A wheel bearing is an essential part that connects the wheel to the axel. In this article, we’ll detail the role of wheel bearings, the signs they need replacing, and the cost of replacing them.
What are wheel bearings?
Wheel bearings are friction-reducing devices designed to reduce friction between moving parts while allowing the parts to rotate freely. Because they facilitate motion with less resistance, bearings are used extensively in cars, bicycles, engines, aircraft, and other intricate machines. A simple and ingenious device, the wheel bearing plays a vital role in keeping our modern world (and your vehicle) on the move.
Wheel bearings are part of the wheel hub assembly that connects the wheel to the axle spindle. An automotive wheel bearing is composed of an outer race, inner race, and rolling elements – either in the form of balls or rollers. Modern wheel bearings are typically sealed to prevent water and debris from entering the assembly. The seals also keep the grease inside the bearing assembly, which helps the bearings stay lubricated and cool.
What is its purpose?
The main purpose of the wheel bearings is to allow the wheel hub to rotate freely on the axle spindle. They act as an essential link between the stationary and moving parts of the vehicle. Bearings are indispensable in automobiles since intense friction can cause severe damage to the vehicle’s drivetrain and suspension components. Parts that are constantly under load and in motion cannot rely on a thin film of lubricant alone.
Additionally, wheel bearings allow the torque from the axles to be transferred to the wheels with little loss of power. Friction is a waste of motive power, and its reduction is paramount in enhancing the efficiency of the vehicle.
Finally, bearings keep your vehicle stable by keeping the wheels within their axis of rotation and at the same time absorb radial and axial forces.
What are the signs of worn wheel bearings?
There are several signs of worn wheel hub bearings. Some signs are easy to notice, like unusual noises. Some are perceivable only when the vehicle is in motion. Modern vehicles have a diagnostic feature that will alert you to any issues related to your vehicle’s wheel hub assemblies. This feature is really handy – the onboard computer will notify you of any issues before they become severe.
If you’re driving an older vehicle or if your onboard computer fails to send out a warning, the following signals can indicate worn wheel bearings. It’s essential that you take your car for repairs immediately if you encounter any of these signs. Otherwise, you could end up facing costly repairs, and worse, major safety issues.
1. Uneven and abnormal tire wear
The easiest way to spot bad wheel bearings is to check for an abnormal tire wear pattern. A few issues can cause unusual tire wear patterns, including over- or under-inflation, improper alignment, worn suspension components, among others. In the case of bad wheel bearings, you’ll usually notice patches, scalloping, and unusual wear on the tire shoulders.
2. Vibrating or wobbling wheels
Wheel wobbling and vibrations are usually caused by bad alignment, loose wheels, or worn suspension components. However, a gap or play in the bearings may also cause the wheel to vibrate and wobble. Oscillation can vary in severity, usually increasing in parallel with speed. Wobbling contributes to abnormal tire wear, as well.
3. Clicking, grinding, or rumbling
Unusual noises are commonly associated with the bad hub assemblies, worn tires, and damaged suspension parts. However, clicking, grinding, or rumbling noises may also indicate that the bearings are worn. These noises are caused by excessive bearing play, broken bearing elements, and improperly seated bearings. Undeniable and annoying, bearing-related noises are an easy-to-spot sign that your bearings need replacing.
Commonly associated with bad alignment, worn bushings, and uneven tire wear, shimmying is another sign that your bearings are worn. Shimmying is caused by excessive bearing play and is usually noticeable when the vehicle is in drive. When the wheel hub assembly is rotating at faster speeds and the oscillation is greater, the shimmying gets worse. The vehicle may also drift or pull to the side of the wheel with the worn bearing because its wheel is no longer in sync with the rest of the wheels.
5. Swaying when braking
For effective braking to occur, the bearings, rotors, and brake calipers must be on the same plane. If any of these parts are misaligned, the vehicle may swerve uncontrollably during the braking process. Brakes are designed to operate simultaneously to keep the vehicle stable as it reduces speed. If one of the wheels has a bad wheel bearing, the brakes on that wheel will not function properly, as the rotor (together with the hub) is loose.
6. Malfunctioning ABS system
Damaged bearings can cause the wheel speed sensor to go out of alignment. The anti-lock braking system (ABS) relies on the sensor’s wheel speed input to prevent the wheels from locking during braking. If the sensor is misaligned, it may send false info to the computer, causing the ABS system to malfunction.
7. Unusual brake pad and rotor wear
Although not readily apparent, unusual brake pad and rotor wear is a sign of worn bearings. The wheel bearing keeps the brake rotor within and parallel to the gap between the brake pads. If the bearings are worn, the rotor may wobble within the gap, causing uneven wear on the brake pads and on the rotor’s contact surface.
What causes bearings to fail?
Wheel bearings are made of hardened steel. Advances in metallurgy enable them to withstand tremendous amounts of punishment. Bearings are designed this way to be able to handle the full weight of the vehicle, absorb forces, and sustained use. Although durable, bearings inevitably wear down over time.
The rate of bearing wear varies and depends on driving conditions and driving habits. Driving on paved roads places little stress on the wheel bearing. The opposite is true for driving on rough terrain. Driving habits affect the lifespan of bearings.
