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In 2012, the NHTSA (National Highway Traffic and Safety Administration) published data on traffic accidents showing that of traffic crashes where it was determined the vehicle was the primary cause of the accident, 35 percent of those were caused by some form of tire failure: a failure that may have been prevented by proper inspection and maintenance.
Doing a current internet search for data on tire failure and vehicle crashes brings up a lengthy list of legal firms that will help you sue everyone — from the tire manufacturer to the technicians who’ve worked on your vehicle — if you were involved in a tire failure traffic accident. That should concern you, if not outright scare you!
I can already hear the mumbling that "I've been doing this for X years; I KNOW how to inspect a tire." Or, "Since 2008, we've had TPMS; what else do we need to worry about?" I would be dishonest if I said I hadn't had those ideas as well. But then I sat through a presentation by T.J. Tennet, The Tyre Guy, a former lead engineer at Bridgestone Firestone. After listening to him, I said to myself, "We educators need to be sure we are teaching this to the new techs, to recently graduated techs, and to old-timers, like me." Up front, let me thank T.J. for being the inspiration for this article and one of my sources for the information to come.
It is not just aftermarket repair facilities that need to be concerned; dealers and fleets have the same liability when working on tires and rims. How many municipal fleets out there have a fire truck that is 10-15-or more years old with the original tires on it?
Let’s start with what we all should know about and it is tire age. I didn't know much beyond the idea that sooner or later they get too old. There is an inspection, and the results may be difficult for your customers to accept.
Part of the DOT number that is on every tire is the date of manufacture. Before the year 2000, the number was three digits, the first two indicating the week and the last one indicating the year. Since 2000, they are four digits with the first two the week and the second two the year, so take this code, 2015. Made in the twentieth week of 2015. This one: 489, the forty-eighth week of 1999 or 1989. Time to replace regardless of tread depth.
Time is of the essence
Tire experts will tell you that a tire has a six-year timespan before the environment and the degradation of materials takes its toll on it, to the point it should be replaced. This timespan has nothing to do with tire wear, and it does not even have anything to with whether the tire is even in service.
Others may say that between six and 10 years, the tire should be removed from the rim and checked internally and externally for concerns. After 10 years, they say, it should be replaced. Some of you may be raising an eyebrow, as we all know people with classic cars that have the original tires. The tires are holding air, they have tread and they ride down the road. The unanswered question on these tires is, "Are they safe?" According to the people who make the tires, they are not.
Just before COVID shut down the world, I was teaching a service floor class and was running some students through balancing tires. We had taken a set of tires off a donated vehicle that was being scrapped out due to age. It was a 2005 Nissan and no longer fit the program needs. Try as they might and with the use of a road force balancer, they could not balance a set of tires that had less than 100 miles on them, but they were 15 years old. The vehicle had spent most of its time sitting in the lot or a lab. The tires were flat-spotted, and no amount of road force balancing, nor any amount of driving would have fixed them.
Some advice to dealers: we are seeing images of brand-new vehicles stored in lots, waiting for components housing computer chips. Once these vehicles get their components and are delivered to your store, you will want to drive them as part of your pre-delivery inspection, to check for flat-spotted tires that may need replacement. It doesn't take 15 years to permanently flat-spot tires beyond repair.
Have they met their match?
Do all tires and rims match? I’m sure alignment techs do this inspection before putting the car on the rack. Do all four tires match? By “match,” I mean are they the same size, the same manufacturer, the same model, and the same tread pattern?
Not having matching tires does not mean that there is a danger of imminent tire failure. Matching tires is a safety issue due to degraded handling capability. The vehicle's suspension was designed with specific-sized matching tires and on some vehicles tread patterns. This includes expected traction capabilities to be able to handle not just dry pavement but adverse driving conditions as well. Different tread patterns may work against each other causing poor stability or loss of control during adverse driving situations.
Mismatched tires are more than just a safety issue while driving. When I was training for Ford, we told the tale of the Lincoln Town Car that would at random times engage the traction control to the point of bringing the vehicle to a stop. Upon stopping and restarting, the car would drive normally until the next event. It was at the third dealer before a tech finally noticed that there were three tires of one brand and the fourth of another on the car. All of them were the same size, P225/60R17s — but not really. Somehow it got out of the factory, made it through pre-delivery, and was delivered to the customer without anyone noticing. The mismatched tires were on the rear-drive wheels and during certain times of driving there was sufficient speed differential to engage the traction control. Replacing the odd tire fixed the problem.
While all four of the P225/60R17 tires are theoretically the same size, they are different. Construction methods and materials will give the tires different rolling diameters. This may cause enough speed variation to engage or disable ABS or traction control systems.
Yes, when replacing tires, you need to put all four on. Exceptions to this? There shouldn’t be but occasionally there are. Anytime you're dealing with 4-wheel drive, All Wheel Drive, or vehicles with ABS and traction control, all of them need to be replaced at one time. (There may be instances when the tires are nearly new and there is a failure that one or two might get replaced without a problem, if they are replaced with the same tires).
