Tire and Wheel Balance: A Lost Art?
Tire and wheel balance is something most of us don’t think about, until it causes a vibration or shaking in the coach that gets your attention. The problem is, a lot of shops just put your wheels and tires on a machine, spin them up, then bolt them onto your coach without knowing if the assembly is going to be smooth on the vehicle.
Tire/wheel vibration can be caused by two things: an out of balance condition, and/or an out of round condition. If we suspect that the tire is out of balance, we put it in our tire balance machine and check them out. It’s important to understand that not all tire machines are created equal, and not all tire technicians do things the same way. Variations in the way the wheel is chucked up in the machine versus the way it mounts on the coach can cause inaccurate readings; in other words, just because the balance machine says it’s balanced, doesn’t mean it will be on the coach. We’ve tried several tire balancing machines, and they’re not all accurate.
Back in the old days, the best way to determine tire balance was by spinning them up to highway speeds on the vehicle using another machine we have. We now have a tire balancing machine that has proven itself to be accurate, but when it doubt, we can still spin the tire/wheel assembly up on the vehicle as fast as 70-90 mph depending on the size of the assembly. This spinning machine is still very valuable to us when we are trying to diagnose unique problems. For example, we had a customer come in a while back whose coach was vibrating so badly, his refrigerator stopped working. He had the tires balanced more than once at another shop. It was only until we spun the assembly up while mounted on the coach that we found out the brake drums were out of balance. In that case, we balanced the wheels right on the coach with our strobe light balancer to offset the drum imbalance. That’s the way we always used to do it, but it is very time consuming-sometimes 45 minutes to balance one tire on a large vehicle.
Out of round tires can cause major problems, too. How do you tell the difference between out of balance and out of round vibrations? Generally speaking, with out of balance tires, the faster you go, the worse it shakes. With out of round tires, it will usually shake worse at a certain speed, and then you can eventually drive through it…but it could be a very high speed before it goes away. Sometimes, you can actually see if the rear tires are out of round by lifting the rear axle of the vehicle, putting the transmission in gear at idle, and watch them turn from behind. For less obvious cases, we’ll use a dial indicator to determine the run-out of a tire, and see if it is within specs for the given tire and tire diameter. Very seldom are tires perfectly round, so you have to know the specs of the tire you’re working on.
If the tire wasn’t mounted properly last time, it may not be properly seated on the bead, which will cause the tire to be out of round. This is an important thing to take into consideration before having the tires “trued”(where a special lathe is used to take the high spots off of a tire) to make them round again; if the tire is not properly seated, and you have it “trued”, you’ll end up ruining the tire. Sometimes, it may be necessary to mount and dismount the tire several times to make sure.
In other cases, the problem is caused by bad wheels; if the wheel isn’t round, it’s going to affect the tire and how it works. An alloy wheel like an Alcoa is more concentric than a stamped steel wheel. You’ll notice that more expensive cars always have alloy wheels, and this is not just for looks. It’s a rounder wheel, so there is less problems with out of round conditions, and less road harshness. Some people have had success with “automatic” tire balancers, such as the products offered by companies like Balance Masters, but we still believe that you need to have a round tire and wheel balanced properly in the first place. That means mounted up properly, with a round tire and a round wheel. If the wheel or tire is out of round, you’re just trying to compensate for it with an automatic balancing system.
I would like to end this post by paying tribute to an industry icon and friend to us all, Gaylord Maxwell, who passed away over the weekend. Gaylord had a real passion for the industry, and we have a great deal of respect for him and all of the things he did for RVers. Over the years, I have done tons of seminars at different events, but I have never seen anything like the education and training that was available at Life On Wheels conferences. Gaylord truly cared about educating RVers about so many different aspects of life on the road, from technical subject matter and safety to making a living while full-timing. Whatever you wanted to learn, he and his crew could teach you. We were grateful for his friendship, kindness, and to be invited to be part of his conferences. They have a great group of instructors and I truly hope they will continue Gaylord’s teachings for many years to come. Our prayers are with Gaylord’s wife, Margie, their family and friends, Peggy Waterman and all the rest of the wonderful people at Life On Wheels.