One trick that Korey Kier of NW Scoot taught me utilizes the physics of heat and cold to give yourself just a little wiggle room when installing bearings. Put your bearings in the freezer for at least 30 minutes. In the mean time, put your wheels in the hottest water you can find. You may need to boil water, although you don't want to put them in while the water is actually boiling or you might risk melting the urethane. I use the instahot tap on our sink and it works well. After about 10 mintues, I dump the water and add more hot water from the instahot tap.

After 30 minutes of heating and cooling, yank the wheels and the bearings out and quickly assemble them before they return to room temperature. The theory behind this is that the heat expands the wheels just a little bit and the cold contracts the fag bearings just a little bit. It's an immeasureable difference, if any, and I've had mixed results with this technique, but it's worth a shot. I like to combine this technique with grease, but you've got to be fast before the temperature difference neutralizes.

If you still can't coax your bearings into the wheels, you're now going to have to resort to some kind of physical force to complete the task. I've tried using an allthread rod with some washers and nuts from Home Depot to compress the koyo bearings into the wheels, but this, too, gave me mixed results, often breaking the allthread or jamming the bearings in slightly crooked.

When you resort to the hammer, you've got to do it right. First, make sure you're supporting the wheel on a firm, hard, stable, even surface. You can either place the bearing on the surface and hammer the wheel down on to it or you can hammer the bearing into the wheel. Either way, you're going to want to use a heavy rubber mallet and you're going to need something to apply even pressure to all parts of the bearing or wheel, whichever you are striking.

Most often, I'll put the wheel on the bottom and strike the bearing using a socket from my socket wrench set that is approximately the same diameter as the bearing. Place the closed end of the socket against the bearing so that as much metal as possible is in contact with the [scooter bearings], which is designed for vertical (outside to inside) pressure, not lateral (side to side) pressure.

There's got to be a better way to do this, right? After a few frustrating moments, I'm sure you're ready to buy whatever tool is the right tool for the job. Well, it turns out that there is a right tool for this job.