Go-kart axle bearings: 30 x 62, 40 x 80, 50 x 80 and 50 x 90 mm, and what C3 means

Our go-kart axle bearings come in four sizes: 30 x 62 mm, 40 x 80 mm, 50 x 80 mm and 50 x 90 mm (bore x outside diameter). All four are listed with C3 clearance, ZZ shields and high-speed PS2 grease. Match the axle first, then the outside diameter: a 50 mm axle can take either of two.

Know your axle and the old bearing's outside diameter? Find the row and you're done.

Source: our product listings, checked 12 October 2026. Every bearing in the table is listed as C3, with ZZ non-contact shields and high-speed PS2 grease.

Which kart axle bearing fits: axle first, then outside diameter

The bore of a kart axle bearing is the axle diameter, so a 30 mm axle takes our 30 x 62 mm bearing and a 40 mm axle takes our 40 x 80 mm bearing. Our listings say so in plain words for the 40 mm and 50 x 80 mm bearings: "Fits: Kart with 40mm Axle" and "Fits: Kart with 50mm Axle".

A 50 mm axle is where it splits. We list two 50 mm bearings:

• the SB208ZZ-50, 50 x 80 mm. It shares its 80 mm outside diameter with our 40 mm SB208ZZ;
• the SB210ZZ, 50 x 90 mm.

Both fit a 50 mm axle, but only one fits the hanger or carrier your old bearing came out of. So measure the old bearing's outside diameter, or read the number off its face, before you order.

1. Measure the axle, or the old bearing's bore: 30, 40 or 50 mm.
2. Measure the old bearing's outside diameter: 62, 80 or 90 mm.
3. Find the row in the table above.
4. Check the width. Our listings don't give the width, so if yours matters, send us the old bearing's number and its width and we'll check it for you.

If your axle or outside diameter isn't in the table, it isn't a kart axle bearing we list. Send us the number on the old bearing.

What C3 means on a kart bearing

C3 is a clearance code. It means the bearing has more radial internal clearance than normal: a little more room between the balls and the rings.

That room shrinks once the bearing is running: the outer ring normally runs 5 to 10°C cooler than the inner ring, so the inner ring grows more and takes some of the clearance away. One bearing maker's selection table lists C3 for jobs that allow for shaft deflection and fitting errors.

Every kart axle bearing in our range is listed as C3, in the title of each listing. If you're comparing ours with an old bearing, look for the C3 next to its number. Our bearing seal codes guide explains how the clearance code sits alongside the seal code.

Shields, grease and how they lock on

• ZZ shields. Each bearing has ZZ non-contact shields, which our listings describe as "free spinning". A ZZ shield is a metal shield that doesn't touch the inner ring. The seal codes guide compares ZZ with rubber 2RS seals.
• PS2 grease. They come packed with high-speed PS2 grease, which our listings describe as a synthetic-oil based grease for high-speed, low-temperature use. For relubrication, or anything else you put on the bearing, follow your kart or chassis maker's instructions.
• Grub screws. Our supplier tells us kart bearings lock onto the axle with grub screws.

Our listings say all parts need to be fitted by a licensed technician. For fitting and setting up the axle, follow your kart or chassis maker's procedure, or have a kart mechanic do it.

Trolley and garden kart wheels. Our PFA136-1 wheel bearings, a pack of 4 listed as 3/4" x 1-3/8", name trolleys, garden karts and go-karts among their uses.

Not in our range

• Kart bearing hangers, carriers and cassettes. We list the bearings, not kart axle hangers. Our pillow block and flange units (UCP, UCF, UCFL and take-up housings) list go-karts among their uses. They're sold with UC insert bearings; to check whether one suits your kart, send us your old bearing's number. See UCP vs UCF vs UCFL for those units.
• Kart front spindle and wheel bearings. We don't list kart-specific front wheel or spindle bearings (our PFA136-1 wheel bearings name go-karts among general uses). Read the number on the old bearing and look it up in our bearing size chart.

Which Bearings Express go-kart bearing fits

• Pick the set of 2 SB206ZZ kart bearings, 30 x 62 mm for a 30 mm kart axle.
• Pick the 3x SB208ZZ kart bearings, 40 x 80 mm for a 40 mm axle.
• Pick the 3x SB208ZZ-50 kart bearings, 50 x 80 mm for a 50 mm axle whose old bearing measures 80 mm across.
• Pick the 3x SB210ZZ kart bearings, 50 x 90 mm for a 50 mm axle whose old bearing measures 90 mm across, or the single SB210ZZ to replace one.
• Pick the 4x PFA136-1 wheel bearings for a trolley or garden kart wheel that takes a 3/4" x 1-3/8" bearing.

All our kart axle bearings are in the go-kart bearings collection.

Questions people also ask

What bearing does a 30 mm go-kart axle take?

In our range, the SB206ZZ kart bearing: 30 mm bore, 62 mm outside diameter, C3, sold as a set of 2.

What size bearing for a 50 mm kart axle?

Either 50 x 80 mm (our SB208ZZ-50) or 50 x 90 mm (our SB210ZZ). Measure the outside diameter of the old bearing to tell which.

Do go-kart bearings need lube?

Ours come packed with high-speed PS2 grease and ZZ shields. For any relubrication, follow your kart or chassis maker's instructions.

Related reading

• 2RS vs ZZ bearings: what the seal codes mean
• UCP vs UCF vs UCFL: pillow block or flange bearing, which housing do I need?
• Bearing size chart 6000 to 6310: bore, OD and width

Sources

• NTN, Bearing Units, Cat. No. 2400/E, technical data: 5.3 Bearing internal clearance and 5.3.2 Internal clearance selection (p. 31), Table 5.12 "Examples of applications where bearing clearances other than normal clearance are used" (p. 32), ntnglobal.com/en/products/catalog/pdf/2400E_03.pdf, read 12 October 2026.
• SKF, Deep groove ball bearings: Designation system (skf.com/us/products/rolling-bearings/ball-bearings/deep-groove-ball-bearings/designation-system), read 2 October 2026.

Checked against the NTN Bearing Units catalogue, the SKF designation system, our supplier's advice and Bearings Express product listings on 12 October 2026.