Diagnosing Tire Vibrations

One of the most common problems is a complaint that the car shakes at a certain speed. Any vibration that feels like a lateral, or side to side shake that is most intense between 10 and 40 miles per hour is a problem with a tire, rather than a bent wheel.

Block the wheels so the car will not roll. Put the car in neutral to allow the tires to rotate.

Jack up the car one wheel at a time. Rotate the tire while looking straight at the tread.

While the tire is turning, stand directly behind the tire and look for a part of the tread to have a lateral shift from side to side in one spot. It is easy to spot, as the tread lines should remain straight as you turn the tire.

If you notice a wavy pattern in a particular spot, you found your problem. This is a separated tire. A tire separates when the tire becomes overheated. The tread is separating or coming loose from the carcass of the tire. Look for obvious things, such as high spots or bumps indicating a separation due to an impact or defect in the tire. Look at both sides of the tire. If no irregularities are present, then proceed to the next tire until you locate the culprit.

A separated tire is a dangerous situation since the tire will go flat or the tread will come off while the car is in motion, and could cause considerable damage or an accident. The only remedy is to replace the tire.

The next possible cause, though not as likely, would be a bent rim. Hitting a curb or a pothole could cause a bent rim. This usually is a bit harder to determine as you have to know how to check for runout. If you don't find a tire problem, then take the vehicle to a tire shop and ask them to check for a bent rim. They will put the tire on a balancing machine.

Another vibration problem is at higher speeds - usually 45 mph and higher. This is always the balancing of the tire. Simply take the tires to a shop and have them balanced.

Remember that as the tires wear down they decrease in weight, hence the balancing changes. It is very important to remember to not over tighten the lug nuts on your wheels. This can do two things - warp the brake rotors causing a vibration and also makes it impossible for you to get the tire off alongside the road should you get a flat.

This covers 95 percent of all vibrations encountered that are consistent. Any vibrations that only occur once in a while or under certain circumstances and cannot be duplicated easily are usually wear related.