Ever wonder if your wheel lock nut is on too tight? Are you afraid you might me damaging your bearings because your wheels are too loose? Take the guess work out of it and get some bearing spacers!
Bearing spacers go between your bearings inside your wheels and act as a brace for your bearings. With bearing spacers in place you can tighten your wheel locking nut tight and still turn your wheels freely. Without a spacer if you tighten your lock nut too far you start to push the center of the bearing into negative space. Because your wheel hub has a lip on the inside, the outer rim of the bearing can't follow the center, and your bearing starts to flex.
Spacers eliminate that negative space and with the pressure of the lock nut, link your bearings together so they turn simultaneously.