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Q&A: Tires might be humming a wheel-bearing warning

31.12.69

QUESTION: I purchased new tires for my 2003 Focus and have had the tires balanced and rotated every 6,000 or 7,000 miles, a total of four times. This summer I noticed the tires were making a "humming" noise in a kind of off-on-off-on manner. The humming happens only when I'm driving straight ahead. When I go around a curve or make a turn, the humming stops. The tread looks good, and the tires have only 24,000 miles on them. A technician at the shop thought it might be the wheel bearings.

ANSWER: Have the tires rebalanced and rotated once again, making sure the front tires end up on the rear of the vehicle. If this has an effect on the humming noise, the problem is with the tires.

If this doesn't change the noise, the tech may be correct. A front-wheel bearing or hub assembly may be the cause. On most front-wheel-drive vehicles, these are factory-assembled and sealed units that are not serviceable.

Here are two quick checks that can identify a failing hub. Set the parking brake, block the rear wheels and support the vehicle with a jack stand under the suspension. Grasp the tire with gloved hands at the 12/6 position and try to rock the tire and wheel in and out. Any identifiable play in the hub - not in the suspension or steering - is cause for concern. Next, turn the key on but do not start the engine; shift the transmission into neutral and turn the key back to the off position. Carefully grasp the front coil spring with one gloved hand and spin the wheel and tire with the other. Often, a worn bearing in a front hub will generate a resonance or vibration in the spring as the wheel rotates.

Source: Sacramento Bee