AUTO Q AND A: Car sound raises concern
Question: I took a friend to the airport last week and he commented that the car might have a bad wheel bearing, because there was a whirring sound. I hadn't noticed the noise or maybe was so used to it that it seemed like part of all the normal ...
Question: I took a friend to the airport last week and he commented that the car might have a bad wheel bearing, because there was a whirring sound. I hadn't noticed the noise or maybe was so used to it that it seemed like part of all the normal sounds. How serious is this? Is there a way to be sure he's correct without having the part replaced?
Answer: Sometimes it takes a fresh set of ears or eyes to notice a problem that gradually creeps in. A whirring noise while driving could be caused by several things, with tires and wheel bearings being at the top of the list. Let's start with tires, as they can be a common and easily remedied cause. All-season tires, or those with bold and/or diagonal tread, can become surprisingly noisy with age, especially in wider sizes. The tread may begin to wear unevenly, due to steering forces, alignment issues, worn shock absorbers, deferred tire rotation, or incorrect inflation. Even a tiny amount of tread scalloping can result in noticeable noise. This isn't necessarily a harmful thing, although the cause of rapid or severe wear should certainly be explored and remedied. Low tire pressure can also cause increased tire noise.
Let's check a few things. Try rubbing your hand/fingers across each tire. Does the tread feel uniformly smooth, or perhaps smooth one way and bumpy the other? Is the tread consistent in depth across the width of the tire? Are there depressions or tread injuries? (move the car slightly as needed to see all of each tire's tread) Abnormalities here could be the cause of your noise. You might try rotating the tires (X them if they're not directional tires) and see if the noise changes. If so, it's caused by one or more tires, and likely not a wheel bearing. Adequate but noisy tread can either be tolerated or rectified via tire replacement.
Here's a fairly good check for a faulty wheel bearing: With the tires checked/inflated to the recommended pressure (found on the driver's door edge or nearby body pillar) find a stretch of road that has a sweeping left and right turn that can be safely driven at 25-plus miles per hour (a freeway cloverleaf works well for the right turn). As you vary the steering from straight to turning, and back, is there a noticeable change in the whirring sound? If so, your friend's wheel bearing diagnosis is right on target. If the whirring becomes louder while turning in a particular direction, the outer side wheel bearings (either front or rear) are likely suspects. A noisy wheel bearing may or may not develop noticeable looseness. With the vehicle safely elevated, one can wiggle each suspended tire/wheel. Zero to barely perceptible looseness is OK, more is not. Spinning the tire/wheel by hand and listening/feeling for roughness is another check, but only a really bad bearing may be noticeable. Many times a pitted or rough wheel bearing can only be verified when disassembled and closely inspected.
A noisy wheel bearing should be renewed right away. It's certain to become worse with time, and if severely faulty, can damage other parts or result in wheel instability or separation.