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Humming noise when a vehicle is at high speed can be distracting, and depending on the cause, dangerous.
We’ve outlined the most common causes when a humming noise in a car gets louder with speed. We’ve also provided an audio sample of each issue to help you best determine what’s causing the hum.
Humming at High-Speed: Quick Info
|Likely Causes||Bad wheel bearings, tires, alignment, missing wheel weight(s)|
|Breakdown Risk||No, but bad suspension components can be dangerous|
|Repair Expense||Varies, usually well under $1000|
How to Tell the Difference Between a Bad Wheel Bearing and Bad Tire
Bad wheel bearings and bad tires have a similar sound. You can tell them apart in most cases by doing this simple test:
- Drive at the slowest speed it takes to reproduce the humming noise.
- Wiggle the steering wheel back and forth. You’re looking to change the vehicle’s load balance from one side to the other.
- Did the sound change as you moved the wheel? If it did, it’s likely that your vehicle has a faulty wheel bearing. If it didn’t change, it’s likely a tire-related problem.
If you suspect a bad wheel bearing, jack the vehicle up and free-turn each wheel. If one sounds gritty, that wheel bearing will likely need to be replaced.
1. Defective Wheel Bearing
Here’s what a defective wheel bearing sounds like:
A bad wheel bearing can cause a humming sound. If you have a worn wheel bearing the sound will be a little more high-pitched than a tire issue (you can play that sound below).
You can test all four wheel bearings when the vehicle is stationary. Jack up each wheel and spin it freely. If the wheel in question is “gritty” and hard to turn, you likely found the humming sound’s cause.
You can also use the method outlined above, where you rock the vehicle while it’s moving to see if there is a change in pitch. If there is, you’re usually looking at a worn wheel bearing and not a bad tire.
2. Tire Issues
Here’s the sound of a cupped tire:
If your car or truck is suffering from uneven tire wear, you should be able to pick up the noise while driving around 30 MPH with it getting louder as you drive faster.
With uneven tire wear, you may also notice:
- Steering wheel vibration
- Jagged tire surface
- Images in mirrors look distorted at high speed
Wheel Out of Balance
If your vehicle’s wheels are not properly balanced, it can cause a humming noise when driving.
Tires are balanced with wheel weights when a new tire is installed. Balancing corrects any vibration before the tires go on the vehicle. Take a look behind the wheels. You can usually tell if a wheel weight fell off.
See the wheel weight above? They can be on the front or back of the wheel, depending on where they are needed. You’ll likely see the spot where the wheel bearing was.
Tires that are “cupped” or “scalloped” have uneven tread wear across the tire. Run your hand along the tread. If it’s cupped badly enough, you’ll feel the unevenness.
Cupping is usually caused by the following suspension issues:
- Bad shocks/struts
- Bad ball/cv joints
- Poor wheel alignment
If the cupping is on the inside tread, suspect an issue with the alignment.
If the cupping is on the outside tread, it still could be an alignment issue. But, it’s more likely to be a suspension problem. Here’s more from Atlantic Motor car on cupping. Or, you can watch the video below. It picks up at the exact point where you can see what cupped tread looks like.
Large Tire Tread
A humming noise is completely normal if you’ve recently replaced your vehicle’s tires with an aggressive tread.
Off-road and snow tread tires are notorious for making a loud humming sound.
A bad wheel bearing or suspension issues causing uneven tire wear are the two main causes of humming when driving on the highway. Here are some other things that can cause noise while at speed:
- Brakes– If the brakes have worn past their squealers, they’ll make noise at highway speed. The problem is, the noise is AWFUL. It feels like grinding. It can come and go depending on the wheel’s angle and the vehicle’s speed.
- Power Steering– A bad power steering pump can make a humming sound. The only problem is that it should be heard at any speed. You may only be noticing it while the vehicle is moving. Try revving the engine while in Park and seeing if that creates the humming noise.