Harry Gibson on February 23, 2023 No Comments
Hearing weird noises from the back of your car? That might just be a bad rear wheel bearing. Not only does it make quite a ruckus when you’re driving, but it’s also potentially dangerous. If you suspect you have a bad rear wheel bearing, we’re going to discuss everything you need to know in this article.
From what it does, the signs that it’s gone bad, the replacement costs, and everything else that’s relevant. By the end, you should be able to make an informed decision before proceeding with any repairs. Here’s a table of contents to help you navigate:
What’s A Rear Wheel Bearing?
If you already know what a wheel bearing is and how it works, you can skip this part. If not, continue reading this section because it’s important that you know how your car works and what various components in your car do. Spoiler alert: the wheel bearing is an important component.
The wheel bearing is a set of lubricated balls or rollers inside a metal ring. This assembly sits at the center of your car’s wheel hub. The wheel hub itself is a round piece of steel (or sometimes aluminum) that has wheel studs so that the car’s wheel can attach to it.
At the center of the hub is a hole for the axle shaft to pass through and connect to the wheels. At the center sits the bearings, which ride your car’s axle or driveshaft to reduce the friction between the shaft and the wheels. This reduces friction between the shaft and the wheels which have several benefits.
First, it prevents the car from making any unpleasant noise when driving. Additionally, less friction means less heat. This prevents excessive damage to both the wheels and the shaft. This design inherently means the wheel bearings support the car’s entire weight, so it gets quite a punishing when driving. Hence why it goes bad after a while.
Each wheel hub in the car has bearings inside them, including the rear wheels. The front and rear designs are usually the same, so anything we talk about the rear wheel bearings in this post generally applies to the front bearings as well. Now, let’s briefly discuss different types of wheel bearings:
Types Of Wheel Bearings
There are four types of wheel bearings, but most road cars use only two of the types. And there’s usually no difference between the front and rear wheel bearings. Here are the wheel bearing types:
- Ball bearings are the most common type as they are effective and cheap to produce. They cope well with cornering pressure, and it generally does the job pretty well. This is what you’ll find in most “normal” cars.
- Tapered bearings are rollers that are slightly tapered to better handle cornering forces. There’s a bit more machining that goes into designing them, hence why they’re more expensive. You’ll typically find this in larger trucks and other heavy vehicles.
- Precision ball bearings are just like ball bearings but they’re higher quality. They produce less friction and heat, rotate faster, and handle cornering forces even better. You’ll find this mostly in race cars, high-end performance cars, and even airplanes.
- Roller bearings have a cylindrical shape and are not used in any motorized vehicle due to their cornering limitations.
While ball bearings are the cheapest of the lot, this doesn’t mean your service bill will be cheap. Your car’s wheel hub’s assembly design will greatly affect the total cost. But we’ll get into the cost later, here are the signs you have a bad rear wheel bearing:
Bad Rear Wheel Bearing Symptoms
First, dishonorable mentions to steering wheel vibrations and the vehicle pulling to one side. Both of these are signs of a bad front wheel bearing, but rarely happen when you have a bad rear wheel bearing. This is because the rear wheels don’t affect steering.
Instead, here are the signs that are more likely to appear when you have bad rear wheel bearings. And yes, they can apply to the front wheel bearings as well:
1. Uneven Tire Wear
Bad wheel bearings can affect your car’s tire wear. This is because wheels with bad wheel bearings tend to wobble side-to-side. This wobble eventually affects your car’s wheel alignment, and when the alignment changes, it can affect tire wear.
For example, let’s say that it’s causing your rear wheel’s camber negative angle to increase. That’s the tilt angle of the tires when viewed from the front of the car. If the angle becomes excessively negative, the inner side of the tires will constantly contact the ground, while the outer side is virtually unused.
This causes excess wear on the inner side of the tire, causing the thread to wear out quicker. Meanwhile, the outer side thread will wear at a slower rate, resulting in uneven tire wear between the inner and outer sides of the tire. Note that uneven tire wear can happen in several ways, depending on how the bad wheel bearings affect the suspension.
