How to service tire and wheel issues – tire grading, TPMS, NVH, and more

Wheel and tire service requirements on today’s vehicles are quite demanding. Technicians possessing the ability to address tire pressure and monitoring system (TPMS) issues and deal with noise, vibration, and harshness (NVH) are in demand. Consumers today are growing more and more accustomed to a smooth and quiet ride due to the advancements in vehicle design. Given all of the advanced technologies populating the automobile, technicians now must make sure they are adhering to all of the special precautions and service procedures. In fact, you may have run across vehicles that require additional services following a wheel alignment, such as a zero-point calibration or camera/radar aiming.

Today's tire design has evolved tremendously over the years. Tire manufacturers are working hard with OEMs to produce a tire with less rolling resistance and less NVH and continue to deliver a high level of safety.

Tire grading

The National Highway Transportation Safety Administration (NHTSA) has published a document outlining all of the uniform tire grading guidelines. (Figure 1) This document is available for download and should serve as a great reference when dealing with tires.

When installing new tires, you may have noticed colored dots placed on the sidewall of the tire. Usually, you'll see either yellow, white, or red. (Figure 2.) Some tires may have just one or a combination. But what do these dots represent? The red mark designates the lightest part of the tire, so, when you install this tire on a cast wheel, you will want to align this dot with the valve stem. When it comes to steel wheels, you'll want to look at the rim closely and find the diamond-shaped indicator with which you would align this red dot. Cast wheels are finely machined components and typically don't have the same balance offset as that found on a steel wheel. The dot is placed at the TPMS sensor because that’s the heavier section of the rim. On the other hand, steel wheels are not as refined and typically have a balance factor, hence the need for the diamond indicator.

Now, I'm sure you've seen a lot of tires that are installed on vehicles where these dots don't line up. I believe the main reason for this is because personnel servicing tires and wheels are not aware of this system. Why do you want to do this? When you follow this standard practice, you will ultimately have a far better chance at successfully balancing the entire wheel combination with the least amount of weight needed to achieve a zero-balance condition. Another good reason for following this practice is that you will be able to use this as a reference point if a customer returns after a tire repair complaining of a vibration issue. The first inspection should be to verify that none of the wheel weights had prematurely departed the wheel. Additionally, you can reference the dot alignment versus the valve stem or indicator. If you find that these have shifted, then the tire has rotated on the rim. This could be caused by a combination of things: too much lubricant used on the bead during assembly, the client recently experienced a rapid braking event, etc.

Tire rotation

Tire rotation is a service that should be performed on a regular schedule as per the vehicle manufacturer’s requirements. The reason for rotation is so that we can optimize tire wear evenly across all wheels. In most cases, tire rotation intervals typically run between 6,000 to 7,000 miles. On some vehicles, you'll find that they are not using the traditional wheel studs that are affixed to the hub assembly, but rather they use a screw-type lug nut. For these, you'll want to have a special stud tool (Figure 3) that will help with wheel assembly removal and installation. This will also help you prevent wheel contact with the brake rotor. This is especially important on vehicles equipped with carbon fiber brake rotors that can easily chip or break if a wheel were to encounter it.

Tire rotations are a great opportunity to inspect a few items, such as the brake pad thickness and suspension components. Also, take note of the surface between the rim and where it mounts to the brake rotor or hub. If you remove a wheel and observe a lot of rust corrosion or buildup on these surfaces, you'll want to take the time to properly clean and prep the surfaces before reassembly, otherwise, you will likely end up with numerous NVH violations. The date code is an often-overlooked data metric. When installing new tires, all of the date codes should be similar. Additionally, the age of the tire should be noted. Tires in excess of six years may call for replacement. Check with the vehicle manufacturer and tire manufacturer for guidance.

Tire repair

Puncture repairs can only be performed within the limits shown in Figure 4.

Proper puncture repairs include the removal of the wheel from the rim followed by an inspection of the puncture area. If the puncture is within the guidelines, then the best practice is to use the proper size patch and plug service patch with the proper tools and procedures to ensure an effective repair. (Figure 5)

Additionally, there are tires equipped with special acoustic foam insertsthat require special handling during puncture service.

Wheel alignment

A wheel alignment offers the technician the opportunity to fine-tune the operational characteristics as they relate to steering, handling, and braking performance. Additionally, vehicles equipped with advanced driver assistance systems (ADAS) may require additional services such as camera/radar aiming, steering angle resets, and more. Service information procedures should be consulted on late-model vehicles and especially for ADAS-equipped vehicles.

Tire pressure monitoring systems (TPMS)

When servicing wheels and tires with TPMS sensors, the proper service procedures usually include the replacement of the seals, gaskets, and valve cores. Be sure to reassemble using the proper torque levels which can be performed by using torque tools such as those shown in Figure 6.

Noise vibration and harshness (NVH)

You may find yourself dealing with a vibration complaint on a vehicle occurring at certain speeds and road conditions. Oftentimes these can be difficult to address. There are a few NVH measurement tools out there in the marketplace that can be used to narrow down such vibrations. Automotive Test Solutions offers their Intelligent Vibration Analyzer to help with identifying vibration sources and provides an easy-to-understand visual data map of the vehicle. (Figure 7)

Pico Technology also offers an NVH tool that can be added on their four-channel scope. (Figure 8)

The tool offers a graphical display of the vibration levels and what their sources are. The system uses a single three-axis accelerometer as opposed to the four-channel system from ATS.

Tire inspection

A thorough inspection of the tires during service should always include checking the complete tire including date codes, sizes, and tread condition. The tire in Figure 9 met up with some bad debris on the road and at first glance, it didn’t look too bad. A closer inspection revealed a sliced-out section of the tire.

Wheel and tire service has evolved, placing additional demands on the service professional. Please make sure that your shop is delivering proper services by following industry guidelines.