Practical answer
Interference fits normally reduce internal clearance after mounting. If the inner ring runs hotter than the outer ring, operating clearance may fall further. Selection therefore concerns the clearance in service, not only the unmounted initial value.
C4 normally provides more initial clearance than C3, but suitability depends on shaft and housing fits, temperature difference, speed and load. Replacing normal clearance with C3 or C4 without calculation can increase noise, vibration or premature wear.
On-site checks
- Retain the original C2, C3 or C4 suffix
- Confirm actual shaft and housing tolerances
- Record the likely temperature difference between rings
- Check speed, load, vibration and noise requirements
Record for enquiry or analysis
- Complete original designation and manufacturer
- Shaft diameter, housing bore and tolerances
- Stable and maximum operating temperature
- Any overheating, seizure, looseness or abnormal noise
Suffix rules and allowable values vary by manufacturer. Confirm the final selection against current manufacturer documentation and actual machine conditions. Reference entry points:NSK · Schaeffler medias