How do I fix a center wheel rub?

The Endless 90 frame can have very close clearances to brand new 110 mm wheels in the center position when used in the triskate setup. However, there are occasions where lesser quality parts can create a slight interference or rub between the wheel and the side wall of the frame. Bearings, spacers, and wheels (urethane and core) all have tolerances. Sometimes tolerances can stack up such that the wheel is not centered in the frame, or the frame walls are pulled towards the wheels when the axles are torqued. For the design clearance to be maintained the wheel must be properly centered in the frame. Consider the following issues:

Inexpensive wheels may not have the urethane poured symmetrically on the core, or the core itself may not allow bearings to seat uniformly on both sides. This causes the wheel to be offset to one side of the frame.
Bearings are not firmly seated in each side of the wheel core. This causes the the wheel to be offset to one side of the frame.
The bearing spacers are too short. When all the axles are torqued the frame walls will flex inward more than they should as the bearings are compressed against the bearing spacers. This causes the frame channel width to be reduced slightly.
Wheels with full radius profiles may not have sufficient clearance due to the round profile.
Wheels with widths greather than 24.0 mm may be too wide.
Powerslide Spinner wheels are known to have issues and are not recommended.

Actions you can take to remedy these situations:

Use high quality wheels like Undercover, Rollerblade Hydrogen, MPC, or Junk. Elliptical / bullet profile will work best.
Try reseating the bearings in your wheels by firmly pressing the flat side of the wheel against a hard flat surface. A skate tool can also be used.
If the wheel is offset towards one wall of the frame then try flipping the wheel 180 degrees to balance out the tolerance stack-up.
Try swapping another wheel into the center position. It may be more centered.
Use different bearing spacers. We prefer the flying saucer types with a center flange as opposed to the straight cylindrical types. A fraction of a mm in length may make all the difference you need.