Automotive Wheel Bearings
The wheel bearings are the most important components in your car's suspension. They are mostly fixed inside the hub, or in some cars in the brake drum or rotor. Its function is to ensure that the wheel rotates freely. Your car would usually have a pair of bearings for each wheel - the outer and the inner bearing.
One of the main reasons for problems with wheel bearings is due to wearing. Sometimes, the oil seal protecting the bearings can get infiltrated by dirt and debris, and this can damage the bearing and race. In other cases, long-term wear can hamper the bearing from working properly. In extreme cases, when the bearing is not repacked in time, it can break down and the car can come to a standstill. Even the wheel can become disoriented and it can also render the brakes non-working.
If you don't have the prowess of a mechanic, how are you going to find if the bearings have some problem. One sign is the emission of rubbing sound from the car when in motion. The sound would get louder as you increase the speed. Another sign is some jerky movement in the suspension or vibration in the suspension. You can make it easier by jacking up the car and pushing the wheel. If it shows too much movement on the spindle, it is a good sign that the bearing has some problem.
Make sure that you repack or replace the wheel bearings once every 20,000 miles. The job is extremely easy. The only difficult part is that it takes some time to take out the wheel and the brakes. You would have to check the bearing for any signs of scratches or wearing before you clean it and load with some good amount of grease.
If the wheel bearing gets broken down, your car would be extremely difficult to control. If you think that the bearings have some problem, it would be best not to drive your car until you have fixed it. You can always check the wheel bearings to ascertain if they require repacking. Usually, wheel bearings would have pairs of outer and inner bearings. They enable the wheels to move freely over several thousands of miles by providing cushion to the contact between the wheel and spindle.
The wheel is supported on the spindle by the bearings. The bearings are heavily greased so as to ensure that there is no friction between the two surfaces. But, as time progresses, the grease is going to get covered in dirt and even metal particulates. Most of the time, the 4-wheel drive car would have all the wheel bearings sealed. In the case of a rear-wheel or front-wheel drive car, the bearing in the non-powered wheel would usually be repackable. However, the bearing in the powered-wheel may be sealed. This means that you should seek professional help when it comes to repacking these bearings.
So, prior to checking the wheel bearings, it would be better to look into the owner's manual to check if the bearings are sealed or not. In case, they are sealed, then it is not possible for you to repack them. If your car has drum brakes, you would have to check the bearings when checking the brakes so as to ensure that the grease has not fouled. In case, it has been fouled, the particles are going to cause abrasion and wear away the contacts, which can cause lead to noise and a feeling of grinding when the car is running. If the grease has been fouled extremely, it is also possible that you may lose the wheel. In case, the bearings appear to be cruddy, you can repack by yourself.
You would have to jack up the car and support it with jack stands. Try to rock the wheel by holding it from the top and bottom. However, take care that you don't get under the car. If the bearings are good, then there is going to be minimal amount of movement. If the wheel moves a lot, then it is a clear indication that the wheel bearings are worn out and need to be either adjusted or replaced.