1KG Bicycle 45# Steel Ball Bearing G100 Replacement Bearings Size: 6.90mm-8.05mm

Remove the existing balls from your hub, headset, or bottom bracket and measure one with a digital calliper. Match that measurement to the diameter option listed in the variant selector. If the existing balls are worn, consult your bicycle's service manual or the bearing race manufacturer's specification for the nominal ball diameter.

G100 refers to the ISO 3290 precision grade, indicating that the maximum deviation from a perfect sphere (roundness error) is no greater than 0.0025mm (2.5 micrometres). This level of precision is appropriate for bicycle bearing applications where smooth rolling and consistent load distribution are required.

No. These are loose balls intended for cup-and-cone style bearing systems where individual balls sit directly in a bearing race. Sealed cartridge bearings are pre-assembled units and cannot be repacked with loose balls. Check your hub or headset design before ordering.

The count varies by diameter — smaller balls are lighter, so a 1 kg pack contains more of them. As a general reference, 7mm steel balls weigh approximately 1.4g each, yielding roughly 700 balls per kilogram. Larger diameters will yield fewer balls per kilogram. The 1 kg pack is designed to provide a practical workshop quantity for multiple service jobs.

45# carbon steel is not stainless and will oxidise if left exposed to moisture without lubrication. For bicycle applications, always pack the bearing race with a suitable grease before installation. Store unused balls in a dry, sealed container. If your application involves frequent water exposure, consider whether a stainless steel grade would be more appropriate for your use case.

No. All balls in a single bearing race must be the same diameter. Mixing sizes creates uneven load distribution, accelerates wear on the race surfaces, and can cause the bearing to run roughly or fail prematurely. Always replace a full complement of balls with a consistent diameter.

Measure your existing balls with a digital calliper accurate to 0.01mm or better. Match the measured diameter as closely as possible. If the race shows wear, the original nominal size specified by the bicycle or component manufacturer is the correct reference. When in doubt, contact us to confirm the correct size for your specific component.