Bearing Spacers

[FastAirInMyHair]

I've been looking for a thread about bearing spacers here for some time, and cannot find one.
I do not use bearing spacers and i dont understand why you would ever have to. Don't the wheels space them apart anyways?

[SteveC]

Yes but they only space the outer half the bearing.
which means that during cornering only one bearing is taking all the side loads. An accurate spacer distributes that pressure to both bearings.

[Wells]

Using [precision, steel] bearing spacers keeps everything straighter, more precise, and truer; and allows you to crank down the axle nuts without putting a huge side-load on the inner race of the bearing. The effect is significantly more dramatic on a wheel with a precision core as opposed to a spitfire or mini-logo.

Also, if you're properly spaced and tightened, your wheels will slide more smoothly and silently.

[hexagon5un]

What they said...

When you tighten the nut, it puts pressure on the inner bearing race, but the wheel cores only contact the outer rims of the bearings.

So when you squeeze the bearings together without spacers, the force goes from the inner race, through the balls to the outer race, across the wheel core, and back down through the other bearing. You're putting an unnecessary shear force on the bearings which stresses them. The balls are getting squeezed in addition to squashed. Nobody wants their balls squeezed.

Put spacers in and they bear the load straight across. Inner race to spacer to inner race and you're done -- the balls don't have to suffer the stress of tightening the wheel nuts. With no extra pinch on the bearings, the balls rotate more freely, and should wear less in the long run.

As a bonus, you can really crank them down tight, eliminating a lot of slop in the system so your wheels corner/slide better without chatter.

[Mile_High_Mark]

And steel spacers don't "compress," so you don't have to worry about them "shortening" over time.