Durable Bicycle Gcr15 Steel Ball Bearing G10 Replacement Bearings Dia: 10mm-30mm

Remove the existing bearing from the hub, bottom bracket, or headset cup and measure its diameter with a digital caliper. Match that measurement to the closest diameter listed in the variant options. For hubs, the bearing diameter is typically stamped on the bearing race or listed in the wheel manufacturer's service manual.

G10 refers to the ISO 3290 grade classification for ball bearing sphericity and diameter variation. A G10 ball has a maximum deviation of 0.25 µm from a perfect sphere, making it suitable for precision bicycle bearing applications where smooth rolling and low vibration are required. Lower grade numbers (G3, G5) are tighter; G10 is the standard for most bicycle service applications.

GCr15 steel is not stainless steel, so prolonged exposure to standing water without lubrication will eventually cause surface oxidation. For wet-weather use, pack the bearing seat with a waterproof grease (such as a lithium-complex or marine-grade grease) after installation. This creates a moisture barrier and significantly extends service life in rain or muddy conditions.

These are loose ball bearings intended for cup-and-cone style hubs and bottom brackets, or any bearing seat that accepts individual balls rather than a sealed cartridge unit. They are not compatible with sealed cartridge bottom brackets (such as press-fit BB86 or threaded BSA cartridges), which use pre-assembled bearing units.

The number of balls per bearing race varies by component. A typical front hub uses 9–10 balls per side (18–20 total), a rear hub uses 9 balls per drive side and 9 per non-drive side, and a cup-and-cone bottom bracket uses approximately 11 balls per side. Check your component's service documentation or count the existing balls before ordering to select the correct pack quantity.

All three pack options contain the same G10 GCr15 steel balls at the selected diameter — the only difference is quantity. The 1-piece option suits a single replacement or test fit. The 5-piece pack covers a single hub side service for most standard hubs. The 10-piece pack is suited for a full hub overhaul (both sides) or stocking a workshop with spares for recurring maintenance jobs.

Yes. Several diameters in the range correspond to common inch-fraction specifications — for example, 25.4mm equals exactly 1 inch, and 19.05mm equals 3/4 inch. If your component specifies an inch diameter, convert it to millimeters and select the matching variant. For non-standard sizes, contact us to confirm fit before ordering.