Cones are what hold the bearings in a hub. They are screwed onto the axle and provide the interface between that and the hub.

When the cones are too loose the wheel will wobble around on the axle. This can cause the axle to bend, and it can let the bearings get dirty.

[edit] Tools needed

• Cone spanner (example here)
• Spanner for the retaining nut, adjustable will do

[edit] Procedure

First loosen off the nut that holds the cone in place (outside of it on the axle). This will allow the cone to be turned.

Tighten the cone so that the wheel will spin freely without wobbling. If you tighten the cone too much there will be a 'gravelly' feeling and the wheel will not spin freely.

Once the cone is the correct tightness, move the retaining nut up to the cone. Hold a spanner on the cone so it is unable to rotate and then tighten the retaining nut so the cone can no longer move in or out. Do this for both sides.