We all know that the wheels on the bus go-’round and ‘round, but that’s only because of properly adjusted wheel bearings. For your truck, you’ll need to know how to correctly adjust these bearings. Incorrectly adjusting them could prematurely wear out the bearings and hurt your truck’s performance, wasting your time and money.
Adjusting your bearings is a simple task once you’ve done it enough times. I’ll describe the process thoroughly later, but the short version is that you insert the bearing and washer, hand-tight the adjustment nut, torque it a little, spin the hub and fully torque the nut, back off the nut, hand-tight it again, then add the castle nut and cotter pin to lock it in position.
In this article, I’ll give you a step-by-step guide that shows you how to install and adjust your truck’s wheel bearings. I’ll also give some insight into how these bearings work and some important things to remember during the assembly.
What Is a Wheel Bearing?
Wheel bearings are used in many different industries, and you’ll find multiple different bearings across your car. They’re a way for cylindrical objects to smoothly rotate without added friction.
In the automotive world, friction is a very bad thing (except for between your tires and the road). Friction will cause parts to wear out quicker, can lead to mechanical failures, and will impede the performance of your car.
This is where the wheel bearing comes in. A bearing is made up of a few different parts, but the concept is pretty easy to understand.
Imagine you have a massive block of granite you need to move. You can push all you want, but it won’t budge. Now, imagine that block of granite is sitting on a series of logs. As you push the block, the logs will roll, causing the block to move with much less force.
This is what’s happening inside of a wheel bearing. The bearing will have an interior hub and an exterior shell that isn’t touching — these are both called races. Between them will be a series of balls or rollers. The balls should be perfectly smooth and spherical.
As the inside hub rotates, the balls will rotate, allowing the exterior hub to rotate with very little friction, and vice versa.
Without a wheel bearing, the interior shaft will rub against the housing and wear down very quickly. This will cause a lot of energy to be lost while destroying both parts in the process.
In a typical wheel bearing assembly, you’ll see two types of bearings. An inner bearing will be located on your wheel hub that is a traditional bearing. It’s easy to miss if you don’t know what to look for.
There will also be an outer bearing (which you’ll be adjusting) that has exposed rollers that can be seen from the outside. They extend past the outer race, making it even more important to lubricate and install them correctly.
Where the Wheel Bearing Is Located
In this case, I’m talking about a bearing that goes on your wheels. You might not have even known that there was a bearing here.
If you take your tire off and look at your wheel hub, you’ll see the bearing in the very center. Well, you won’t “see” it — you’ll see the nut that locks it in position.
As your axles spin, this bearing will allow your tires to spin with very little friction.
How the Adjustment Works
In the world of wheel bearings, there are two types: pre-set and standard bearings. In this case, I’m talking about a standard bearing.
By performing this adjustment, you’re fine-tuning how much clearance there is between the inner and outer races of the bearing. In other words, you’re changing how much space the interior balls have.
Wheel Bearing Adjustments are Picky
This process might seem really simple, but the wheel bearing is surprisingly picky. Too much pressure or not enough can lead to very big problems.
If the bearing is too tight, then there is too much pressure. In this case, the interior wheels or balls can get squished. This generates more friction, creates more heat, and subsequently melts away the lubricant faster.
If the bearing is way too tight, then the wheel will have difficulty turning to begin with and your tires can pay the price. This is only possible if you use a power tool or hand tool to tighten it.
If the bearing is too loose, there’s too much play. As you drive, the natural vibrations from the road will further loosen the bearing, potentially causing your wheel to fall off while you’re driving. At the same time, the bearing won’t be fully sealed, and the internal balls won’t be in the perfect location. Both of these problems will result in the wheel bearings prematurely wearing out.
Adding Lubrication to Your Bearings
In almost every case, the reason that you’ll adjust your bearings is that you just took them out to lube them.
Since the bearing is responsible for keeping your wheels turning, this is an important piece of maintenance. If there is not enough lubricant, then the balls within the bearing will start to wear down and rub against one another.
Once this starts, it’s impossible to reverse. It typically leads to you completely replacing your bearings.
Most manufacturers suggest taking your bearings out and lubing them every 30,000 miles or once every two years. As you’re driving, the lubricant within the bearing is heating up. Once it gets hot enough, it will melt off and oxidize the bearings.
Over enough time, the lubricant within your bearings will be useless. It will no longer help the balls roll evenly and smoothly. This process happens roughly every two years, hence the suggested maintenance period.
Replacing Worn Bearings
Another reason why you might need to adjust your bearings is that you’re replacing them. If you notice wear on your old bearings, you’ll need to swap them out with OEM bearings.
This might happen every 100,000 miles or so. With proper lubrication and care, your bearings might outlast the rest of your vehicle and you’ll never have to worry about it.
However, I should emphasize the importance of using OEM bearings. Aftermarket options might not be correctly packed, and the bearings could be slightly defective. If this is the case, they’ll wear out prematurely and lead to huge performance issues for your car.
It’s very difficult to detect these inconsistencies by eye. That’s why I always suggest using OEM options for parts like these. OEM bearings come with a guarantee from the manufacturer that the product is made for your car and correctly fabricated.
How to Adjust Truck Wheel Bearings
For semi-truck drivers, the guide to this wheel bearing can be followed along by looking up the RP-618 document. For other drivers, your owner’s manual most likely will not include any information about adjusting the bearings.
1. Ensure You’re Done Maintaining the Bearings
Before getting started, you should make sure your maintenance is complete on the bearings. This means correctly lubricating and repacking the bearings.
