A wheel bearing is exactly what it sounds like, it's a bearing for a wheel. What's a bearing you ask? It's a bunch of steel balls held together by a metal ring, which is called a race. There are many different styles bearings but are all very similar and all do the same job, they help something spin with very little friction like a wheel, turbine, or a carnival ride.

 

A [wheel bearings] on a car is a set of ball bearings that support the wheel and ride on a metal shaft which is called an axle shaft. The wheel bearing is located at the hub, the hub is located at the center of your wheel, when you are looking at a wheel on a car, the hub is located where the lug bolts come through the wheel. The lug bolts are pressed into the hub, and the wheel bearing is pressed into the hub as well, from the back side of the hub.

 

Wheel bearings are use on all kinds of vehicles from bicycles to aircraft and they all perform the same job, they allow the wheel to spin freely. Depending on the application, most wheel bearings are hardened steel and will withstand a lot of abuse. A wheel bearings worst 2 enemies are heat and water. Heat caused by lack of lubrication can destroy a wheel bearing, and water that penetrates the sealed bearing will destroy the wheel bearing as well.

 

Most wheel bearings manufactured today are sealed bearings, they come from the factory pressed together as an assembly, front race, bearing set, center race, bearing set and outer race with seals on both front and rear race. Bearings are sealed from the elements, water, and debris by a non penetrable seal that also seals in high temperature wheel bearing grease. When the seal is broken or damaged, the wheel bearing will fail and start making noise

 

A wheel bearing noise gradually becomes louder with time and with speed, what I mean is when the seal is broken or damaged, the wheel bearing will not just start making a loud noise. At first, it will be a very faint noise and within a month, it will be very noticeable. When the wheel bearing is making a noticeable noise, the noise will be more obvious at faster speeds.

 

The noise that a wheel bearing makes is like the noise that your tires make when hitting a rumble strip on the highway, just not quite as loud, same noise at an 1/8 of the volume, or like the sound of playing cards in your bicycle spokes, remember that noise? It's a rotating noise and it will gradually get louder in time. The only fix for damage wheel bearing is to replace it. If a bearing is noisy, repacking it with grease will not make the noise go away.