Aside from ordinary wear and tear, wheel bearing damage can be attributed to broken seals, improper alignment, and impact forces.
1. Broken seals
Broken seals are the most common cause of bearing failure. Modern sealed bearings have rubber or plastic seals that can be torn or broken. The purpose of the seal is to keep the lubricant inside the bearing assembly and keep its insides free from contamination. Due to their location, bearing seals are susceptible to damage from intense vibrations and shocks.
Bearings depend on lubrication to effectively reduce friction and heat. If the seals are broken, the grease inside the bearings may leak out, depriving the balls or rollers of much-needed lubrication. Broken seals may also allow debris and moisture to enter the bearing assembly. Dirt and moisture may contaminate the grease inside, reducing its ability to lubricate and cool the rolling elements.
Apart from broken seals, corrosion can also be caused by external factors such as condensation and humidity. Although not directly exposed to the elements, the location of the wheel bearings makes them prone to corrosion-causing moisture from the road. External corrosion on the bearing will accelerate wear, eventually leading to broken seals.
3. Impact forces
Another cause of bearing wear is excessive impact forces. Driving over potholes at high speed and driving in very rough terrain are great examples. The amount of shock transmitted from the tires to the bearings is tremendous, as they can’t avail of the damping effects of the suspension system. Impact forces can break the seals, warp the bearing cage, and deform or score the bearing races.
4. Faulty installation
Improper installation can lead to bearing failure. The bearing must be seated firmly in the hub assembly with its axis of rotation straight and true. A bearing press should be used, as the force from inappropriate tools (like hammers) may damage the bearings during installation.
Improper seating is also likely to create a play in the bearing or wheel hub assembly and may cause the wheel to wobble. If not repaired, the oscillation and vibration caused by play will almost certainly damage the bearing over time.
5. Improper alignment
The purpose of alignment is to ensure that the vehicle travels straight and true. Excessive toe and camber angles place additional load on the bearings at angles they are not designed to withstand. Proper wheel alignment ensures that there is an even distribution of load on the wheel bearings, tires, and suspension. Improper alignment can accelerate tire wear since the contact patches of the tires are uneven.
6. Poor bearing quality
Wheel bearings must be durable in order to withstand the extreme forces to which they’re subjected. Unfortunately, some manufacturers skimp on materials and processes while manufacturing their bearings. Bearings made from low-quality materials are prone to failure and wear.
How to diagnose bad wheel bearings?
The easiest way to diagnose a bad bearing is to check the wheels for play and unusual sounds. Jack up the vehicle and wiggle the suspect wheel assembly from side to side. If there’s some play, there is a good chance the bearing is worn. Unusual sounds, like grinding, may also indicate bearing wear, even in the absence of play.
How are wheel bearings replaced?
There are two conflicting schools of thought on the wheel bearing replacement. Some suggest that you only replace the bad bearing, while others recommend that you replace them in pairs. In our opinion, the latter is logical. Since the wheel bearings are installed at the same time, there is a solid chance that the other bearing is also less-than-perfect.
Wheel bearing replacement is a labor-intensive job that involves taking apart the wheel hub assembly. First, the wheels are removed from the hub. The brake caliper, caliper mount, and rotor are removed to expose the hub assembly. For front wheel bearings, the hub assembly is removed from the strut, control arms, and tie rod. The hub is then removed from the axle.
In hub assemblies with press-on bearings, the old bearing is pressed out of the hub assembly. The bearing seat is cleaned, and a new bearing is pressed into place. Everything is reinstalled by carrying out the steps in reverse order.
Newer vehicles come with non-serviceable hub assemblies. In this configuration, you need to replace the entire assembly, as the bearings are not designed to be pressed out of the hub.
How much does it cost to have the bearings replaced?
The total cost to wheel bearing replacement depends on three factors: parts cost, labor cost, and miscellaneous fees. On average, front-wheel bearing replacement costs around $600 in total. Parts may cost anywhere between $200 and $300 (for a pair of hub assemblies). Labor typically runs around $250 to $350.
The total cost also depends on whether you need to change only one pair of bearings or if you need to replace all the wheel bearings of the vehicle. Naturally, the cost of having all your bearings replaced is basically double that of just a front or rear service.
Another factor to consider is where you’re taking the car for repairs. Taking your car to the dealership can easily cost twice as much. A dealership is a great option if money isn’t an issue. You can sleep well, knowing that your vehicle is in the hands of competent dealership mechanics.
If your pockets aren’t so deep, then consider taking your car to an independent mechanic. They charge less than the dealership and can swap the bearings without a hitch. Finding the right mechanic can be a bit tricky since some may skimp on parts or procedures. Ask around or check out reviews online.
A final option – the DIY route can save you a lot of money and could be a great learning experience. It’s generally not advised to change the bearings yourself unless you’re inclined to get your hands dirty and don’t mind a bit of hard work. Keep a mechanic on standby, just in case.
Wheel bearings play a vital role in vehicle operation and safety. When they’re damaged or worn, it’s imperative they’re replaced as soon as possible. Although replacing the bearings costs money, the peace of mind is well worth the investment.