Reader Question: My car shakes and vibrates on freeway, does this mean I need a front end alignment?
Dear concerned car owner,
How do you know if your car needs a front end alignment? Vibrations, shimmy, and shaking felt in steering wheel are usually not a sign of needing a front end alignment. A front end alignment, or four wheel alignment as it is commonly referred to these days due to fact that rear end of vehicle can also be adjusted, does just what name implies align, or line up direction of wheels so vehicle is pointed in a straight line.
Caster, camber, and toe are terms used to describe direction of wheel in relation to body of vehicle. The front of tire can be pointed in toward center of vehicle thus "toed in." When front of tire is pointed outward, it is referred to as "toed out." Both of these problems can quickly wear down tread of a tire and can cause a "pull" in one direction of front end. The top of wheel can also lean in toward center of vehicle or lean out away from vehicle, causing a camber problem. This situation can also cause tire wear and a pull to one direction in front end. Caster measures relationship of left and right wheels to each other. If one wheel is farther forward or back from other wheel, then there is a caster problem. Caster will usually not cause a pull or tire wear, and this problem is commonly found on wrecked vehicles.
So what causes shimmy and shakes in front end? The biggest culprit is an out-of-balance or out-of-round tire. As tread on tire wears, it will need to be re-balanced to evenly distribute weight of tire and wheel. To do this, small lead weight is attached to outside of wheel and a machine is used to spin tire and wheel to check balance. Tires should be balanced and rotated every 12,000 miles (approximately every four oil changes) to ensure even tire wear and extend tread life. Out-of-round means tire has worn unevenly and cannot be balanced. An out-of-round tire will have to be replaced. I have even seen new tires that were out-of-round due to a manufacturing defect.