Why do my wheels/bearings rattle

We occasionally get emails from customers asking why their wheels or bearings make a rattling sound. This is an excellent question and nothing to be alarmed about. With a rockered frame one or two of the wheels are generally not touching the ground some of the time. This is in contrast to a flat frame, for which all the wheels are always touching the ground. While skating you will experience vibration that transmits through the frame into the wheels that are floating above the ground. The floating wheels will then vibrate on the axle because of the clearance between the inner bearing race and the axle shaft. That vibration manifests as a noise one hears as “rattle”.

The hole through a typical bearing race is 8.00 mm in diameter. The diameter of the steel axles we ship with most of our frames are 7.85-7.90 mm. This play between the two parts creates the clearance necessary for the axle to easily insert through the bearing. The difference between the size of the axle and the size of the bearing is also what leads to the "rattle." Because our frames are very rigid and resonant the frames tend to amplify the sound a little. Other frames may have axles that are slightly larger in diameter, or have frames that dampen vibration more. Or they simply don’t have the same amount of rocker, or have no rocker at all. Also, the brand/type of bearing used can contribute to the phenomenon depending on the internal clearances of the bearing itself. When all four wheels are flat on the ground the conditions for rattle don’t occur. 

We always recommend checking that your bearings are seated properly and that the anxles are installed correctly. When everything is properly installed there shouldn't be any side to side clearance between the wheel and the frame walls. In other words the frame walls should be clamped to the sides of the bearings.

It’s worth noting that our Ultra Axles have a slightly larger diameter that decreases that clearance with the bearing. This may result in less rattle.