In the middle of every skate wheel, a cutout groove exists to house and shield two sets of ball bearings. These bearings work to eliminate friction between the metal inside of the each wheel and the metal axle it spins around. Because the axle is fixed, the bearings are necessary to let the wheels spin without grinding up the metal. A bolt runs through the center of one bearing, through the center of the wheel, and then again through another bearing, linking up the three pieces of the rotating mechanism and giving you the movement you need to skate.
Bearings are circular in shape with flat sides. Each one houses seven or eight lubricated balls (ceramic bearings have nine), which are designed to disperse the weight of a load and ease tension between the wheels and the axle. These balls are typically made of steel for durability and economical purposes. For most skateboarders, steel bearings will work fine.
Unfortunately, the energy caused by heavy friction between the axle and the wheels can heat up the metal, causing it to expand and render the bearings ineffective. Be careful to keep your bearings clean, lubricated and dry, and they’ll work better and last much longer.
Skate companies recognized a need for bearings that were less affected by heat energy and began offering ceramic bearings for more discerning riders. Ceramic bearings, made from a compound called silicon nitride, are smoother and harder than their steel counterparts. This means much less friction to begin with (these bearings have little need for lubricant); however, should friction occur, the ceramic material doesn’t expand, so there is no effect on the skateboard’s performance.
As usual, higher performance comes at a higher price; but many skaters will tell you that ceramic bearings are well worth the premium.
The most common bearing size is the “608.” Characterized by an 8mm core, a 22mm outer diameter and a 7mm width, these bearings are the industry standard and match up with nearly every skate wheel out there.
NON-STANDARD Of course, there are exceptions to every rule. Rarely, you’ll come across a wheel that is designed for use with a non-standard bearing. This is not common, but it’s something to keep in mind.
There are also mini-bearings that can be used with the standard 608 bearing hub, but they require a sleeve to make them compatible.
The Annular Bearing Engineering Committee (ABEC), a division of the American Bearing Manufacturers Association, developed a rating system to measure the amount of tolerance – or variation from an exact measurement – in precision bearings, a system that became a standard in the bearing industry. ABEC ratings run from 1 to 9 (odd numbers only), with higher numbers meaning more precise tolerances. Typically, the higher numbers also equate to higher prices.
While the ABEC ratings are certainly relevant in some cases, they were designed to evaluate bearings for use in machinery, not skateboard wheels. Unfortunately, the result is that the tolerances measured do not factor in certain forces exclusive to skateboarding. Therefore, while many skate bearing manufacturers will still provide the ABEC ratings for their products, riders should know that they are not end-all.