5 Things to Know Before Buying Truck Bearings

 There are many different types of bearings available today with very little information on the differences between them. Maybe you've asked yourself 'which bearing will be best for your application?' Or 'how do I choose a bearing?' This bearing selection guide will help you answer those questions.

Check now

First off, you need to know that most bearings with a rolling element fall into two broad groups:

1. Ball bearings
2. Roller bearings

Within these groups, there are sub-categories of bearings that have unique features or optimized designs to enhance performance.

In this bearing selection guide, we'll cover the four things you need to know about your application in order to choose the right type of bearing.

Find the Bearing Load & Load Capacity

Bearing loads are generally defined as the reaction force a component places on a bearing when in use.

When choosing the right bearing for your application, first you should find the bearing's load capacity. The load capacity is the amount of load a bearing can handle and is one of the most important factors when choosing a bearing.

Bearing loads can either be axial (thrust), radial or a combination.

An axial (or thrust) bearing load is when force is parallel to the axis of the shaft.

A radial bearing load is when force is perpendicular to the shaft. Then a combination bearing load is when parallel and perpendicular forces produce an angular force relative to the shaft.

To learn more about axial and radial ball bearings, contact our team of engineers!

How Ball Bearings Distribute Loads

Ball bearings are designed with spherical balls and can distribute loads over a medium-sized surface area. They tend to work better for small-to-medium-sized loads, spreading loads via a single point of contact.

Below is a quick reference for the type of bearing load and the best ball bearing for the job:

• Radial (perpendicular to the shaft) and light loads: Choose radial ball bearings (also known as deep groove ball bearings). Radial bearings are some of the most common types of bearings on the market.
• Axial (thrust) (parallel to the shaft) loads: Choose thrust ball bearings
• Combined, both radial and axial, loads: Choose an angular contact bearing. The balls contact the raceway at an angle which better supports combination loads.

Roller Bearings & Bearing Load

Roller bearings are designed with cylindrical rollers that can distribute loads over a larger surface area than ball bearings. They tend to work better for heavy load applications.

Below is a quick reference for the type of bearing load and the best roller bearing for the job:

• Radial (perpendicular to the shaft) loads: Choose standard cylindrical roller bearings
• Axial (thrust) (parallel to the shaft) loads: Choose cylindrical thrust bearings
• Combined, both radial and axial, loads: Choose a taper roller bearing

Bearing Runout & Rigidity

Bearing runout is the amount a shaft orbits from its geometric center as it rotates. Some applications, like cutting tool spindles, will only allow a small deviation to occur on its rotating components.

If you are engineering an application like this, then choose a high precision bearing because it will produce smaller system runouts due to the tight tolerances the bearing was manufactured to.

Bearing rigidity is the resistance to the force that causes the shaft to deviate from its axis and plays a key role in minimizing shaft runout. Bearing rigidity comes from the interaction of the rolling element with the raceway. The more the rolling element is pressed into the raceway, causing elastic deformation, the higher the rigidity.

Bearing rigidity is usually categorized by:

• Axial rigidity
• Radial rigidity

The higher the bearing rigidity, the more force needed to move the shaft when in use.

Let's look at how this works with precision angular contact bearings. These bearings typically come with a manufactured offset between the inner and outer raceway. When the angular contact bearings are installed, the offset is removed which causes the balls to press into the raceway without any outside application force. This is called preloading and the process increases bearing rigidity even before the bearing sees any application forces.

Bearing Lubrication

Knowing your bearing lubrication needs is important for choosing the right bearings and needs to be considered early in an application design. Improper lubrication is one of the most common causes for bearing failure.

Lubrication creates a film of oil between the rolling element and the bearing raceway that helps prevent friction and overheating.

The most common type of lubrication is grease, which consists of an oil with a thickening agent. The thickening agent keeps the oil in place, so it won't leave the bearing. As the ball (ball bearing) or roller (roller bearing) rolls over the grease, the thickening agent separates leaving just the film of oil between the rolling element and the bearing raceway. After the rolling element passes by, the oil and thickening agent join back together.

For high-speed applications, knowing the speed at which the oil and thickener can separate and rejoin is important. This is called the application or bearing n*dm value.

Before you select a grease, you need to find your applications ndm value. To do this multiply your applications RPMs by the diameter of the center of the balls in the bearing (dm). Compare your ndm value to the grease's max speed value, located on the datasheet.

