For many, the true tire part that gets no love are the tires. Yet, so few think about the foundation upon which those tires rest. The fact of the matter is if you haven’t done a comprehensive review of your wheel installation procedures, you may be missing a critical step in ensuring your vehicles are safely maintained and kept up.
Ask any fleet technician and he or she will tell you that wheel installation is about a lot more than simply putting them on and torqueing them down. If you operate with that belief in mind, you’ll have more than one-wheel separation incident in your future. Still, this doesn’t mean proper wheel installation is rocket science.
From a Technician’s Perspective
When a technician goes about changing a wheel, they often refer to the tightening process as torqueing the nut, yet there is far more to it than that. What is more important is the amount of force being clamped down. Clamping force is happens because of the amount of tension placed on the stud. When the proper amount of force is applied, tension results from the ensuing interaction between the amount of torque applied and level of friction.
Fleet technicians must consider the wheel’s limitations. If a combination requires 40,000 pounds of clamping force, then 400 lb-ft of torque must be applied. So, where is the problem? The previous scenario takes for granted that you are completing the work under optimal conditions.
Is the assembly you are working with brand new? Have you completed all the installation steps required and is the hardware in good condition? If these variables are different, you may find yourself in a difficult situation. Now the question is, where does one start to ensure the job is done right?
Take A Closer Look at the Hardware
How should you handle the hardware during a wheel change? Take your first hard look at the hardware you’re working with. Is the wheel cracked or broken? Are there any imperfections, blemishes, or damages to the stud holes that may interfere with getting the job done right?
It is important to never overlook the condition of your vehicle’s stud holes. When a stud hole is overly elongated, that could be an indication that the wheel was loose on the hub in some fashion, at some point in time. Elongated stud holes generally point to a wheel that should be put out of service. The last thing you want to do is risk the safety of your truck driver – or those around him or her on the road – on the hopes that a wheel may or may not be serviceable.
After you have assessed that your stud holes are the proper shape, it is important to check for corrosion. Are the threads in good condition? Look specifically at damage or corrosion. Ensure there are no paint contaminants and that the length and diameters are all correct. There is a lot of careful attention that must go into ensuring a wheel is not compromised.
Ask the following:
- Do the wheel threads match the nuts?
- Are you working with English or metric sizing?
- Will you need to replace adjacent studs should you need to replace one?
Some say that if you have two or more damaged studs, it is safest to replace all 10 studs with new hardware that matches the size and placement requirements. Other motor carriers operate with the belief that good quality studs will last a long time provided there are no catastrophic failures.
Remember, a stud stretches like a spring. Therefore, the amount of torque you apply is so critical. Since torque and clamp load are so interrelated, you cannot make a mistake in the amount of pressure you apply and not expect there to be a countervailing problem. When you under-torque, you risk having loose wheels and when you over-torque you risk stretching your studs.
Taking a Closer Look at Wheel Surface
When a fleet technician encounters loss of clamping force when they are changing a wheel, it is usually because there are other installation problems. Had the hub and wheel mount been properly cleaned prior to installation? It is important to make sure that surfaces encountering each other are not contaminated with rust, dirt, or any other substance that could interfere with the amount of clamping force being applied.
While these materials will eventually wash away for fall off, they can create problems during a wheel replacement. Steel wheels are especially vulnerable to corrosion. Old steep and paint can flake away over time and use. If these substances are found, what is a technician to do?
First, it is critical that a fleet technician getting ready to change a wheel have a wire brush handy. Wire brushes are vital tools for removing loose material or excess paint from steel wheels. Since paint compresses under a heavy load clamp, over time the loose material can compound on the wheel’s surface. Wheel loss could result when excess material is not cleaned from the wheel’s surface.
When wheels go through a refinishing, a paintbrush should never be used. Wheel painting is only successful when there is an even thickness to the coating. The coating should not be any more than three to three-point-five millimeters thick. This rule should be especially followed where the mounting surfaces and bolt holes are concerned. When a wheel is excessively coated with paint, you wind up with a loss of clamping force, which itself can compromise the wheel.
Refinishing wheels can save your fleet some money, but it can also cost a lost more if it is not completed properly. When a wheel goes through the stripping process, it needs to be carefully controlled to ensure the original wheel or paint surface is not left over. If your wheel is deeply pitted, it may be wise to consider retiring it and moving on, otherwise you may be putting the safe operation of that vehicle at stake.
Paint should always be applied to a wheel’s surface as evenly as possible. Although wheel refinishing spray can be used, you might not end up with the most even application, which can cause problems down the road. Has your shop supervisor considered a paint thickness audit? It is of vital importance that wheels receive a consistent, even coating to prevent mounting surface problems.
Taking Proper Re-Installation Precautions
Have you inspected all your wheel studs, replaced any that may show damage and/or removed rust or taken a wire brush to them? With that done, you now must consider the proper procedures to hoist, place, and install the wheel with minimal headache.
Are you utilizing two-piece flange nuts? Make sure you are not reusing nuts that have seized up or given you difficulty in the past. Finding nuts that are in good shape should be of minimal cost compared to what might happen if you reuse bad nuts and wind up in a dangerous situation with an accident at risk.
If you do find you need to replace nuts, studs, or any other parts, make sure you replace them with manufacturer-quality parts that have the same grades and ratings. The last thing you want to do is buy a new part in the hopes you avoid a catastrophic problem only to cause a catastrophic problem because you bought the wrong parts!
When you are utilizing a part that isn’t up to the job, you risk a failure down the line that could lead to an unnecessary road accident. It is important to remember that there are no regulations or industry oversight regarding equipment that is either deficient or too damaged to function. Of course, if an inspector finds problems with your wheels that could present a safety danger, you may wind up on the wrong end of a violation.
The Final Word
If you are working with nuts that are in good condition, try using a couple drops of motor oil on the studs and threads to ensure they are clean. Another one or two drops between the washer and the nut couldn’t hurt. The point is reducing friction, which provides a better environment for strong clamping force when the wheel is torqued.
If there is one adage that a fleet technician worth their salt lives by, it is that tighter is not necessarily always better. Do not use more than the appropriate amount of clamping force, otherwise you risk facing unwanted consequences.
If there is one note of caution in this entire post, it is that you should never underestimate or provide a lesser level of care to your wheels. Sure, you keep a close eye on the state of your tires and the performance of your engine and other under-the-hood parts, but the wheels provide the basis for everything else upon the truck runs.
Ensure your fleet technicians are properly evaluating, replacing, and repairing wheels on your vital assets and they will last that much longer out there on the open road.