30308 Bearing Dimensions

Tolerances and fits for 30308

FULI makes 30308 to P0 as standard, with P6 on request. P0 is the Normal tolerance class of ISO 492; P6 limits are tighter. These are the P0 limits for the 40 × 90 × 25.25 mm size.

Δdmp and ΔDmp: deviation of the mean bore and mean outside diameter in one radial plane. ΔTs: assembled width of cone and cup, from the ISO 492 table for metric tapered roller bearings. Cone width B and cup width C: 0 / −120 µm each.

Shaft and housing fits (general guidance)

For an inner ring that turns with a solid steel shaft under normal load, bearing makers’ fit tables give 40 k5 for the shaft of 30308. The cup usually sits in an H7 or J7 housing bore so that it can be moved when the pair is adjusted.

Taking the loosest and the tightest combination of limits, a P0 30308 on a 40 mm k5 shaft has 2 to 25 µm interference. Its cup has 0 to 53 µm clearance in an H7 bore and 13 µm interference to 40 µm clearance in a J7 bore.

This is general guidance, not a FULI specification. Heavy or shock loads, a hollow shaft, a thin-walled, split or light-alloy housing, or a large temperature difference between shaft and housing call for other classes, and the drawing of your machine takes priority.

If the outer ring turns and the shaft stands still, as in an idler pulley or a wheel hub, the fits are reversed: the housing gets the interference fit (for example N7 or P7) and the shaft a sliding one (g6 or h6).

Sources: ISO 492 tables as printed in the NTN catalogue CAT. No. 2203/E (Tables 6.4 and 6.5) and the RKB tolerance catalogue; ISO 286-2 for the seats; SKF and NTN fit tables for the shaft and housing classes.

30308 compared with nearby sizes

30308 measures 40 × 90 × 25.25 mm: bore d, outside diameter D and total width T. Other tapered roller bearings on this site for the same 40 mm shaft are 32008 (40 × 68 × 19 mm), 30208 (40 × 80 × 19.75 mm), 32208 (40 × 80 × 24.75 mm) and 32308 (40 × 90 × 35.25 mm).

32308 is the next heavier choice for a 40 mm shaft, with the same 90 mm outside diameter and 10 mm more width (35.25 mm). In FULI's catalog 32308 has a dynamic load rating of 115.7 kN against 90.90 kN and a weight of about 1.049 kg against 0.748 kg for 30308.

32208 is the lighter option on the same shaft, with an outside diameter 10 mm smaller (80 mm) and 0.5 mm less width (24.75 mm), for housings with less room. In FULI's catalog 32208 has a dynamic load rating of 77.90 kN against 90.90 kN and a weight of about 0.531 kg against 0.748 kg for 30308.

30210 has the same 90 mm outside diameter with a 50 mm bore, so it fits the same housing bore on a larger shaft.

32210 has the same 90 mm outside diameter with a 50 mm bore, so it fits the same housing bore on a larger shaft.

In the 303 series the sizes either side of 30308 are 30307 for a 35 mm shaft and 30309 for a 45 mm shaft.

Cr and weight from FULI's catalog; — = not listed on this site.

30308 weight, load ratings and speed

FULI's catalog gives the weight of 30308 as about 0.748 kg, so 100 bearings weigh about 74.8 kg and 1,000 about 748 kg before packing. The weight is for the cone and cup together.

30308 has a dynamic load rating Cr of 90.90 kN and a static load rating C0r of 107.60 kN. Cr is the load used to work out rating life; C0r is the reference for loads carried while the bearing is stationary or turning slowly.

Values from FULI's catalog; confirm for your application.

30308 cone and cup

30308 is supplied as a complete bearing: the cone (inner ring with rollers and cage) and the cup (outer ring). The total width T of 25.25 mm applies when the two are assembled; the cone and the cup on their own are each narrower. Tell us if you need only the cone or only the cup.

Tapered roller bearings carry radial load and axial load in one direction, so 30308 is normally mounted as one of a pair facing each other, and the end play or preload is set when the pair is adjusted on the shaft. That is why FULI lists the clearance as set during mounting, not as a C-class value.

30308 dimensions in inches

The nearest common inch shaft size to the 40 mm bore of 30308 is 1-9/16 in (39.69 mm), 0.31 mm smaller than the bore, so 30308 would be loose on it. Inch shafts need an inch bearing, not a metric one with a sleeve or shim.

Converted at 1 in = 25.4 mm and rounded to four decimals. The bearing itself is made to the millimetre sizes.

Grease for 30308

FULI supplies tapered roller bearings rust-protected and normally without grease; grease is added when 30308 is mounted. Relubricating 30308 from the side takes about 11.4 g each time by the formula in our grease calculator: 0.005 × D × T = 0.005 × 90 × 25.25.

How FULI supplies 30308

The standard 30308 from FULI has GCr15 chrome steel rings and rollers and P0 precision, with P6 on request. Where an order states a requirement for the total width T (25.25 mm for 30308) or the cone height, each set is checked on a height gauge.

Rings are marked with a brand you are authorised to use, with the FULI brand, or left neutral, as your order states. The box is printed with the model, precision class and brand.

Inquiries that leave out the prefix or suffix letters are the usual cause of a wrong quote, so write the full designation, for example 30308.

Tools and guides for 30308

• Bearing size finder: look up a size from bore, OD and width
• Bearing weight chart
• Bearing grease fill calculator
• Shaft and housing tolerance chart
• Tapered roller bearing number lookup
• Bearing lubrication basics
• Ball bearing vs roller bearing
• How to choose wheel hub bearings
• All bearing products and model pages