The lubrication process is pretty straightforward. If you haven’t done it yet, you’ll need to follow a three-step guide:
Remove the bearing, clean it with a rag and check for mechanical damages, then add new lubricant to it. You can add the lubricant by putting a heap of lube on your palm and using the other hand to push the bearing into the lube. Rotate the bearing and repeat the process.
It’s also a good idea to grease the spindle and the seal area of the spindle where the bearing will be re-installed shortly.
2. Your Wheel Should Be Accessible
At this point, I’m assuming that you’re hot off the heels of removing and repacking the bearings. I’m assuming that the tire is removed, and the wheel assembly is fully accessible. More specifically, the hub is removed and the bearing is on your shop table, fully re-greased.
If that’s not the case, then you should spend some time getting back to this point so that the bearings can be re-installed correctly.
3. Put the Hub Back on
When you’re ready to get started, you’ll need to put the hub back on. This is the large metallic piece of your wheel assembly that has threaded rods sticking out of one side. In the center is your inner wheel bearing which interfaces with the outer wheel bearing you just lubricated.
Realistically, the hub can only be installed in one direction, but it’s important that you don’t try to force it in the wrong way. If you do, you won’t be able to finish the rest of the assembly, but you’ll be scratching your head the whole time.
The threaded rods need to stick out away from the car (towards you as you look at them). Be careful when you handle the hub. If you drop it, you risk damaging the inner bearing or bending any of these threaded rods. Either of these scenarios is pretty devastating.
The hub gets installed with the center hole slipping over the axle’s spindle. It also needs to be pushed back enough to complete the seal. If you look at the spindle, you’ll see a black rubbery area at the base — this is the seal.
To fully engage the seal, you’ll need to push the hub back far enough.
4. Install the Outer Wheel Bearing
The outer wheel bearing is the one that you greased earlier. This gets installed by simply pushing it over the spindle, inside of the hub.
Once pushed in, your outer wheel bearing will be in contact with your inner wheel bearing, with a seal keeping the backside closed.
5. Install the Keyed Washer
There will also be a keyed washer that gets installed. You should have noticed this piece when you were disassembling everything earlier.
This washer creates a gap between the bearing and the nut that you’ll install later.
You’ll notice that the washer’s interior doesn’t make a circle — there’s a notch jutting down. This is the “key”.
This key will align with a keyed slot cut out of the spindle. The washer won’t assembly unless it’s oriented correctly, which is good news.
There’s no science behind installing the washer, just slide it over the spindle as far back as it goes.
6. Install the Adjustment Nut
Take the adjustment nut and fully thread it on by hand. It’s important that the initial installation doesn’t include any tools yet, so just use your fingers.
There’s no directionality to the nut, so don’t worry about flipping it over and only threading it a certain way.
Before moving on, double-check that the nut is tightened by hand, pushing against the keyed washer.
7. Add a Little Torque
This is the official start of adjusting your truck’s wheel bearing. It starts by adding a little bit of torque. In the past, I’d add about 100 to 150 inch-pounds of torque to the nut using a torque wrench.
For exact specifications, I would check with a service repair manual for your vehicle to apply the correct amount of torque.
This should be done without touching the hub at all. You should just be touching the torque wrench and torquing down the nut to a small figure.
8. Spin the Hub
The previous step was just a quick way to get the nut in position and ensure everything is straight before this step. In this step, you’ll actually be spinning the hub while your torque wrench is grabbing the adjustable nut.
How does it work? You hold the torque wrench in position with one hand while spinning the hub with the other.
Your owner’s manual will have a suggested torque value for these adjustment nuts. In general, it’s somewhere around 300 or 400 (higher, depending on the size of your truck).
Hold the torque wrench still while spinning the hub counterclockwise. Doing so will tighten the nut to the torque value I just mentioned. This process will add a pre-load to the bearing, setting the distance and squeezing out any extra grease from the outer bearing.
9. Back Out the Nut a Little
After doing that, you’ll need to back out the adjustment nut. How much you back it out can vary from truck to truck, and different mechanics will suggest different techniques.
Personally, I only back the nut out about a half turn. Some mechanics will entirely loosen the nut then re-tighten it, so it’s up to you.
10. Tighten the Nut Finger Tight
Regardless of how much you backed out the nut, you’ll need to now tighten it finger tight. Remember, this means just using your hands and no tools.
11. Add the Castle Lock and Cotter Pin
Now you’ll put on the castle nut. This weird-looking nut looks like the top of a castle and can have a few different keyways. You’ll want to line up one of the keyways with the key in the spindle.
Doing this should give you access to a hole to put a cotter pin through. Speaking of which, now you need to insert the cotter pin.
If the holes don’t line up, just rotate the castle lock and try again.
With the cotter pin installed, bend the two legs up and around the castle nut. Cut off the excess and never have the cotter pin outside of the envelope of the castle nut.
12. Add the Dust Cap
Finally, reinstall the dust cap. This is the metal domed piece that covers the internal assembly and keeps contaminants away from the delicate bearings.
You’ll need to tap the dust cap in place. The best method is to use a rubber mallet and tap along the outer ring of the dome. If you’re careful, you could use the back of a wrench or a hammer to achieve the same result.
The goal is for the dust cap to be fully seated so dust can’t sneak into the assembly.
13. Finish the Installation
At this point, your truck’s wheel bearings are fully set and adjusted. All you’ll need to do is finish the installation by adding your brake assembly and wheels.
As you just learned, adjusting truck wheel bearings isn’t as daunting as you might think. There’s a lot of science going on behind the scenes, but the actual assembly process is straightforward (in my opinion, at least). If this guide helped, let me know in the comments below. For more truck maintenance guides, explore the rest of my site. I also put together a list of car care products that I highly recommend, so take a look at that too.