Verified by Rachel Mayfield, Supply Chain Analyst - August 2026
The 30208 is a single-row tapered roller bearing with a 40 mm bore, 80 mm outside diameter and 19.75 mm overall width. The dimensions come from ISO 355 and DIN 720, so a 30208 from SKF, FAG, Timken, NSK, NTN or Koyo is dimensionally interchangeable. Unlike a ball bearing, the 30208 is separable: the cone (inner ring with rollers and cage) and the cup (outer ring) come apart and are fitted separately.
30208 bearing dimensions
| Property | Value | Standard |
|---|
| Bore diameter (d) | 40 mm | ISO 355 / DIN 720 |
| Outside diameter (D) | 80 mm | ISO 355 / DIN 720 |
| Overall width (T) | 19.75 mm | ISO 355 / DIN 720 |
| Cone (inner ring) width (B) | 18 mm | ISO 355 / DIN 720 |
| Cup (outer ring) width (C) | 16 mm | ISO 355 / DIN 720 |
| Bearing type | Single-row tapered roller bearing | ISO 355 |
T, B and C: three widths, commonly confused
Tapered roller listings quote three widths and mixing them up leads to wrong orders. T is the overall assembled width of the 30208 - 19.75 mm - and is the figure that matters for the stack-up in a hub or gearbox. B is the cone width (18 mm) and C is the cup width (16 mm). Because the rings are offset when assembled, B and C are both smaller than T and they do not add up to it. When a listing quotes a single width for a 30208, check it is 19.75 mm - a listing showing 18 mm is quoting the cone only.
Cone and cup: fitted separately, replaced together
The cup presses into the housing and the cone assembly slides or presses onto the shaft. That separability is what makes tapered rollers convenient in wheel hubs - each part is drifted in on its own. Replace cup and cone as a set even though they are sold separately in some trade counters: running a new cone against a worn cup transfers the old wear pattern straight into the new part.
Adjustment: tapered rollers are set, not just fitted
A single tapered roller bearing cannot control a shaft on its own - it only takes axial load in one direction. The 30208 is almost always mounted opposed to a second tapered bearing, and the pair is adjusted at assembly: the clamping nut or shim pack sets the running clearance (end float) or preload. A classic trailer-hub setting is to tighten the axle nut while rotating the hub until it just binds, then back off to the first split-pin slot. Gearbox and pinion applications use a measured preload instead - follow the equipment maker's figure, not a generic one.
Brand interchange for the 30208
The 30208 number is used unchanged by every major maker: SKF, FAG (Schaeffler), NSK, NTN, Koyo and Timken's metric range all supply a 30208 with identical boundary dimensions. The one trap is Timken's imperial ranges - designations such as LM11949/LM11910 are inch-series bearings with their own dimensions and do NOT interchange with the metric 30208 even where the sizes look close. Match the full designation, then check 40x80x19.75 mm.
Load ratings: check the maker's catalogue
Dynamic and static load ratings for the 30208 differ between manufacturers and ranges, so MLC does not publish a single figure. SKF, Schaeffler medias, Timken, NSK and NTN all publish free catalogues with per-variant ratings, limiting speeds and the axial load factors that matter for tapered rollers.
Where the 30208 is used
Tapered rollers carry combined radial and axial load, which is why they own the wheel-hub and gearbox world. Typical 30208 applications include car and van wheel hubs, gearbox mainshafts and winches.