Wheel bearings are a set of small steel balls or rollers that support the wheel and allow it to spin freely. Located at the center of the wheel inside the hub, they reduce friction by allowing the hub to roll around the axle instead of against it. Proper lubrication of the wheel bearings and regular check-ups can help them run smoothly. Unusual noises such as clicks, rumbles and groans that change with speed could mean the bearings are worn. An inspection may be necessary. Ask your service advisor to have your wheel bearings checked when the brake pads take longer than normal to kick in, or if you hear grinding noises while driving. Damaged bearings generate large amounts of heat that could cause the wheel to lock up. If the wheel bearings get damaged, they are not able to help the wheel rotate smoothly. If bad wheel bearings are not replaced in time, the locked wheel can come off and cause quite a bit of damage. From a safety standpoint there is a large risk, because a wheel coming off can cause accidents. From an environmental point of view, there is no impact from wheel bearings.