Determining if the tire should retire

Sept. 25, 2020
In 2017, there was more than 730 traffic-related fatalities associated with tire failures.

Of the wear items found on vehicles, I could think of nothing more crucial to the safety and well-being of everyone on the road than a vehicle’s tires. Carrying a vehicle down the highways of the world at more than 65 mph with thousands of pounds upon them and navigating and cornering under temperature ranges far below freezing and well above 120 degrees F, the tire has to endure a lot of punishment. And if properly maintained, can do so sufficiently for tens of thousands of miles. But proper tire maintenance and thorough inspection are equally as crucial to ensuring the safety of the tire. Learning how to properly evaluate a damaged tire for potential repair is taken for granted all too often and could be the difference between life and death. I’d like to clear up any misconceptions.

The tech’s task at hand

According to the National Highway Traffic Safety Administration (NHTSA), in 2017 alone, 3.2 trillion miles were driven in the United States. Each one of those miles was driven atop a set of tires. I know that is a silly statement to make, but think of the potential danger each time a set of tires carries that vehicle (more importantly, its passengers) down the crowded streets and highways. In 2017, there was more than 730 traffic-related fatalities associated with tire failures. This information is indicated by the Fatality Analysis Reporting System (FARS), a nationwide census that supplies the NHTSA with data. There is a lot at stake and we as technicians are offering our input as to the safety and reliability of the tires. We are the ones  who determine if they are up to the task. We had better know what we are doing or someone could get hurt. A tire is only as sound as the inspection process used to evaluate its condition.

Figure 1

One of the most important aspects of an inspection is to verify and maintain the proper pressure for the tire (this may be found on the tire placard, or in an owner’s manual). The pressure indicated on the tire itself is an indication of maximum allowable pressure. This is not necessarily what the vehicle manufacturer recommends. Always follow the recommended specifications for the vehicle. Although the tire pressure monitoring system (TPMS) had been implemented more than 10 years ago, they typically don’t exhibit a warning unless a tire pressure is significantly out of range. To operate a vehicle with a significantly out-of-range tire pressure can lead to blow-outs (Figure 1). A tire blowout is a rapid loss of tire air pressure that can cause your vehicle to lose control. Although it’s not always possible to prevent blowouts, maintaining proper tire pressure can certainly help you avoid them. Pressure not only affects the safety and longevity of the tire, but also has a large impact on fuel economy. In fact, instructing a vehicle owner to have the tire pressure maintained monthly (including the spare tire) can extend the life of the tire upwards of 4,700 miles.

Figure 2

The specifications for tire pressure are recommended for “cold.” This means the tire should have been stationary for at least three hours. To get an accurate tire pressure reading, you must measure tire pressure when the tires are cold or compensate for the extra pressure in warm tires. A helpful tip comes from an example involving a Toyota. Displayed is a capture of the Toyota TechStream scan tool (Figure 2). It has a feature called Tire Pressure Utility that compensates for ambient temperature and the effect on tire pressure accuracy. The compensating factor of the utility allows the tech to inflate the tire at a pressure different then what is designated on the placard. In this example, it’s recommended that the tires be inflated to a gauge pressure of 39.6 psi. Sensor #5 is showing that a tire’s pressure is too high (in this case, it’s the spare tire). This allows for a higher setting under warmer conditions and a lower setting under cooler conditions. It just goes to demonstrate that accurate and correct tire pressure is crucial to the longevity and safety of a tire.

The next aspect to consider is the amount of safe and useable tread left to the tire’s surface. Of course, this tread provides the necessary friction, maintaining a firm grip on the road, even under not-so-ideal conditions. Without the proper amount of useable tread, the tire simply can’t maintain traction safely. The tread is not only designed to improve friction between the tire and the road surface. It has to also manage water and direct it away from the contact area in between the tire and road surfaces. This is to limit the effect of hydroplaning. Hydroplaning is an uncontrollable slide of the vehicle that occurs when friction is lost between the surface of the tire and the road it is operating on. This happens when the water between the tire and the road can’t be displaced fast enough. The tire begins to float on the surface of the water and lifts the tire from the road (Figure 3). Hydroplaning is possible whenever water accumulates to a depth of one-tenth of an inch (0.3 centimeters) or more for at least 30 feet (9.14 meters) and a vehicle moves through it at 50 miles per hour (22.35 meters per hour) or more [source: Crash Forensics]. Hydroplaning is caused by a combination of standing water on the road, car speed and under-inflated or worn-out tires.

