Why Wheel Bearings Are Important, And What Happens When They Fail

Wheel bearings are vital in making sure your car’s wheels function as they should - here’s how to tell when one’s dodgy and avoid much bigger issues further down the line
Why Wheel Bearings Are Important, And What Happens When They Fail

There’s a decent chance that at some point, you’ve had your car back from an MOT test and found a patch of orange on the results that says something along the lines of ‘play in offside front wheel bearing.’ It sounds scary - after all, in order of everything you want to function correctly on your car, the wheels are pretty far up the list.

As long as you catch a wheel bearing issue early, though, it shouldn’t be a massively expensive or time-consuming fix, and if you’re decent with a spanner, it’s potentially something you can sort yourself. Here’s what a wheel bearing is, why it’s important, and how to tell if there’s something wrong with one.

Wheel bearings play an important role within the drivetrain of any vehicle, as they provide the first connection between the moving and static areas of the car. A bearing – in its simplest form – is a friction reduction device placed within something like a wheel to aid the efficiency of rotation. This is achieved as rolling produces much less friction force than sliding.

The wheel bearing can be seen just behind the Mercedes logo in this diagram
The wheel bearing can be seen just behind the Mercedes logo in this diagram

A car’s wheel bearing does this by using small metal balls or cylindrical rollers that roll between two smooth rings of metal. Helped along by grease, the bearing rotates in tandem with the wheel’s rotation, the rolling motion of the balls or rollers allowing the wheel hub to rotate as freely as possible. It also helps absorb some of the forces exerted on the car’s wheel during acceleration, braking and cornering.

The wheel bearing is housed within the hub assembly, providing the static connection with the hub carrier through an outer ring or ‘racer’. On driven wheels, the driveshaft travels from the transmission and passes through the centre of the wheel bearing through the inner ring, creating the rotational partnership. Ball-type bearings are generally used on the driven wheels of a vehicle, while tapered roller bearings, with cylindrical rollers arranged around an inner ring, are predominantly used on the non-driven wheels.

A hub assembly which utilises tapered roller bearings. Tapered roller bearings use lateral rollers that taper along with a spindle that the bearing is mounted on, producing an efficient rotation in a slightly different manner than a ball bearing
A hub assembly which utilises tapered roller bearings. Tapered roller…

Like all mechanical parts on a car that rotates, rub and roll, they tend to wear out eventually. There are several signs of a knackered wheel bearing. The most common is a constant drone, hum or growl from the affected wheel, which will get more noticeable as speed increases or the car turns. You may also notice less responsive steering or speed-dependent wheel wobble. On more modern cars, which often have anti-lock brake sensors integrated into the hub assembly, you might get an ABS warning light on the dash.

There are three general causes of a dodgy bearing:

• Incorrect alignment due to poor installation

• A damaged or leaking bearing seal

• An inward collision due to a side impact

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The most common mechanical failure is due to a seal leak, which allows the lubricating grease to exit the bearing, and water and grit managing to worm its way in. This all amounts to the degradation of the balls and the outer and inner housing of the bearing, often creating that gritty, skimming sound as the wheel is rotating. Looking inside a worn-out bearing, there will often be small specs of metal that have broken off from inside the bearing itself and are grinding their way around the racers, causing more damage. If you have had a minor shunt, it’s always worth having the hub assembly checked over afterwards.

Wheel bearings are generally made from hardened steel, so they can withstand a serious amount of rotational abuse. But apply heat (through lack of lubrication) or dirt and water (broken seal) and all hell can break loose (this is yet another reason to avoid driving through deep water). Hitting one too many potholes or taking speed bumps too quickly can also exert excessive force on your bearings, shortening their useful life.

To replace a wheel bearing properly, it has to be popped out of the hub assembly, preferably using a hydraulic press. Problems can arise with the re-installation of the new bearing, as the alignment must be accurate to avoid the bearing wearing out rapidly and causing further pain. 

Wheel bearings should last tens of thousands of miles, but many mechanics will simply hammer the bearing back into the hub assembly instead of precisely aligning it and using the aforementioned press. This will inevitably lead to the bearing not rotating in the perpendicular fashion that it was designed for, accelerating wear and damage to the part. It’s important, therefore, if you’re not 100 per cent confident in your own ability, to ensure you’re using a trusted, professional garage.

A hydraulic press is the surefire method to insert a new wheel bearing
A hydraulic press is the surefire method to insert a new wheel bearing

Most online parts stores will now sell the entire hub assembly with the wheel bearing pressed into it, saving the hassle and potential scope for mistakes within the specific bearing assembly. It goes without saying, but you should also make sure that, if possible, you or the garage is using an original manufacturer part or one of reasonably similar quality - this is one area you really don’t want to skimp on.

