Understanding
Wheel Bearings

Wheel What?

Wheel Bearings are a set of small steel balls or rollers that support the wheel and allow it to spin freely. Located at the center of the wheel inside the hub, they reduce friction by allowing the hub to roll around the axle instead of against it.
Proper lubrication of the wheel bearings and regular check ups can help them run smooth.

One of the most overlooked yet highly critical parts of the drive-axle and steering assembly are the wheel bearings. Every wheel on your car is attached to a hub and inside this hub is a set of lubricated wheel bearings that allows your tires and wheels to spin freely without building up too much heat. They are engineered to last a very long time, however, eventually they will lose their lubricity, wear out, and need to be replaced. If they break entirely, it can cause a wheel/tire combination to fall off the car while at speed, leading to a very unsafe driving situation.
Prior to 1997, most cars, trucks and SUV's manufactured and sold in the US had an inner and outer bearing on each wheel that is recommended to be serviced every 30,000 miles. As technology improved, newer vehicle were equipped with a "maintenance free" single wheel bearing that was designed to extend the life of wheel bearings without having to be serviced. From time to time, these "indestructible" wheel bearings will wear out and need to be replaced before they break.
There are a few warning signs that are rather simple to recognize indicating a wheel bearing is wearing out and needs to be replaced.

1. Abnormal tire wear
There are many individual mechanical problems that can lead to abnormal tire wear including:
- Under or over inflated tires
- CV Joints
- Struts and Shocks
- Misaligned Suspension

However, one of the most common sources of uneven tire wear is worn out wheel bearings. It's very rare for wheel bearings to wear evenly. As such, if the left tire is showing more wear, it might indicate a problem with the left wheel bearing. However, wheel bearings need to be replaced together; if there is a problem with one side, you need to replace the other wheel bearing on the same axle. If you or a tire technician notice that one side of your vehicle's tires are wearing out quicker than the other, contact a local ASE certified mechanic so they can road test and diagnose the cause of this tire wear. In many cases it can be something different or minor, but you don't want to risk having a wheel bearing break.

2. Grinding or roaring noise coming from the tire area
It's very difficult to detect a failing wheel bearing as it does not happen very often and when they do wear out, it can happen rather quickly. However, one warning sign of a wearing out wheel bearing is a loud grinding or roaring sound that comes from the tire area of your car. This is caused by excess heat that has built up inside the wheel bearing and losing a lot of its lubricity. Essentially it's a metal-to-metal sound that you're hearing. It's also common that you'll hear this from one, specific wheel and not both sides at the same time. Like the above issue, if you notice this warning sign, contact a local ASE certified mechanic as soon as possible so they can diagnose the source of this sound and fix it before it becomes a safety issue.

3. Vibration in the steering wheel
Another common symptom with other mechanical problems in the drive and steering assembly, a vibration in the steering wheel can be caused by worn out wheel bearings. Unlike a tire balance problem that typically shows up at higher speeds, a vibration in the steering wheel thanks to a worn out wheel bearing will be noticed at slower speeds and progressively get worse as the vehicle accelerates.

4. Additional play in the wheels
This is not very common for normal car owners to diagnose. However, if you have the tire jacked up or the vehicle is on a hydraulic lift, you can check this one out yourself. Grab the wheel on opposite sides and attempt to rock it back and forth. If the wheel bearings are good, the wheel won't "wobble". However, if the tire/wheel assembly moves back and forth, this is most likely due to worn out wheel bearings that need to be replaced as soon as possible.
Additionally, if you notice that the vehicle has a hard time rolling while the clutch is depressed or the vehicle is in neutral gear, it can be caused by wheel bearings that are worn out, creating friction and could be failing.

If you experience any of the symptoms above, have the vehicle inspected by a professional technician such as your friends here at Monkey's Mobile Mechanics right away. We can come to you!