The important thing is to take a look at your rear tires and see if both tires are wearing down evenly. Also note that other things can cause uneven or excessive tire wear, including faulty shocks, unbalanced tires, or maybe you just haven’t done a wheel alignment in over two years. You should do a wheel alignment at least every two years.
2. ABS Light
This won’t appear in every car, especially if you have an older car that doesn’t have ABS sensors on the rear wheels. ABS stands for Anti-Lock Brakes, this is essentially a collection of sensors that monitor wheel speed and other aspects and prevents the brakes from locking up during hard braking.
Thanks to the sensors, your car can know when it has a bad wheel bearing. If the sensors detect erroneous readings, it will register a trouble code in the car’s On-Board Diagnostic (OBD) system and trigger the ABS warning light.
You can then scan the OBD system with an OBD scanner, and it’ll return something like a C0210 trouble code. Note that this code can also mean faulty sensors or wires, so you’ll need to match it with the other symptoms.
Again, not every car has this. And if the car doesn’t have a rear ABS sensor, it definitely won’t trigger the light if you have a bad rear wheel bearing. It really depends on your car’s make and model.
3. Wobble Or Play In Wheels
As mentioned, a bad wheel bearing causes the wheel to wobble side-to-side. You can inspect for this wobble yourself by lifting the vehicle off the ground:
- Put the car in ‘Park’ and engage the emergency/parking brakes. Install wheel chocks to the front wheels if you’re only checking the rear wheels.
- Jack up the rear of the car, and then put it on jack stands.
- Rock the wheels front and back. If there’s excessive movement or wobble, this means there’s play and you likely have a bad wheel bearing.
Note that bad tie rods can also cause excessive wobble. And yes, rear wheels also have tie rod-like devices, although they’re usually referred to as suspension links or lateral links.
Anyway, the key difference is that bad wheel bearings create a grinding or humming noise while driving. Meanwhile, bad tie rods or links will usually produce a clunking noise instead, especially when driving over bumps. You can learn more in our guide to bad tie rods.
4. Rear Wheel Bearing Noise
Weird grinding or humming noises will appear when the bearing lost its lubricant or the grease is contaminated. When the bearings go bad, it may leak the grease out of the assembly. Or sometimes the bearings are so old that the grease loses its lubricity.
Whatever the case, without proper lubricant, the ball or roller bearings will directly grind with the steel ring. This increases friction, and heat, and produces a lot of noise. Needless to say, this noise won’t be pleasant to hear while you’re driving.
Rear Differential Noise VS Wheel Bearing Noise
Before we proceed, let’s talk a bit more about that rear wheel-bearing noise. Since we’re talking about rear wheel bearings, the noise will come from the rear of the car. If you have a rear-wheel drive car, you also have the car’s differential at the back.
The differential is a set of gears that controls power distribution and allows for the wheels to spin at different rates. A bad differential will also produce a similar noise when they’ve gone bad because the metal gears inside them will grind against each other.
You can differentiate it by paying attention to how the noise changes. Sounds from a bad rear wheel bearing will change only with speed variations, and sometimes gets worse during cornering. Meanwhile, noises from a bad rear differential change with speed and engine load as well.
For example, if you’re climbing a hill and accelerating hard, the noise from a bad differential will get significantly worse even if you’re not going very fast. Meanwhile, the noise from bad wheel bearings will not change unless the car is going faster.
Also, note that sometimes the noise is mistaken for tire noise. Old tires, thin tire threads, or unbalanced tires can produce more noise than usual. Tire noise also only changes with speed, but tire noise will change depending on the road surface, and bad bearing noise does not.
Causes & Diagnosis
Why do these ball bearings go bad? As mentioned, they take quite a lot of abuse and support the car’s weight, so it’s normal for them to wear out over time. They typically last between 85,000 and 100,000 miles. But there are several reasons why they could wear out more quickly:
- Bad installation that causes the bearings to sit improperly or causes damage.
- Using poor quality or secondhand bearings.
