Is C3 internal clearance an upgrade that should be specified for every hot-running bearing?

LILY Bearing | 2026-10-28

Best answer

A larger initial clearance can solve one problem or create another

Initial clearance is selected so that the installed bearing has suitable operating conditions after fitting and thermal effects.

Specifying a larger group without understanding those effects does not establish an improvement. JTEKT's clearance guidance discusses both excessive negative clearance and the need to select clearance for the actual application. A hot housing alone cannot show whether initial clearance was insufficient: lubrication, load and installation issues can also affect temperature. Treat a proposed change to C3 as a technical revision with stated reasons and supporting data, rather than a general precaution that is assumed to make every bearing safer.

Review the proposed change against the actual evidence

Record the current complete bearing designation, seat fits, relevant temperatures, speed and load condition.

Ask what observation supports the change and which manufacturer method connects that observation to the proposed clearance group. For example, “the machine feels hot, so order C3” lacks both a measured thermal condition and a clearance assessment. A useful change request identifies the suspected mechanism, the missing inputs and the verification planned after the revision. Keep unrelated changes, such as a lubricant substitution, visible so their effects are not attributed automatically to C3. No particular clearance group is approved by this general review process.