A wheel bearing has a real simple job: It makes sure that your wheel spins freely, without any binding or vibration. A wheel bearing’s goal is to mitigate the effects of friction, which ultimately improves your car’s ability to roll smoothly—all while reducing wear to ensure it’s able to do so for a long time.
A wheel bearing is typically composed of a series of small roller bearings arranged in a circle and encased in a durable shell. The assembly is packed in grease and sealed to prevent excessive moisture and grit ingress. Then, the whole thing slips around the vehicle’s axle or spindle, where it can spin right round, baby.
But given the amount of times it has to keep the wheels spinning really, really fast (and the rain-, dust-, and salt-rich environment it often has to work in), a wheel bearing will eventually wear out. While a failed wheel bearing can be a big problem, the good news is, it’ll probably give you plenty of warning that it’s going bad—you just have to know what to listen for.
How to Tell if Your Wheel Bearing is Bad
The key word above is “listen.” Though you may be able to jack-up your vehicle and check the wheel for movement and play, noise will typically be your first (and best) indicator that you’ve got a wheel bearing on its way out.
It’s always a challenge to describe a noise in text, but a bad wheel bearing will often start out as a “growl,” sort of like a dull, soft grinding noise. It can also be a whine, a hum, or a soft roar. In some cases, bad wheel bearing noise could even manifest as a clunk or squeak.
You may also start to feel it through your steering wheel or in your backside seismograph. Again, a wheel bearing’s job is to ensure your wheel spins smoothly. When it doesn’t, you’ll probably start sensing unpleasant vibration and noise throughout the passenger cabin.
The noise/vibration might only be noticeable at certain speeds, and it may even go away momentarily depending on chassis movement (more on that in a sec). In any event, it’ll likely get worse as the bearing continues its progression towards complete failure, so it’s good that you catch it as early as possible.
Avoid a Wrong Wheel Bearing Diagnosis
But before you point the finger at a wheel bearing, you want to make sure the noise isn’t coming from somewhere else. So here are a few things to consider:
- Make sure your tires are in good shape and properly inflated. Worn, unbalanced, and underinflated tires can mimic the symptoms of a bad wheel bearing.
- Does the noise change when you apply the brakes? Does it stop entirely? Then it’s a good idea to check out your drums/discs first, before going much deeper. In a safe area(!), experiment with some light brake taps, a few hard jabs, and then ride the brakes a bit to see if it affects the noise you’re experiencing.
- Does the noise change with engine speed? Remembering that engine speed and wheel speed often change together, try this: While coasting to a stop on a highway off-ramp, (again, in safe conditions!) shift into neutral. If, when the engine RPM drops, there’s no change in the noise, then the noise is probably linked to wheel speed, which points to a wheel bearing problem. (Once you’re stopped after the test, shift back into drive and be on your way.)
We’ve got a really good article on driveline noises that goes into more detail. Check it out here: Quick Guide to Diagnosing Differential & Driveline Noises
How to Track Down a Bad Wheel Bearing
Now that you know what to listen for. You need to know where to listen for it.
Since a wheel bearing is located at or near the wheel, the noise will probably be coming from one corner of your vehicle—provided you’ve only got one bad bearing, of course.
It’s usually pretty easy to determine if the noise is coming from the front or back, given the driver’s seating position and their proximity to the front wheels. The hard part is often determining whether the noise is coming from the left or right (driver or passenger) side of the vehicle.
But good news there, as there’s an easy test that may help. While it’s not 100% foolproof, if you notice the noise stops while you’re turning—or even slightly veering—then an opposite side wheel bearing is the likely culprit.
That’s because turning shifts the weight off the side of the particular offending wheel. Now unloaded with less stress, the bearing might shut up for a second and be perfectly content. When the vehicle weight shift returns to normal, the bearing is back to being loaded and it’ll start to whine again (sometimes literally).
So pay special attention while turning and, at highway speeds, if you can safely(!) rock the steering wheel slightly left and right to shift the vehicle’s weight to each side, it may further help you diagnose where the noise is coming from.
Again, this isn’t a 100% accurate test, but it can be a big help.
How Long Should A Wheel Bearing Last?
That’s a tough question to answer with a definitive mile threshold. We hear tell of wheel bearings lasting the life of the vehicle, like 200,000 miles and up. Conversely, some cars (cough*old Subarus*cough) seem to go through wheel bearings every few years or so.
It often boils down to both the vehicle and the driving conditions. All-wheel-drive cars put different demands on wheel bearings than, say, front wheel drive cars. Late-model performance cars place stresses on wheel bearings that regular commuter cars don’t. Mud-slinging off-roaders subject their wheel bearings to muck and grit that a street-driven car rarely sees. Make sense?
The takeaway here is that early detection is important. And narrowing it down to the precise wheel can help save you some time and money in diagnostic costs.