Figure 3

 It is advised that tire tread be inspected about once monthly (ideally at the time the pressure is being checked and/or adjusted). The treadwear indicators can be found in between the tire treads and are raised sections of rubber. These tread wear indicators represent the minimum safe amount of useable tread remaining and, once in contact with the tires rolling surface, are an indication that tire replacement is necessary.

Another trick is to use a penny as a measurement indicator. Simply place the penny (Lincoln’s head upside-down) within the tire tread. If the top of his head is invisible, it’s time for new tires (Figure 4).

Figure 4

Some states in the U.S. still adhere to a motor vehicle safety inspection program. Typically, the boundaries of tire wear are a lot more stringent in these programs than what the vehicle manufacturers are stating. With that said, local mandates trump all others to legally operate the vehicle within that state’s borders and with that state’s inspection certification. In my experience, I find that most tires don’t last long enough for the tread wear indicators to serve their purpose, though. Other determining factors that limit the tire’s longevity come into play. These factors can be avoided if proper inspection and maintenance are followed diligently. We’ll cover them later.

Age is NOT a beauty

You may tend to notice this on the older vehicles that don’t have many miles accumulated. Although the paint and interior seem to be in fantastic shape, it’s the tires that are the age-revealer. Age is a very real factor when it comes to evaluating a tire’s ability to perform properly. As tires age, they are more prone to failure. Some vehicle and tire manufacturers recommend replacing tires that are six to 10 years old, regardless of treadwear. You can determine how old your tire is by looking at the sidewall for your DOT Tire Identification Number (TIN). The last four digits of the TIN indicate the week and year the tire was made. If the TIN reads 0308, it was made in the third week of 2008. Look on both sides of the tire. The TIN may not be on both sides (Figure 5).

Figure 5
Figure 6

 As tires age, the effect of heat from the sun and heat from the road (and other environmental conditions) create a breeding ground for dry rot. The rubber of the tire starts to discolor as it deteriorates and becomes rigid or brittle and begins to fracture (Figure 6). Once dry rot appears in a tire, you only have a short time to attempt to repair the damage before the tires become unsafe for driving. Minor dry rot can be addressed by a using a tire sealant, similar to ArmorAll. Tires with advanced dry rot must be replaced. Dry rot allows air to escape the tire, making it difficult or even impossible to keep the tire properly inflated. Dry rot can also cause unnatural rubber expansion while driving that breaks the tire apart. Tires with dry rot are much more likely to develop leaks, holes and blowouts. In extreme cases, the tread may separate from the rest of the tire entirely. As the name suggests, the tires will dry and crack. Below are some characteristics to keep your eyes open for:

•          Brittleness — Dry rot dries out your tires. As essential oils leech out of your tires, you may notice that they appear and feel more brittle. You may even observe small pieces of rubber breaking away from the tire.

•          Cracks on the tread — Advanced dry rot can cause small cracks on the outside edges of your tire tread. These cracks can affect your car’s handling, even if your tread still has adequate depth overall.

•          Cracks on the sidewall — Even in minor cases of tire dry rot, you may notice cracks on the sidewall of your tire. These cracks may appear in an isolated area or extend around large portions of your hubcap.

•          Faded color —  If your tire begins to look more gray than black, it may be developing dry rot. Fading may appear before or in tandem with cracking.

Inspect tires for signs of dry rot at least once a year. Inform your customers of the importance of inspecting tires in the early spring or early fall, since winter and summer conditions can contribute to the development of dry rot. Below is a list of things to avoid that you can advise your customers of, too:

•          Abrasive or corrosive chemicals, such as pool treatment chemicals, motor oil and industrial cleaning solutions

•          Excessive or direct sunlight that exposes the tires to harmful UV rays

•          Extremely low temperatures

•          High temperatures

•          Long periods of disuse

•          Ozone generated by electrical equipment

•          Underinflation, especially when the car is driven regularly

Getting to the root of the problem

Discovering that a tire (or a pair, or even a full set of tires) requires replacement is just the first step of the process. Like any other approach, a good technician should take to a problem the realization that the tire has worn out for a reason is what is important. Getting to the root cause of the wear issue is what needs to be discovered. Otherwise, we have customer dissatisfaction, and nobody wishes for that. Like any other fault that occurs within an automobile, it does so for a specific reason. So, too, does premature tire wear, whether the wear occurs due to age, lack of maintenance or some other underlying cause. It’s up to us as automotive technicians to uncover it. Learning to read the treads as well as we do our scan tool or lab scopes will help keep us efficient, our customers happy and generate some profitable supplemental work for us to perform.