If left to wear down further, a wheel bearing could seize and lock the axle, causing all sorts of additional damage to the drivetrain. Worst-case scenario, the wheel may come off the car altogether, so it’s best to get the car looked at as soon as possible if you suspect a dodge bearing. However, considering the forces that a drivetrain has to counteract during its lifetime of usage, it is impressive how long wheel bearings can last if inserted properly and looked after - depending on the car, original bearings can generally last for comfortably over 100,000 miles.

Although it can be a labour-intensive job if one were to fail, the shift to selling entire hub assemblies should make a bad wheel bearing fixable from home, with a decent tool kit and a bit of know-how. So do not fret the next time that horrid whir begins to creep into the cabin, as a fix may be only a ratchet spanner away.



There’s no need to PRESS the issue, we all should now this by now.

12/20/2016 - 17:25 |
2 | 4

These puns are kinda FORCED in every news posy

12/20/2016 - 17:26 |
2 | 2

“What General Motors can’t get right; Part 1 of many”

12/20/2016 - 17:31 |
64 | 0

This article couldn’t be more well timed. Just had to get the bearings replaced on both of my Tahoe’s front wheels.

12/20/2016 - 20:37 |
20 | 0


12/20/2016 - 20:48 |
2 | 0

It could be worse
All your hardware could be rusted out along with your frame COUGH COUGH Ford COUGH

No joke
Literally happened to my truck
Along with just the absolute terrible packaging for working on them

12/21/2016 - 13:33 |
0 | 0

Roadkill episode 2

12/20/2016 - 18:11 |
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Nameless Ghoul

Just a few months ago I’ve had the rear wheel bearings of my E36 replaced. When the mechanic popped them out, he said that the rear right bearing was shot beyond recognition and it was a miracle that it didn’t break.

Which means, that a few months prior, I’ve just hit 210 KPH with broken wheel bearings in what’s essentially a 20 years old coffin on wheels. Yay.

12/20/2016 - 18:16 |
42 | 0

Hey, i have driven a car to the limit where humming sound is so loud inside that you can’t even hear a Radio. They can last a long time before they go, even if they are shot.
Also had an situation where from the moment bearing started to hum, till it disintegrated it self, it lasted about 2 km…. I guess it depends on how good brand you use and how lucky you are.

12/20/2016 - 22:16 |
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12/20/2016 - 18:31 |
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In reply to by Anonymous (not verified)

This is car throttle.. The only thing members need to find for the night are more cars 😂😂

12/20/2016 - 18:51 |
10 | 0
Jovan 1

In reply to by Anonymous (not verified)


12/20/2016 - 19:16 |
0 | 0
Jovan 1

In reply to by Anonymous (not verified)


12/20/2016 - 19:16 |
0 | 0

In reply to by Anonymous (not verified)

Yer not welcome around these parts, ya hear?

12/20/2016 - 19:22 |
0 | 0

How unbearable, those bearings look like Lindor balls all melted up. I’m losing my bearings, I think it’s hazelnut Lindors, but i’m not sure if it’s Dark chocolate or not, or milk chocolate bearing a dark top layer. Bare with me here……….., cuz i don’t really care, I’ll eat them both.

12/20/2016 - 19:47 |
4 | 8
Christian Lepper

Last year I was driving from Townsville to Brisbane. And about 800km in the wheel bearing on the rear right wheel went which shook the wheel completely off. I was only a learner at the time so it was the scariest thing that had happened to me while driving. The worst part was the car had just been serviced for the trip and the bearings had been replaced.

12/20/2016 - 22:04 |
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Austin 3

I feel dumb because I cant figure out how the bearings work with the rotating axle and how it doesnt just spin and the wheel not move.

12/20/2016 - 22:26 |
0 | 0

I was thinking the same thing. Time to ask Engineering Explained.

12/21/2016 - 01:43 |
2 | 0

The axle is directly connected to the wheel the bearing is there only to reduce friction,noise and increase durability.

12/21/2016 - 05:49 |
2 | 0

They are pressed on and off with an interference fit

12/21/2016 - 13:30 |
0 | 0

They never seize immediately. No need to fear. I have a comparison to make. My Skoda had 5 out of 4 changed in its 175 000 km lifetime. Only one bearing failure might have been caused by an accident. My E46 has had the originals for 245 000 km and 13 years. And none of them seems to be on their way out.

12/21/2016 - 01:30 |
2 | 0

I can’t be the only one who cringed when he did up the wheel nuts with the rattle gun am I?
/me shivers

12/21/2016 - 02:15 |
2 | 2


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