On vehicles that aren’t so equipped, you could put just two tires on. Make sure that they are installed on the rear of the car. Studies show that it is safer to do so. Better traction in the rear will cause understeer and the experts consider understeer to be safer to deal with than oversteer.
When replacing tires that are not OE fitment, make sure the tires are comparable, such as “green” tires for electric and alternative fuel, Euro-rated tires for certain imports, light truck tires, and trailer tires on RVs and other trailers.
If changing tires and wheels to increase load carrying capability, many of these aftermarket tires also require higher cold pressure settings. For the TPMS system to work correctly, and the speedometer as well, part of installation needs to be recalibrating the appropriate modules for the new tire pressure and, as necessary, the new tire size. You also need to install a new tire placard listing the new size and pressure over the existing one.
Understanding the limitations
With tire pressure and tire load, there is a direct relationship with load rating and tire pressure, to a point. Going past the maximum pressure rating does not increase the load capability.
Tire repair? If the puncture is in an area of the tire that has steel belts, most manufacturers allow you to dismount the tire and patch from the inside using a patch/plug. Do not use just a patch and do not use a string patch. While you have the tire off the rim, make sure you do a good inspection to look for damage that may have occurred if the tire was run flat or very low for any length of time. Tire repair may affect the speed rating of the tire, look that up and let your customers know if that is the case.
What about Special Trailer (ST trailer) tires? Pull up any RV-related forum and you find more opinions about tires than you thought possible, most of them about blowouts. Whenever I read about a tire blowout, I have questions that come to mind, long before my thinking that ST tires or a brand may be junk, which is what is often being said.
Are your trailer tires (are any of your tires) going to blow up if you go too fast? Are they going to blow up if you overload your vehicle? Are they going to blow up if you drive them underinflated? Again, the definitive answer is, "maybe." What I can say is that you have increased the likelihood of that happening and as the forums prove it does happen.
This is a tech tip for anyone thinking of checking tire pressures on a vehicle. Yes, you will need to have specialty equipment, either a scan tool with bidirectional capability or a tool like the Bartec, VXDAS, Autel, etc. You will want to have a process — "test before you touch" is one — the idea being that you use a scan tool or one of the standalone tools to ping the TPMS sensors to check their operation. There is little that is more frustrating than to try to remove a valve stem cap to check the pressure and have the stem in your hand and a tire that is now flat.
It is against federal law to disable a TPMS system. If you work on the system, it must work before you release the vehicle to the customer. If you don’t work on the TPMS, document that the system wasn’t working and that your shop did not do any repair work on the system. Get signatures! Talk to your lawyers for more specific advice.
Going above and beyond
Getting back to tires and the TPMS system, there are aftermarket replacement tires that can be safely used, that have different load ratings and pressure requirements than OEM. As long the load and speed ratings are higher than OEM fitment they can be safely used. This is also true for the rims. Tires that are of a different size or type of construction will need new rims. Rims also have load and speed ratings and need to be equal to or greater than original OE specifications and fit the new tires being installed.
Sometimes the type of tire isn’t available in the OE size. When you need to change the tire and rim size you can, by going up or down 10 percent on the profile, you change the rim diameter by one inch and maintain the same height and diameter of the tire. While it is not a perfect one-to-one change, it is close. A 255/45R20, a 255/55R19, or a 255/65R18 are for all practical purposes the same sized tire. They are close enough that you need not worry about speedometer accuracy, ABS, or traction control, as long as you replace all four at a time.
One more tire pressure and TPMS tip, for use with educating your staff and customer base. The TPMS system is designed to illuminate when pressures drop by 25 percent or more (some systems will also illuminate if pressure exceeds 25 percent of the placard). There are tire experts who will tell you that 25 percent is borderline, and if the vehicle runs with the light on for any length of time, that may cause damage to the tires. You want to recommend an internal tire inspection when your customers show up with the light on and low pressure. You want to impress on your customers that as soon as that light may be on that they air up their tires, or stop by your shop and get pressures adjusted, and perhaps a quick close look for concerns.
Safety (and liability) is key
Reduce your liability and give your customers better service.
Get a copy of the latest yearbook from The Tire and Rim Association. This book has all the specifications that you need when maintaining, repairing, replacing, or modifying the tires and rims on your customers’ vehicles. Got a customer concerned about their tow vehicle and whether their tires can handle the added load? How about how to determine what rims tires with a different profile require? This book has it.
For example: Looking at the yearbook for 285/45R22 114H tires, it shows that at 38 psi, the max load is 2,480 pounds. Max pressure is 41psi, and the load-carrying increases to 2,601 pounds. Increasing PSI above 41 will not increase load-carrying ability. It also shows that the overall load of the vehicle is a max of 1342 pounds.
Another book to get is by ATA Business Solutions and is called the “Radial Tire Conditions Analysis Guide.” Also, the “Passenger & Light Truck tire conditions manual” published by the Tire Industry Association is another excellent source to learn what causes wear patterns on a tire besides alignment angles.
Education keeps us and our customers safe, and being safe should always be our number one priority.
