Service a wheel hub by removing the wheel and axle nuts, pulling the axle out one side and catching the 9 or 10 balls on each side, cleaning everything, replacing any ball with a flat spot, crack or pit, then repacking the cups about two-thirds full of grease and threading the cone down until it just touches the balls with no play but no binding. Because a quarter turn of a 1 mm thread moves the cone only 0.25 mm, adjust in very small steps, and make sure the wheel is secure in the frame afterward.
Part of Bicycle Repair & Fabrication
Hub bearing service is the disassembly, cleaning, repacking and adjustment of the cup-and-cone ball bearings in a bicycle wheel hub.
Small Turns, Small Clearances
Adjusting a cone is a matter of tenths of a millimetre. A thread of pitch p advances p per full turn. If the axle thread has a 1 mm pitch (an assumed figure; check your own), a quarter turn is 1 / 4 = 0.25 mm. Hub balls are commonly about 4.8 mm across (3/16 inch, a recalled typical size, not checked for your hub; measure your own balls). The correct clearance is so small that one eighth of a turn can change a free-running bearing into a binding one.
Tightening the locknut against the cone usually pushes the cone a little further in, adding some preload. So set the cone with a trace of play before locking, then check after locking, as the feel changes.
What You Need
- Wrenches for the axle nuts, and a thin cone wrench for the cones
- A cup or tray for the balls
- Solvent and rags
- Grease
- Replacement balls of the same size, if any are pitted
Method: Strip, Clean, Repack, Adjust
Step 1: Remove the wheel.
Step 2: Open the hub. Remove the axle nuts and pull the axle out one side, with the loose cone and locknut. Catch the loose ball bearings, usually 9 or 10 per side. Put them in a cup so none are lost.
Step 3: Clean the balls, the cones (threaded cone-shaped pieces on the axle) and the cups (inside the hub) with a rag and solvent (Gasoline is flammable; prefer kerosene or alcohol and keep flames away).
Step 4: Inspect. Any ball with a flat spot, crack or pit must be replaced. Check the cups and cones for pitting.
Step 5: Repack. Fill the cups about two-thirds full of grease.
Step 6: Seat the balls. Drop the balls into the grease; they should sit in the cup without falling out. Use the same count on both sides.
Step 7: Refit and adjust. Slide the axle back in and thread the cone down until it just touches the balls, with zero play but no binding. Too loose causes clunking; too tight causes grinding.
Step 8: Lock. Tighten the locknut against the cone, holding the cone still with the cone wrench. Recheck the feel.
Step 9: Test. Spin the axle between finger and thumb: it should turn smoothly with no grit and no side-to-side shake.
Step 10: Refit the wheel and check it is secured. With axle nuts, tighten both firmly and equally so the wheel is centred. With a quick-release lever, close it so it takes firm hand pressure. Then lift the wheel, push it sideways, and apply the brake while rocking the bicycle to check nothing moves.
Common Mistakes
- Uneven ball counts on the two sides — the bearing sits crooked.
- Locking the cone too tight — it grinds.
- Locking it too loose — it clunks and wears.
- An unsecured wheel — a loosely fixed skewer can let the wheel move or drop out under braking.
Safety
The wheel must be fixed before you ride
A wheel that is not firmly fixed can drop out of the frame under braking or on a bump. After every hub service, check both sides before riding, and test the brake at walking pace. Solvents are flammable: see Bearing Maintenance.
What’s Next
- Learn next: Bottom Bracket — the pedal bearings
- Combine with: Wheel Truing — the wheel the hub sits in