The Importance of Validating Torque Wrenches in Tire Shops
When you’re running a tire shop, you’re not just selling tires. You’re selling safety and security, the knowledge that when a customer drives away, they’re driving on a set of wheels that’s safe for the road. As a matter of course, the work you do on the tires themselves—patching, inflating, even re-grooving—must be done to the highest standards of quality. No less important is the fastening of the wheels to their hubs. After all, a loose lug nut can spell disaster on the highway.
Every tire job involves removing the tire from the hub, then affixing it again. The lug nuts you remove and replace must be tightened to a certain tension in order to hold properly. Too much, and they can damage the hub, warp, deform, or shear. Too little, and they can rattle loose. So, for every tire job, you must deliver a discrete, specific amount of torque to each nut—which means torque wrenches are indispensable equipment for every tire shop.
Choosing Torque Wrenches for Tire Shops
While different cars and trucks use a variety of lug nuts, since all these fasteners are designed to accomplish approximately the same task, their torque specifications fall within an approximate range. The lightest lug nuts—those of the 1989-1997 Geo Metro—require 50 foot-pounds of torque. The heaviest range up to 145 foot-pounds or higher for heavy-duty vehicles. An assortment of hand and pneumatic torque tools cover these ranges.
The best hand tools for lug nuts are click wrenches and cam-over wrenches. Both can deliver the full range of torque required with close accuracy. Some models can, by themselves, cover the entire range of torque needed. Keep in mind that click wrenches are less precise than cam-over wrenches because, while they inform their operator when torque is reached, they do not stop them from delivering more torque. Cam-over wrenches, on the other hand, use a clutch mechanism to slip when torque is reached, preventing over-torque conditions entirely.
Both continuous drive pneumatic tools and pulse tools are fast, effective ways to torque lug nuts. Continuous drive tools are softer on the nut than pulse tools but are harder on their operator. When continuous drive tools reach torque, they slip, and the operator’s body absorbs the inertia of the tool. Pulse tools, which deliver torque in a series of sharp, quick pulses, stress the fastener with their impact more than continuous tools. However, they create little to no reaction force for the operator to deal with.
Finding the Right Torque Value for Your Lug Nuts
In order to apply the right amount of torque, it’s necessary to know what that torque is. The best place to find the appropriate amount of torque for a vehicle’s lug nuts is the manufacturer’s specifications. The engineers who designed the vehicle base their specifications on large quantities of accumulated data and vehicle-specific testing. Their specifications will also take into account the assembly’s substrate material, which can affect torque values.
General torque charts do exist to supply torque values for various bolt sizes and vehicle makes. While these can serve as a guideline, as a best practice for a working tire shop, finding the manufacturer’s specifications is preferred.
Validating Torque Wrenches to Ensure Accuracy
Every part of a vehicle—from tires to lug nuts to the oil, brakes, suspension, and transmission—is subject to wear and tear on the road and must be continually serviced to maintain peak performance. The same is true for the torque tools used to service vehicles. If a torque wrench goes untested for too long, it can slide out of calibration. Then, each time it’s used, it will deliver the wrong amount of torque, potentially causing serious safety issues.
Torque wrenches should be tested and calibrated frequently based on tool usage. But how can a tire shop tell when a wrench starts to drift out of calibration? A torque wrench tester allows you to instantly verify whether a wrench is still in calibration or if it has fallen out. Ideally, tire shops should perform daily or weekly verification tests to confirm if a wrench is operating at the proper torque setting.
When coupled with a torque wrench management and maintenance program, a torque wrench tester can help you significantly cut costs. After all, this way you will not have to rely on a time-based calibration interval. Instead, you can service a wrench only when it starts displaying the incorrect torque value during in-house testing. By performing periodic validations with a torque wrench, a technician can feel confident that the tool is accurately producing the desired torque setting.
Periodic checks can be accomplished quickly with the use of a pass/fail visual feedback system. With this system, a preset target torque and tolerance are programmed into the torque wrench tester. If a torque reading falls within tolerance, then a green light will illuminate—pass. For any readings that fall out of tolerance, a red light will illuminate—fail. This way, an operator only needs to look at the lights to see whether a torque wrench is properly calibrated.
By knowing your torque specifications, choosing the right torque wrench, and maintaining tool calibration, you can be positive that each lug nut you tighten is safe to drive on. If you’re not sure how to go about any step of the process, go to the source. To find torque specifications, contact the vehicle’s manufacturer. For help finding the right torque wrench, consult an expert. For help calibrating your tools, seek out a certified service center. When you can depend on your tools, your customers can depend on your tires.