If your n*dm value is higher than the grease max speed value on the datasheet, then the grease won't be able to provide sufficient lubrication and premature failure will occur.

Another lubrication option for high-speed applications are oil mist systems which mix oil with compressed air and then inject it into the bearing raceway at metered intervals. This option is more costly than grease lubrication because it requires an external mixing and metering system and filtered compressed air. However, oil mist systems allow bearings to operate at higher speeds while generating a lower amount of heat than greased bearings.

For lower speed applications an oil bath is common. An oil bath is when a portion of the bearing is submerged in oil. For bearings that will operate in extreme environments, a dry lubricant can be used instead of a petroleum-based lubricant, but the lifespan of the bearing is typically shortened due to the nature of the lubricant's film breaking down over time.

There are a couple of other factors that need to be considered when selecting a lubricant for your application, see our in-depth article 'How to Choose the Correct Ball Bearing Lubricant".

BWHY contains other products and information you need, so please check it out.

Wheel Bearing Quick Facts

• Your wheel bearing might be bad if you hear unusual sounds like humming, squeaking, clicking, and more. Also, if your car wobbles or pulls to one side, you will want to get it checked. 
• Wheel bearings are part of a car's suspension system and allow a car's wheels to turn with minimum friction. 
• Bigger, wider tires can strain wheel bearings, causing accelerated wear and tear. 
• If you hit a pothole, or road salt or sand gets past the seal and touches the wheel bearings, it could lead to premature failure and become a safety issue.

Imagine driving on the freeway when the left front tire and wheel suddenly break off, sending your out-of-control vehicle skidding across several lanes of 65 mph traffic. This is not an exaggeration. This is reality, and can happen if you fail to notice the signs the wheel bearings are deteriorating and need immediate repairs. Your wheel bearing might be bad if you hear unusual sounds like humming, squeaking, or clicking. Some experts say a bad wheel bearing can sound like a bird chirping. Also, if your car wobbles or pulls to one side, you will want to get it checked.

In this story, we'll tell you quick facts to know, such as what causes a bad wheel bearing, how long you can drive on one, and the estimated replacement cost of a wheel bearing as you maintain your vehicle.

• What Are Wheel Bearings?
• Bad Wheel Bearing: Signs and Symptoms It's Time to Replace
• What Happens If You Drive on Bad Wheel Bearings?
• How Long Do Wheel Bearings Last?
• Custom Wheel and Tire Caution
• How Much Does It Cost to Replace a Wheel Bearing?

What Are Wheel Bearings?

Wheel bearings connect a car's wheels to the axles. They allow wheels to turn with minimal friction. Though wheel bearings are low-maintenance parts, they are important safety components of a vehicle's braking, steering, and suspension systems. The one-piece hub assembly, between the drive axle and the brake disc or drums, incorporates the hub, wheel bearings, ABS (anti-lock braking system) wheel speed sensor, and mounting flange.

The bearings are tightly packed in a grease-filled, waterproof, sealed metal ring. This housing, called a race, is located inside the hub, and each wheel has one. Wheel bearings have a Herculean responsibility: They are engineered to support the vehicle's entire weight.

Most vehicles today use sealed hub bearing assemblies that contain roller bearings. While we don't address these, older cars used tapered roller bearings, which required servicing and preload adjusting to ensure the right amount of end play or axial clearance.

Bad Wheel Bearing: Signs and Symptoms It's Time to Replace

Your vehicle will signal that it's time to replace a failed wheel bearing. For example, if you hear unusual sounds like humming or clicking, then your bearing might be bad. Watch out and listen for these signs and symptoms:

1. Humming Noise

The most easily identifiable and common symptom of bad wheel bearings is audible. But it can be confusing. For example, the source of a humming noise can be linked to other issues, such as tires and the CV joint.

2. Squealing, Growling

The typical sounds of worn-out wheel bearings are squealing and/or growling. The sound intensifies as vehicle speed increases. Try to pinpoint the location of the noise because it will identify the location of the worn-out bearings.

3. Clicking Sound

If you hear a clicking sound that increases in frequency as the vehicle accelerates, there could be a problem with the wheel hub assembly.

4. Wheel Wobble

Technicians can check for wheel wobble by putting the vehicle on a lift and manually checking for wheel movement. Typically, it would be impossible to shake the wheel and tire. However, if it moves, the hub assembly needs immediate attention. The tire and wheel can literally come off the vehicle at any time, at any speed, if you don't repair your vehicle.

