page_title: Inline skates
section_title: Bearings
hierarchical_section_title: Inline skates / Parts / Bearings
caption_attribution_description: Axles, bearings and spacers of an inline skate.
context_page_description: Inline skates are a type of roller skate used for inline skating. Unlike quad skates, which have two front and two rear wheels, inline skates typically have two to five wheels arranged in a single line. Some, especially those for recreation, have a rubber "stop" or "brake" block attached to the rear of one or occasionally both of the skates so that the skater can slow down or stop by leaning back on the foot with the brake skate.
  The modern style of inline skates was developed as a substitute for ice skates, for use by a Russian athlete training on solid ground for Olympic long track speed skating events. Life magazine published a photo of American skater Eric Heiden, training for the 1980 Olympics, using such skates on a Wisconsin road.
  During the late 1980s and early 1990s, Rollerblade, Inc., a company founded by Scott and Brennan Olson in Minneapolis, Minnesota, widely promoted inline skating through the registered trademark Rollerblade.
context_section_description: Ball bearings allow the wheels to rotate freely and smoothly. Bearings are usually rated on the ABEC scale, a measure of the manufactured precision tolerance, ranging from 1 (worst) to 9 (best) in odd numbers. The ABEC standards were originally intended for high-speed machinery, not skating applications, and do not account for the quality of steel used, which is very important for how long bearings last. While higher rated bearings are generally better in overall quality, whether they automatically translate to more speed is questionable. Since at least 2007, Rollerblade brand amongst others have begun using their own rating system.  For instance, Rollerblade brand is currently using a SG1 to SG9 rating system, whereas TwinCam brand is using its own "ILQ" (InLine Qualified) rating system and Bones brand is using its own "Skate Rated" rating system.
  A mistake that is often made in purchasing bearings is that spending more translates to more speed.  Generally, clean inline skate bearings contribute about 2% of the rolling resistance that the best urethane inline skate wheels produce, so there is very little opportunity in improving speed by spending more money on bearings. Newer bearings on the market have been offered that use ceramic ball bearings instead of steel, which are more expensive than traditional steel bearings but made of harder material.
  Two bearings are used per wheel. The bearings slip into openings molded into each side of the wheel hub, and a flange molded into the wheel hub holds the bearings the correct distance apart. Additionally there is an axle spacer either machined into the axle or that slides over the axle (depending on the axle system used). Since the outer race of the bearing contacts the wheel spacer and the inner race of the bearing contacts the axle spacer, it is critical that the relationship between these two spacers is correct. If the wheel spacer is wider than the axle spacer the bearings will bind when the axle bolt (or bolts) are tightened.
caption: Axles, bearings and spacers
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