Does your truck vibrate at highway speeds? Have you had your wheels balanced only to find that your vexing vibration still exists? Are you resigned to living with the problem? Well, to that we say, bummer. And again, bummer. And finally, you don't have to. The simple solution to your problem may be tire truing, especially if you've established that your vibes come from tires, and not from driveshafts. Tire truing is a low-tech, but highly specialized, process of shaving off the out-of-round high points of tire tread in order to create an almost perfectly round tire. Of course you can't do this at home, so don't even try. Tire truing requires a special machine with an experienced person at the controls.
The tire-truing machine operator...
The tire-truing machine operator controls the depth of the cutting blade as well as the horizontal travel of the blade via hand-operated controls. Operation is much like that of a lathe, and it requires a significant amount of experience to ensure quality results.
We recently had an opportunity to observe the simple yet effective tire-truing process at Southwest Brake and Alignment in San Antonio, Texas, and we got a before and after seat-of-the-pants demonstration of the benefits of this process. Southwest owner Ted Zrzavy has offered this service for more than 26 years, and it's extremely popular in the San Antonio area due to the state's lenient lift laws, which effectively allow large-tired rigs to be driven daily. Zrzavy says that it's not just larger-diameter tires that often need to be trued, although tires over 36 inches in diameter often exhibit the greatest need for truing.
During our visit, we also watched as Southwest trued the tires on an ambulance, and we're told the technicians there recently have trued tires for National Guard trucks, motorhomes, 18-wheelers, new Porsches, schoolbuses and telephone company repair trucks. This service is so popular that Zrzavy has assigned two full-time employees to tire-truing duties, and they're busy 10 hours a day, 5 days a week.
 This is the business end of...  This is the business end of the $5,000 Amermac machine that actually does the tire truing. It features two electric motors. One powers the drive that slowly spins the vehicle's wheel, while the other operates the blade. As the machine operates, an onboard sharpening stone sharpens the blade, and this ensures a smooth, even cut to the tread. |  Before beginning the tire-truing...  Before beginning the tire-truing process, the tire-truing machine operator uses the drive roller that slowly spins the tire to determine how much, and where, the tire is out of round. Once the operator determines the area to be trued, he slowly turns the crank that drives the blade into the tire and begins trimming. |  This 44-inch Bogger had been...  This 44-inch Bogger had been previously trued, but had to be re-trued after the tire spun on the rim. You can see the new cuts (dark area on outer lugs) that were needed to true the tire. Some tires require very little truing, while others require a significant amount of trimming. |
The tire truing process that Southwest offers is actually composed of two steps. First, the tire is trued using a specially designed $5,000 truing machine, and then the tire is spin-balanced. These steps are done with the tire and wheel on the vehicle so that the tolerances of the wheel, brake drum/rotor, spindle, bearings and so on are all factored into the truing process.
These are the chunks of rubber...
These are the chunks of rubber cut from a large-lugged mud tire in order to make it round. While it may seem almost criminal to cut into a perfectly good tire, remember that all you're doing is removing the highest area of the out-of-round tire.
Obviously, tire truing, and the subsequent on-vehicle balance job, results in the inability to rotate the tires without having them re-balanced, and if you remove a tire from the wheel for repair it must be re-installed in exactly the same position. This includes the positioning of the wheel on the lugs. This may sound like an inconvenience, but truck owners who've had their tires trued say that the benefits far outweigh the drawbacks. We rode in a truck shod with 44-inch tires that had three trued tires and one un-trued rear tire due to the tire rotating on the rim because of a combination of hard wheeling and soap being used on the rim to mount the tire (bad idea). Before truing, we could feel a vibration coming through the seat at highway speed. After truing, the vibration was completely gone, and the truck rode smoothly, even at speeds of up to 75 mph.
We found that tire truing is not for the faint of heart, because the by-product of tire truing is shavings or strips of tire, and seeing this may come as a shock if you've just forked over big bucks for a set of tires. Keep this in mind, though: The process is only removing the out-of-round portion of the tire, and for most tires, this is only a small amount. If a tire is new and significantly out of round, Southwest will recommend that you return the tire to the place of purchase for a replacement.
 One of the keys to making...  One of the keys to making sure your newly trued tires stay trued is to ensure a good bond between the tire and rim so no movement occurs. When this tire was mounted, we marked it with a chalk line and accelerated aggressively. You can see that the tire did not move on the rim. If it had moved, the truing would have been thrown out of whack. |  After the tire is trued, the...  After the tire is trued, the next step is to balance the tire on the truck. Once again, this is done so that the tolerances of the wheel, brake drum/rotor, spindle, bearings and so on are all factored into the balancing process. The truck is placed on a sensor that measures vibration, and this information is sent to the computer in the high-speed strobe light. |  With the vehicle suspended...  With the vehicle suspended on the sensor, an electric device is used to spin the wheel/tire combination at high speed. A strobe light tells the operator where and how much weight to place on the wheel. This completes the tire truing process. |
How much does it cost to true and balance a set of tires? Zrzavy says that Southwest charges about $64 a set for those tires under 38 inches in diameter, while those over 38 inches cost approximately $120 a set.
We talked with many folks who have had their trucks' tires trued, and they all say it does exactly what it's intended to do, resulting in a truck that can be driven at expressway speeds without aggravating wheel and tire vibration. For those of us who use our 4x4s as daily transportation, a service like this is just what the doctor ordered.