Remember learning about shear, stretch, tension, and torque? Well, they all come into play when a car’s wheels turn.
It’s why we should never take short-cuts when it comes to changing tires and wheels.
Mistakes are easy enough to make, and I’ve seen it happen many times. When a wheel comes off a customer’s vehicle, it’s a very serious matter. Not only does it create an extremely dangerous situation on the road, but it can have dramatic repercussions for the shop that last touched those wheels.
At the very least it’s embarrassing and can cost you customers.
I’ll never forget the phone call I received from my wife after she was driving her friend’s car and the front wheel came off! I had done a service on this car for free… and I’d been in a hurry. Did I torque and clean the wheel nuts and mating surfaces correctly? I couldn’t recall because I was rushing to get everyone on their way. Something obviously went wrong!
With so much at risk when working on wheels, I thought it would be a good idea to brush up on the critical points of this important task.
If you’re lucky, the back of the mag will be clean and so will the drum or rotor surface. You can make good time when working on these cars.
But if you see a brown stain, well, that’s rust. And when it gets wet, it allows the torque to lessen. Left unattended, the wheel can get loose or even fall off. I use an air angle grinder with a Roloc cookie on it. We’ve all been warned not to use Roloc cookies for cleaning cylinder heads because they were destroying engines. But for this purpose they’re perfect, fitting in the tight areas that need cleaning, and giving the rear mounting surface a great finish.
Take a close look at the rim bead surface. There can be corrosion. Here in the Kootenays, we see a lot of it on the rim bead and around the valve stem. I use a wire cup wheel mounted to an angle grinder to clean these surfaces.
For the rotor surface, I like to use a big wire brush and a scraper. It takes a few minutes of work but you’ll get a good clean surface.
Finally, I use NeverSeize to coat the lug nuts. It will prevent galling of the threads and keep the center of the rotor or drum from corroding. If your customer gets a flat and needs to change a tire, they’ll have a fighting chance of getting the lug nuts and wheel off.
Now the most important part: torque. Apply too much torque and you break things. Apply too little and things fall apart. You need just the right amount… and for that you need the right tool. A good quality torque wrench is the only way to achieve accurate torque. Also, some WD40 spray or light machine oil will do an excellent job aiding in accurate torque.
You cannot torque a nut or bolt without oil. You simply won’t get an accurate torque reading. That’s why I suggest using NeverSeize on the lug nuts and the centre hole. Dry steel tends to gall under pressure, so you’ll get that squeaking noise when you tighten the lug nuts and you won't have an accurate torque.
If the rim beads are pitted, you can service them in several ways. Some people use RTV silicone on the rim bead surface to ensure a good seal. Personally, I use tire-mounting grease. It works great, is cheap, easy to apply with a paint brush, and squishes into all the places it needs to go. It also protects the tire and the rim from corrosion where they come into contact.
Remember, if you have a customer who races towards stop signs or has frequent panic stops, the tire could move on the rim, and this will knock it out of balance. I tell customers to go easy on the brakes for a week or so, to allow the tire and rim to settle. Then it will be time to retorque the lug nuts and make sure everything looks good.
There are many things to remember, so take your time. And if the wheels require extra cleaning it’s absolutely legitimate to charge properly for your time and materials. Your customer will likely agree it is far better to be safe rather than sorry.
You don’t want to get a phone call like I did! Sharon, I’m still sorry about that wheel off.It won’t happen again.
Ken Hart is owner of HarTech Automotive in Kaslo, B.C. He is a member of the Canadian Technician Advisory Panel.
Have something to say about this article? Say it here!
Edited comments may appear in Canadian Technician magazine.