As I mentioned, being able to read the tire treads to determine what an underlying cause of premature wear is will certainly serve you well. The treadwear in the following areas is an indication, if you know what to look for:

•          Wear on outside edges — Underinflated tires wear on the shoulders or outside edges. There is excessive contact with the outer edges of the tire and the road surface as the vehicle travels down the road

•          Worn center of tire — Overinflated tires wear in the center. There is excessive contact with the center of the tire and the road surface. Always use a tire air pressure gauge when inflating tires and be sure to set them to the OE recommended specification. Advise your customer to do the same. Be sure to verify the accuracy of the gauge, too!

•          Wear on one of the edges — When the tire is worn on one side, but not the other, the camber angle is likely not within specification.

•          Cupping — Resembles the surface of a rough lake. When cupping occurs, it usually leads to poor shock/strut performance. It can also be caused by improperly balanced tires. Both conditions can allow the tire to “hop.” Jounce the vehicle and look for excessive oscillation.

•          Feathering — Looks like the end of a bird’s wing across the tread of the tire. Could be an indication of worn tie rod ends. The wear is typically caused by the tire excessively toeing in/out as the vehicle is driven down the road.

All of the above are just some examples of what can be learned by reading the tire tread wear. These are all visual indicators that can lead to faults found through physical inspection and wheel alignment. Carrying out this process can save you a lot of grief and your customers a lot of money in the long run.

Repairing a serviceable tire

For a tire to be labeled as serviceable, it must be able to fulfill its function adequately. Although a tire can be worn, it still may be serviceable. We will find ourselves as technicians faced with a punctured, yet serviceable tire. When the tire has been deemed safe for repair, only then should we proceed to do so.

Figure 7

For starters, I’ve seen many tires arrive at the shop damaged with multiple punctures. This usually occurs after a drive near the scene of a home having its roof replaced. If multiple punctures are present, those punctures should be no closer than 16” apart. Otherwise, the structural integrity of the tire is compromised and the tire should be replaced. If the tire has sustained serious damage in a crash (such as big cuts or treads separation), it should be replaced, not repaired (Figure 7). The maximum repairable injury size for passenger and light truck tires through load range E is 1/4 inch or 6mm in diameter. If the puncture in your tire is larger than the allowable repair size, the tire must be taken out of service.

Figure 8

If the situation arises when a tire is to be repaired, it cannot have a puncture in the area closest to the edge of the tread (Figure 8). A tire plug does not offer a permanent seal and neither does a patch. I’ve been in many shops and a common practice is to eliminate the use of patches or plugs and to only use a patch/plug combination. This offers the best of both options simultaneously, and also serves as redundant. Once the tire is removed from the wheel, a thorough inspection from within must be carried out. 

As a tire rotates in an underinflated condition, the tire sidewalls flex in and out as the tire meets and leaves the road’s surface. This creates heat and causes the internal surface of the tire to breakdown. This can typically be seen as handfuls of pulverized rubber (resembling pencil eraser shavings) are found throughout the inside of the tire. This is a sure sign the tire is need of replacement, as it is no longer structurally sound (Figure 9).

Figure 9

If a punctured tire is found to be in a serviceable condition and multiple punctures are neither too close to one another nor exceed the maximum safe diameter, the tire can be repaired. Although repairing a tire is not a difficult task to carry out, it must be done so properly and with great care. Learn the proper way to repair a tire by watching https://youtu.be/sx1p2bOaIU0. Follow all directions that occupy the contents of the repair solutions your facility provides. And always remember what is at stake and what is riding on those tires. Safe rather than sorry is definitely the way to travel. 

Sponsored Recommendations

Best Body Shop and the 360-Degree-Concept

Spanesi ‘360-Degree-Concept’ Enables Kansas Body Shop to Complete High-Quality Repairs

ADAS Applications: What They Are & What They Do

Learn how ADAS utilizes sensors such as radar, sonar, lidar and cameras to perceive the world around the vehicle, and either provide critical information to the driver or take...

Banking on Bigger Profits with a Heavy-Duty Truck Paint Booth

The addition of a heavy-duty paint booth for oversized trucks & vehicles can open the door to new or expanded service opportunities.

Boosting Your Shop's Bottom Line with an Extended Height Paint Booths

Discover how the investment in an extended-height paint booth is a game-changer for most collision shops with this Free Guide.