You already know that your car cannot function safely or properly without good, sturdy wheels. What you may not know is that the wheel is far from a simple component. Actually, there is a lot of complexity that goes into the design of a wheel, and several components that must all be integrated together.
A good example of this is the wheel bearing. Wheel bearings are critical for your wheels to work together—specifically, for the hub, tire, and assemblies to work harmoniously. They are also prone to abuse, which is why it’s essential to know the warning signs. But before we go deeper into bad bearings, symptoms, impact, and costs, it’s equally important to understand what it is.
A wheel bearing is a set of steel balls held together in a metal ring, called a race. At the center of your wheels, there is a hollow piece of metal, called a hub. The wheel bearings fit tightly inside this hub, and ride on a metal axle shaft, helping reduce friction when the wheel spins.
These are different from the engine bearings, as there is no constant source of lubrication for the wheel bearings, which means they need to be tight enough to keep away water and road dust. They also support the entire vehicle weight while driving, which is why they suffer a lot of abuse from rough roads, potholes, as well as lateral forces when turning.
As with most automotive components, the wheel bearing can eventually give way to wear and tear, and may even need to be replaced. How will you know when it’s time for a wheel bearing replacement or at least have your vehicle looked at by an automotive professional? Pay attention to some of the key warning signs of a bad wheel bearing.
Ball bearings are the most common type of wheel bearings used today (along with roller bearings—though the latter don’t have the versatility of the ball ones). Other types include tapered roller bearings, mainly used for trucks, and precision ball bearings, designed for intense radial loads. Regardless of the type your vehicle has, the warning signs are the same, specifically a bad wheel bearing sound.
Here are just a few things to keep in mind:
There are many sounds coming from a vehicle that are reason for concern, so it’s important to differentiate between them in order to avoid misdiagnosis. Noise can be misleading: a humming noise while driving can be caused by several different issues, starting with your tires, but it can also be the wheel bearing or CV joint.
The classic sounds of a bad wheel bearing are cyclic chirping, squealing and/or growling noise. You can also tell that the sound is related to wheel bearings if it changes in proportion to vehicle speed. The sound can get worse with every turn, or it can disappear momentarily.
Howling noise that solely occurs during deceleration is a pretty good indicator of loose pinion-bearing preload. If the howling happens under acceleration at different speeds, then it’s probably worn out gears. However, overly worn out bearings tend to make a howling noise as well, when they don’t support the gears correctly. They also tend to make a rumbling sound when turning.