5. ABS Failure

The anti-lock warning light may illuminate if the ring, tire, and wheel wobble, the wheel's speed sensor is no longer operating properly, and the ABS may operate sporadically or not at all. See a professional for repair.

6. Uneven Tire Wear

If one tire wears out faster than the others, it could be a sign that the wheel bearings are worn. However, it also could be a sign the tire is improperly inflated (too much air pressure or not enough), the tires are improperly aligned, or the vehicle has damaged or worn suspension components.

7. Vehicle Pulls to One Side

Worn bearings may cause a vehicle to pull to the left or right when brakes are applied. The direction the vehicle pulls signals where the worn bearings are located, on the left or right side of the vehicle. However, this can also signal brake rotor or brake caliper problems.

8. Steering Wheel Vibration

Bad wheel bearings can cause the steering wheel to vibrate. The intensity increases as the vehicle speed increases and the vehicle turns to the left or right. However, the vibration could be linked to an out-of-round tire (there could be a flat spot on the tire) or a tire that is no longer balanced. Another cause is damaged or worn suspension components.

9. Steering Feels Loose

If there is excessive play in the steering, meaning the steering seems less responsive or less precise than normal, worn bearings could be causing the problem. Also, this could be a sign the vehicle needs a wheel alignment. If you have any of the signs listed above, visit a dealer service or auto repair shop.

What Happens if You Drive on Bad Wheel Bearings?

Driving with bad wheel bearings impacts the safety of a vehicle, and it could cause a serious car accident. We do not advise driving on them when they fail and recommend getting them checked out as soon as possible. Bad wheel bearings can damage things like your hub, the vehicle's constant velocity joint (CV joint), or the automatic transmission.

'The good news is most of the time, a vehicle will let you know way before a failure ever happens,' said Gary Hardesty, Kelley Blue Book's in-house service and maintenance expert and an A.S.E. certified master technician. 'The key is to listen to your car. Most times, a failing wheel bearing will exhibit a growling type of noise that changes with vehicle speed. The faster the car (goes), the faster the frequency of the growl.'

Hardesty cautions that if you think something is wrong, don't wait to get it diagnosed: 'The longer you wait, the more it will cost as other components may be damaged by a wheel bearing.'

Use Kelley Blue Book to find a repair shop to fix your wheel bearings.

How Long Do Wheel Bearings Last?

Wheel bearings are theoretically engineered to last the life of the vehicle. There is no maintenance schedule for replacing wheel bearings, and there is no constant source of lubrication. However, they can be damaged, leading to failure.

What Can Damage a Wheel Bearing?

1. Potholes, tall curbs (curb bumping), and speed bumps taken at brisk speeds can damage wheel bearings, making them especially vulnerable.
2. If water, mud, road salt, or sand gets past the seal and touches the bearings, it will contaminate the grease, causing the bearings to wear down, eventually leading to failure prematurely.
3. Ignoring worn-out wheel bearings can damage the vehicle's constant velocity joint (CV joint) or automatic transmission. The outer CV joint attaches the driveshaft to the wheels, and the inner CV joint connects to the transmission.

It's important to find a reputable service technician for advice to determine what next you need to do.

Custom Wheel and Tire Caution

Another thing: If you are planning to customize your vehicle with special tires or rims, be careful what you do.

The original equipment bearings on your vehicle are engineered for specific loads. Those bigger and wider tires look cool, as do tires with lower tread walls. But they place higher loads on the wheel bearings, possibly resulting in accelerated wear. That could present a safety issue if your wheel bearings fail.

It's best to stick with an automaker's specifications regarding replacements.

RELATED: Do My Tires Need to Be Replaced?

How Much Does It Cost to Replace a Wheel Bearing?

The cost to replace one front-wheel hub assembly varies widely. Among the variables are the vehicle brand and model, the garage's labor rate, and the cost of parts. The average out-the-door wheel bearing replacement cost without taxes is about $350 per wheel.

However, luxury cars are more expensive to repair. Do note that if bearings go bad at one wheel, replacing the bearings at the other wheel on the same axle is unnecessary. Don't let someone talk you into work that is not needed. Get the price estimate for wheel bearing replacement for your make and model of car.

Editor's Note: This article has been updated for accuracy since it was originally published. Rick Kranz contributed to this report. 

Contact us to discuss your requirements of Truck Bearings. Our experienced sales team can help you identify the options that best suit your needs.