Shimming Skate Axles to 8mm

When a skate wheel has been properly installed, the axle nut is fully tightend to proper torque and a very slight amount of play is felt in the wheel. This play will be play within the bearing itself rather than over the axle. Free spin may not be great, but free spin is not a valid test of proper installation of a skate wheel.

It is so important that bearings be mounted on the axle well. The hanger face should be machined perpendicular to the axle (a counterbore w/ pilot removed works well, MSC #08790644).

Skateboard axles are undersized 5/16" shafts and are on average 0.004" (dia.) less than what the 608 bearing's 8mm bore requires. The axle diameter should be shimmed up to 8mm (.3149")(usually, .0010-.0020" stainless steel shim stock cut to .951" long x.977" wide works well). Curling the shim over the back side of some sissors makes it easier to get the bearing over while holding the shim on the axle.
If the axle has been properly shimmed, the bearings properly spaced, and the hanger properly faced, the axle nut can be tighted to proper torque without harming performance.

In this configuation, the axle is actually supported by the inner races of the bearings and the spacers making the trucks stronger and stiffer.