• Bad wheel bearings make humming or unusual noises.Old car weel image by Tomasz Nowicki from Fotolia.com
  
  Wheel bearings perform several important functions in the mechanism of a car. First, the bearings hold the weight of the car. Second, they enable the wheels to spin without interference. All car wheels have bearings. Rear-wheel drive cars, however, may have more problems with rear bearings as they are consistently under more pressure.
  
  

Humming

• Unusual noises coming from rear wheels may be a sign that there is a problem with the rear wheel bearings. Worn and uneven surfaces of the bearings cause a humming, droning, scraping or squeaking sound. Bearings that are not properly maintained can dry out, causing the noise that is emitted. Check this out by driving the car and turning a corner. Listen for noises coming from the wheel bearings to determine if the bearings are bad.
  
  

Steering

• Bearings play a crucial role in assisting with the rotation of the car's wheels. Therefore, they can affect the steering mechanism within the car if they are damaged. If water has entered the bearing through a broken seal, then it may cause the car's steering to change. A symptom of this is imbalanced steering. When the car is traveling forwards in a straight line, bad bearings may cause the steering to drag off-center or wander.
  
  

Loose Movements

• A symptom of bad rear wheel bearings is loose movement of the wheel. You can identify this problem by jacking the wheel up and then wiggling the tire. Raise the wheel at least an inch off the ground, then hold the top and bottom of the tire and move it backwards and forwards. If the rear wheels have bad bearings, the wheels will have a lot of give or movement when you move them. If you're uncertain, perform the same test on the front wheels and make a comparison. While the vehicle is jacked up, manually spin the wheel. A rough rotation is symptomatic of bad rear bearings. The wheel may also make grinding sounds.