Monday, April 11, 2011

Perth's Pointers #2: Feeling the "vibes" you feel them in YOUR car?

My pointer today is about vehicle vibrations, what they are caused by, and what they are not, and what to do about each type should they happen to YOUR car.

First, let's talk about tires. It's good to talk about tires first, because they are the number 1 cause of vehicle vibrations, hands down. Surprised? Let me explain.

The tires on your car or truck are the only part of the vehicle that actually makes contact with the road, and as the tires run over uneven pavement, or those horrible strips of "wake up buzzers" over by the shoulder, there will inevitably be vibrations transferred up through the suspension and steering linkage to the driver. Of course, right? We all know about regular road vibrations, so I won't go any further in explaining those. However, I WILL explain in further detail some of the  OTHER causes of tire and vehicle vibrations, and how you can tell which is which, and what to tell your mechanic when you take the car in for service.

If your car is vibrating when you are traveling at highway speeds, around 55 mph and up, then the most likely cause is out of balance tire and wheel assemblies. The effect is similar to what an unbalanced washing machine does, if one side is too heavy, then it shakes violently, causing the vibration you feel. Tires are inherently not "perfect", even brand new, as differences in the density of the rubber makes them "heavy" on one side, and "light" on another. Wheels, whether made of steel, or alloy metals such as aluminum, are also not "perfect" when manufactured, and therefore require the use of compensating weights to make them as close to perfectly balanced as possible. Also, as the tire wears, some of the weight is of course "removed", and the assembly will again be out of balance. This is why it is recommended to have your tires balanced about every 6000 miles, or every other oil change. If you've had your tires balanced recently, and you feel this type of vibration, it's likely one of the compensating weights has fallen off, and the tires simply need to be rebalanced.

If however the vibration/shaking occurs at lower speeds, for instance, less than 45 mph, then the most likely cause is an out of round tire. "Out of round" is exactly what it sounds like, a tire that is not completely round, and therefore is traveling down the road with a sort of "bump" to it, in some cases it literally DOES have a bump in it, making the vehicle buck and bounce like a bull in a rodeo. The best thing to do is to have your tires inspected for signs of abnormal bumps, lumps, or evidence of tread separation, which is a condition in which the radial belt (the metal "wire" inside a tire that is designed to make it hold its shape) has broken, slipped, or otherwise come out of place causing the tire to become out of round. I cannot stress enough how DANGEROUS a condition this can be, a tire with a separated belt is like a ticking time bomb, it could blow at any moment. So if you feel a bump, bump, bump while driving at low speeds, take your car to be inspected for tire trouble as soon as possible.

Another cause of tire vibration is abnormal wear. If a vehicle's alignment has moved out of the manufacturer's specified limits, it will cause the tires to contact the road at other than normal angles, causing them to wear unevenly. This can be caused by loose or worn suspension or steering parts, or from carrying excess amounts of weight in the vehicle for extended periods of time. Typically this will cause the tires to be "noisy", rather than being a vibration, and can be described as a rhythmic humming or "buzzing" sound, but depending on the vehicle, it can be perceived as a noise, or a vibration, or both. Tire noise will tend to continue to increase in pitch and volume as the vehicle's speed increases. Most often, if there is abnormal wear, it is visible to the naked eye. As discussed earlier, with the "loss" of tire rubber, whether through normal or abnormal wear, the weight of the tire changes, so there will most likely BE an accompanying vibration, as well as a noise. What is important to understand here is the difference between "normal" out of balance tires, and ones that cause a vibration due to abnormal wear.

I must stress at this point that although a bad or loose suspension part will cause the vehicle to become misaligned, it is NEVER the direct cause of a vibration or shaking in the steering wheel. When the alignment has gone out of the manufacturer's specifications, it causes the tires to wear abnormally, which THEN cause the vibration or shake. The vibration is the effect, NOT the cause. Your suspension could literally be worn out to the point of losing structural integrity, and it would NOT cause a vibration when driving, but it could make a heck of a lot of noise.

Let me give you an example. You're driving one day and you hear a popping sound when you turn to the right. You drive for a few months this way, I mean it's just a small pop, right? Well, all that time, your outer tie rod has been worn, and has thrust the alignment far enough out of specifications that it's torn up the left front tire. The abnormal wear on that tire then causes it to vibrate, and now you have the original noise, AND a vibration. The bad part caused the tire to wear out abnormally, causing a vibration in that tire. The bad part is not the direct cause of the vibration, it's the effect it had on the tire that caused the vibration. 99.9 percent of all vibrations felt on a car are caused in the same manner. Therefore, if you hear a noise, a pop, a knock, a rattle, a squeak when hitting bumps or when turning, they indicate that you probably have a loose or broken suspension part. Left unchecked, they may eventually cause you to feel a vibration, because of the damage the bad part does to your tire, but under NO circumstances are they the direct cause. Remember, it's the tires that cause vibrations.

Many suspension parts have rubber components to allow them to bend and rotate under normal driving conditions, but when they wear out, and metal grinds against metal, the resulting sound can be very loud, and make one feel as though the front end is "falling out". The reason the noise is so loud is that the sound, traveling along the various metal pieces and parts under the car, causes a sort of "amplification" effect. This effect can also make a noise appear to be coming from a different area on the car than is its actual source. Rest assured however, a mechanic with the proper training and tools will most often be able to find the problem easily, as long as YOU, the driver, provide him or her with all the information you can about the nature of the sound and when you hear it. Seemingly insignificant info can mean the difference between him finding the problem, or searching for literally days to hunt down a "phantom" squeak. Did you hear it only early in the day, when you first started driving? Was it only heard on hard left turns? Tell him that. Does it happen only when you have a passenger with you in the car? Did you hear it only on a particular road? Every situation is different, so be aware that while in general, a noise in the front end may indicate a problem with your suspension or steering components, there are other possible causes, so don't assume anything. It's best to have your car checked by a mechanic when you hear anything out of the ordinary, as many issues if diagnosed early can prevent costly repairs later.

To sum it all up, a vibration (or noise, or both) in your car can be unnerving, but generally speaking, it is easily diagnosed, by giving your mechanic "good" information. For instance, at what speed did you feel it? Where in the vehicle did it seem to originate? What were the driving conditions on the road at the time you felt it? Is there only a vibration, or a noise, or both? Were there different conditions you were driving under than normal? Also, tell them things like when your tires were last balanced, and if any components were replaced, as all of these things will allow him or her to more easily pinpoint the cause, and ultimately the solution to your vibration woes, and get you back on the road quickly, again running smooth and straight.

That's my pointer for today, and I hope to see you next time, when I talk about computer viruses, is your PC infected?

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