- Poor road conditions such as rough roads put extra stress on the bearings, causing them to wear out quicker. Not taking care when driving through rough roads will worsen the problem.
- Driving through standing water or deep puddles. Doing this often can contaminate the bearings, polluting the grease inside them which causes excess friction and wear.
- Modifications such as bigger or wider wheels and stiffer shock absorbers. This also puts excess stress on the bearing.
Those are the reasons why your ball bearings wear out more quickly. Now, if you want to verify that you have a bad rear wheel bearing, here’s what you can do:
Rear Wheel Bearing Noise Diagnosis
We’ve already mentioned that you can check it by jacking up the car and rocking the wheels to see if it wobbles. But bad tie rods (or links in the case of rear wheels) can also cause this wobble. Here’s how you can differentiate them:
The video above shows how to diagnose the front bearings, but the method is the same for the rear bearings as well. Essentially, what you need to do is to look at the inner side, and pay attention to the links when you wobble the wheels. If the links remain firmly in place, then it’s a bad wheel bearing that’s causing it.
You can also try rotating the wheels, although if you have a rear-wheel drive car, then you’ll need to put the transmission in Neutral and disengage the parking brake to allow the wheels to spin freely. If you hear a metal grinding noise, that’s confirmation your rear bearing is bad.
Note that if the rear wheels don’t spin freely after making sure the transmission is in Neutral and the parking brake is off, you may have a sticking brake. This is when the brake calipers remain in contact with the rotors when you’re not braking, which can also cause a similar grinding noise.
Rear Wheel Bearing Replacement Cost
As mentioned, there are several types of wheel hub assemblies and it will greatly affect the replacement cost. Here are the types and their cost estimates:
- Serviceable assembly means you can take out the wheel bearing out of the hub and replace it. The replacement cost is between $130 and $220 each (including labor).
- Non-serviceable assembly means that you’ll need to replace the entire wheel hub as the bearing cannot be taken out of it. This costs up to $400 each including labor.
- Press-in assembly is similar to serviceable assembly, but you need to machine press the bearing into the wheel hub. This also costs around $400 for each bearing.
Note those are just estimates and for just one wheel. If you’re replacing both bearings on the axle, that’s going to cost at least $260 for a serviceable type. And nearly $1,000 for other types, especially in luxury or performance cars.
So, can you save money by replacing them yourself? Yes, and no. Obviously, the press-in assembly type can’t be a DIY project since requires special machinery. But even the serviceable and non-serviceable types aren’t exactly easy to replace either. This brings us to our next section…
Rear Wheel Bearing Replacement
Replacing the rear wheel bearing is not an easy job. Professional mechanics will need an entire day to replace both sides. And if you’re going to do it at home, chances are it’s going to take an entire day just for you to replace one side. Here’s a quick summary of what the process entails:
- Remove the axle nut if your car’s rear wheels are driven (rear-wheel drive or all-wheel drive). Preferably when the car is still on the ground.
- Jack up the car and remove the wheels.
- Remove the brake caliper and then the brake assembly to gain access to the wheel hub. You’ll need to remove the brake cover and parking brake shoes if you have drum brakes.
- Disconnect the ABS sensor if your car has it on its rear wheels.
- Undo several very stubborn bolts, and remove the wheel hub. Using a slide hammer to pull it out may be necessary.
- Once you got the wheel hub out, you’ll need to either replace its bearings or install the new wheel hub assembly depending on your car’s hub assembly type.
- Replacing the serviceable type usually requires a grinder to remove the old bearing from the hub.
- Reinstall everything that you’ve taken apart so far.
The video above shows how to replace a non-serviceable assembly type on a Subaru. You can see that the process isn’t as straightforward as say, changing a spark plug.
This is considered to be an intermediate replacement job to do. While it’s possible, it will take some time and patience. We’ll let you decide for yourself whether you think this DIY project is worth taking on or not.
Wheel Bearing: What You Need to Know – Facts
- A wheel bearing is a set of steel balls held together in a metal ring, called a race. It helps reduce friction when the wheel spins and supports the entire vehicle’s weight while driving.
