Bearing Clearance Chart
Radial clearance classes C2, CN (C0), C3, C4 and C5 under ISO 5753-1, tightest to widest, what C0 and C3 mean on a part number, and which FULI supplies.
Radial clearance is the internal gap between the rolling elements and the rings before the bearing is mounted and running. ISO 5753-1 defines five standard classes; this page orders them and shows what the suffix on a part number means. For exact micron values at a specific bore size, request them on the inspection report with your quotation, since the standard’s ranges widen with bore diameter and are easy to misquote from memory.
Clearance classes, tightest to widest
| Class | Suffix on part number | Typical use |
|---|---|---|
| C2 | C2 | Tighter than standard; specialised, low-vibration or precision applications |
| CN (standard) | none, or C0 | General industrial use — motors, pumps, gearboxes, conveyors |
| C3 | C3 | Interference (press) fits, and electric motors where the inner ring runs hotter than the outer ring |
| C4 | C4 | Wider again; heavier interference fits or larger temperature differentials |
| C5 | C5 | Widest standard class; specialised high-temperature or heavy press-fit cases |
Clearance narrows once the bearing is pressed onto a shaft or into a housing, and narrows further as the inner ring heats up faster than the outer ring in service. The class is chosen so the running clearance ends up close to zero, not the clearance before mounting — see the C0 vs C3 clearance checklist for a five-question decision guide.
What FULI supplies
Standard clearance is CN (C0), written on the part number with no suffix. C3 is available on request and should be specified explicitly, for example 6205-2RS C3 rather than 6205-2RS. See deep groove ball bearing and insert bearing for the sizes this applies to.
Send the application and, if known, the fit (interference or looser) to sales@fuli-bearings.com or use the request a quote form, and ask for the clearance measurement on the inspection report if you need the exact micron range for your size.
FAQ
What order are the clearance classes in, from tightest to widest?
C2 is tightest, then CN (also written C0, the standard class), then C3, C4 and C5 progressively wider. Each step up adds more internal clearance before the fit and operating heat take some of it up.
What is the exact clearance in microns for my bore size?
ISO 5753-1 sets a micron range for each class at each bore diameter band, and the range widens as the bore gets larger. Request the clearance measurement on your inspection report at the time of quotation for the exact figures on your size and class.
Does FULI supply C2, C4 or C5?
Standard supply is CN (C0); C3 is available on request for interference fits and electric motor use. C2, C4 and C5 are specialised classes outside FULI's standard range — ask if your application needs one of them.