Wheel Bearing Preload And Endplay Explained

Preload vs endplay both affect wheel performance. Either one can optimize performance. However, because they are pretty much opposite settings, you can't set bearings to both preload and endplay. In fact, setting one will eliminate the other.

Renault truck bearing

Here's Why You Should Care

Wheel separation may sound like something from the Final Destination films, but it is a real thing – and a real problem for truckers. Wheel-offs is one of the most common causes of wheel accidents by big rigs that could be easily avoided if truckers would perform routine maintenance work on their wheel end systems. In this blog post, we will discuss pre-load settings vs. end play. Let's get started.

 

Why You Can't Ignore Preload And Endplay

It's good to understand preload vs endplay, but it's just as important to know how they influence trucks' operation and safety. For example, bearings with accurate preload or endplay settings promote even tire wear and extend tire life. Proper settings discourage vibrations that can affect seals and brake systems. What's more, proper preload or endplay helps keep bearings working correctly to reduce bearing failure and help prevent wheel-off events from occurring.

 

Preload

Preload settings on a bearing optimize wheel end performance by eliminating axial clearance. With this setting, pressure applied to the bearings keeps the rollers in place. This allows them to move the way they were built to move.

Truck bearing

Endplay

Loose wheel bearings can negatively affect the performance of tires and cause wheels to wobble. Therefore, it is important to take the time to adjust wheel bearings to make sure they have verifiable end play.

According to Timken, wheel bearing end play refers to the free movement of the tire and wheel assembly along the spindle axis. This action is applied to steer, drive and trailer axles using single or double nut systems on Class 6, 7 and 8 trucks and can be achieved with proper adjustment of the wheel bearings. Tapered roller bearing adjustments should always be performed based on the instructions from the same brand's manufacturers. If different brands are used, there is a possibility that the procedure for installation will be different. Technicians that risk using impact wrenches to fasten bearings risk over-or-under tightening them. Instead, it is best to use a breaker bar and socket then a torque wrench.

The Technology and Maintenance Council (TMC) Recommended Practice 618B states that a standard wheel bearing should be tightened to .001-.005 inches of end play and can be determined using a dial indicator.

 

How To Verify End Play

Technicians should perform a few essential steps to verify proper end play in manual wheel bearing adjustments: Make sure the dial indicator is attached with the magnetic base to the hub or drum to achieve an accurate reading. The dial indicator will need to be adjusted so the tip is against the end of the spindle (parallel to spindle axis). Read the end play as the total indicator movement. If TMC recommended end play is not achieved, re-adjust the bearing.

For Pre-Adjusted wheel bearings, the procedure is different; and the manufacture's recommendations should be checked prior to performing the maintenance work. It is important to note that single nut systems will be different from double nut systems (200-300 pounds of torque).

 

Final Thought

The Commercial Vehicle Safety Alliance just announced the theme of the 2022 International Roadcheck: Wheel-ends. Truckers that are not familiar with what to expect should read this blog post and start replacing wheel system parts prior to the June dates to avoid citations, lengthy lectures from inspectors and failing grades on inspections. By the way, we are a truck bearing manufacturer. If you are interested in our products, please contact us now!

5 FAQ About Wheel Hub Bearings

The more your shop knows about wheel hub bearings, the better you can serve your customers. Below, you'll find 5 common questions technicians have about wheel hub bearings.

 

1. Can Potholes Really Cause Severe Wheel Bearing Damage?

Short answer, is yes. Under normal circumstances, wheel bearings last a long time. Yet, potholes can do quite a number on bearings. Potholes can cause a small indentation in the bearing races. When that happens, the bearings get hung up in the depression in the race. That means the wheel bearing can't rotate as freely anymore. In addition, the bearing now has slightly more slop. Over time, the problem gets worse and worse.

It's important to be able to pinpoint why the wheel bearing was damaged. Potholes are one of the most common, yet overlooked, causes of wheel bearing damage. Here's a list of signs that indicate possible pothole damage to the wheel bearing:

• Clunking noise

• Rattling noise

• Shaky steering wheel

• Wobbly wheel

• Poor alignment

• Tire marks on the wheel well

• Damaged bump stops

• Wheel damage (cracks or dents)

 

2. How Can I Make Sure The Air Gap For A Wheel Speed Sensor Is Correct After Installing A Bearing?

It's important to keep the right distance (air gap) between the end of a wheel speed sensor and its ring. If the gap is too wide, the signal won't be strong or reliable. It'll be weak, erratic, or nonexistent. If the gap is too close, there may be some metal-to-metal contact.

When you install a new wheel bearing, the wheel speed sensor gap might change. When this happens, the ABS light will come on in the customer's car after they leave your shop. To prevent this from happening, check the wheel sensor gap after installing a wheel bearing. To do this:

• Attach a voltmeter to the wheel speed sensor's terminals.

• With your hand, spin the tire at a rate of about 1 revolution per second.

• Check the reading on the voltmeter. If the air gap is correct, the wheel speed sensor will generate between 50 and 77 millivolts AC. If the output is low, or if there's no output, the gap may be too wide.

 

3. Can Bad Alignment Angles Like Camber And Toe Cause Premature Failure Of A Wheel Bearing?

Yes. A bad alignment angle can cause a wheel bearing to fail. If the vehicle is out of alignment, the driver has to keep the steering wheel turned slightly to keep the car going straight. This adds stress to the wheel bearing, and ultimately causes the bearing to wear down faster.

4. How Should Surfaces On Axles And CV Joints Be Cleaned Or Polished Before A Bearing Is Replaced?

When replacing a wheel bearing, it's good practice to clean or polish the bearing surfaces on axles and CV joints. It's to help extend the life of the axles and CV joints. By cleaning those parts, you would be removing sludge, metal shavings, and any old differential oil that has been sitting there for a while.

The proper way to clean or polish those parts is to:

• Remove those parts from the vehicle.

• Cover the surfaces with brake cleaner or another degreaser.

• Wipe down the surfaces with a dry shop rag until clean.

If you find any hardened grease stuck on the axle, scrub it with a non-metallic scrubbing pad and degreaser.

 

5. What Is The Proper Inspection Method For A Seal?

You can visually inspect the wheel bearing seal. Grab a flashlight and then inspect it for:

• Leaks

• Cracks

• Twists

• Breakage

Sometimes the cracks are so fine that they are difficult to see. It takes a little patience to do a thorough inspection.

 

We are a Truck Hub Bearing supplier. Please feel free to contact us if you need them!