- Wheel bearings need to be tight enough to keep away water and road dust as there is no constant source of lubrication for them.
- The most common type of wheel bearings used today is ball bearings. Other types include tapered roller bearings, mainly used for trucks, and precision ball bearings, designed for intense radial loads.
- The warning signs of a bad wheel bearing include an audible grinding or grating noise from the wheel or tire that gets louder as the vehicle accelerates.
- Looseness while steering, pulling, and uneven tire wear are also potential signs of a bad wheel bearing.
- Noise can be misleading, and 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 that changes in proportion to vehicle speed.
- A bad wheel bearing can cause real safety concerns, compromise the smoothness of your ride, and shorten the longevity of your tires.
- It can be dangerous to drive with a bad wheel bearing as it may cause the wheel to stop while driving and put a lot of stress on the hub, the CV joint, and the transmission itself.
- The cost of a wheel bearing replacement is straightforward but may vary if other related issues are discovered, such as having to remove the steering knuckle or replace some suspension components.
Rear Wheel Bearing FAQ
Still, got more questions about your car’s rear-wheel bearing? Here are some answers you might find useful:
How To Replace Rear Wheel Bearing
Replacing the rear wheel bearing will require you to remove the brake assembly, or the brake cover and parking brake shoes if you have drum brakes. Then you’ll need to remove the wheel hub from the steering knuckle by undoing several bolts. And you’ll need to spray it with penetrating fluid, and sometimes use a slide hammer to get the hub of. Afterward, either replace the wheel bearing or the entire hub depending on your car’s wheel hub assembly type. Replacing the entire hub is more expensive, but easier to do. Meanwhile, replacing the wheel bearing is cheaper, but often requires a grinder or a chisel to remove the old bearing.
How To Tell If Rear Wheel Bearing Is Bad
The first sign that you will notice is a grinding, sometimes howling sound from one or more of your wheels. This sound changes depending on the car’s speed, and gets worse as you go faster. Note that if the sound changes when you switch road surfaces, then that’s tire noise. The next way to tell is to lift the car and rock the wheels. If it wobbles, inspect the suspension links behind the wheels. If the links don’t move when you rock it, then a bad wheel bearing is the cause.
How Long Does It Take To Replace A Rear Wheel Bearing
Most professional mechanics will need an entire work day to replace wheel bearings on both sides of the axle. But it may take more depending on how difficult the wheel hubs are to remove. If you’re doing it yourself, it can take a day just to replace one of them. Depending on your mechanical skills and the tools you have at hand.
What Does A Bad Rear Wheel Bearing Sound Like
A bad rear wheel bearing sounds like grinding, sometimes howling noise. The grinding and howling noise usually happen when it’s really bad. If not, it might sound like a really loud wind noise. The key thing is to pay attention if the sound changes with the speed. If it does, and it’s the same regardless of engine load and road surface, then it’s a bad wheel bearing.
How Much To Replace Rear Wheel Bearing
A rear wheel bearing replacement costs $130 to $400 each on average, including labor. This depends on your car’s make and model, the wheel hub assembly type, and labor rates. Luxury and performance cars are likely to cost more.
Rear Wheel Bearing: Wrap Up
To summarize, the wheel bearing is a set of balls or rollers inside a steel ring that rides between the wheel hub and the car’s axle or driveshaft. This reduces friction between the axle and the wheel hub and helps your car to run smoothly.
Like any other moving part in your car, they can wear out over time, usually after about 85,000 miles. Or earlier if it wasn’t installed correctly or the grease inside the bearings has been contaminated.
Replacing a single wheel bearing costs between $260 and $400, but performance and luxury cars are likely to cost more than that. While it’s quite expensive, we recommend leaving this replacement job to professionals.
Replacing a wheel bearing requires skill, time, and patience. And it’s easy to get wrong which can lead to even more problems in the future. Unless you’re absolutely sure about your DIY skills, best to replace it at a trusted auto repair shop instead. Good luck!
