Which statement describes sleeve bearings relative to ball/roller bearings in terms of friction?

• A. They have a higher coefficient of friction than ball/roller bearings
• B. They have the same coefficient of friction as ball/roller bearings
• C. They have a lower coefficient of friction than ball/roller bearings
• D. They are frictionless

Answer: (D)

Friction behavior in bearings hinges on how the surfaces contact each other. In a sleeve bearing, the shaft slides against the bearing surface, so the contact is sliding. Even with lubrication, sliding contact tends to produce more friction than rolling contact. Ball and roller bearings use rolling elements that carry the load by rolling, not sliding, which greatly reduces friction and wear. Because of that, sleeve bearings do not have lower friction than ball/roller bearings; they typically have higher friction under similar conditions. They also are not frictionless—there’s always some friction, even in well-lubricated plain bearings, whereas rolling-contact bearings usually offer the lowest friction.