they go? Which ones should I get? I'm going to cover all of your questions here.
The Basics
As we are talking bearings for skating, this blog post will only be covering ball bearings. Bearings provide the rotational requirement that your wheels need to move. They allow your wheels to spin. They are a pretty simple machine and only have a few components. An inner race, which connects the bearing to the axle, an outer race, which connects the bearing to the wheel, the actual ball bearings, which provide the spin, and the cage that keeps the ball bearings where they’re supposed to be. Optional on these bearings are shields, which protect these components from outside contamination.
Bont 688 Mini Micro Bearing
Bont 688 Mini Micro BearingBearing sizes
Skate bearings can generally be divided into two groups: Standard and Micro (Mini). Standard bearings will be either designated 608 or 627. 608 bearings have an 8mm inside diameter, a 22mm outside diameter, and they are 7mm in width. They are by far the most popular size and are used in quad skate wheels, inline wheels, and skateboards as pretty much everything has 8mm axles. 627 bearings are identical to 608 with the exception of a 7mm inside diameter.
READ MORE: The Truth About Skate bearings by Alexander Bont. Find out about how Bont tests bearings, which bearing oil is best, how can you tell if a bearing is good or not and many other 608 bearing questions.
Why are there so many bearing sizes?
An axle is the part of the roller skate that the wheels slide onto. Axles come in two thicknesses which are 7mm and 8mm. 7mm axles are lighter but they need to be made of more expensive materials to make sure they are strong enough so 8mm has become more of a standard size for today's roller skates.