Let’s set some rules about tires that may keep you out of trouble and help you recognize when a tire needs attention. If a tire deviates from its recommended pressure by 25 percent, you have to assume that there is a problem and get it checked out. For a tire required to have 35 psi that’s a loss of about 8 psi which is more than any fluctuation for temperature would cause.
Repeated need for inflation should cause the same red lights to flash, not on your dash but in your head.
Next, consider the tire conditions that merit taking a tire off the road. First for wear, we’ll go from the obvious to the subtle. Anytime cord shows on a tire it must be removed from the car immediately. Whenever extreme uneven wear is displayed on a tire it should be replaced and the front end of the car should be checked out for worn steering or suspension parts and its alignment should be rechecked. “Extreme Uneven” would mean anytime the difference in the tread depth is noticeable from one side of the tire to the other with the naked eye. When the tire is down to the wear bars, which are those raised bumps between the tread, the tire has served its useful life and will no longer provide much traction. It’s time to do your part to stimulate the rubber industry.
Now it is time to consider damaged tires which can be just as dangerous as worn tires. Any bulges in the sidewall warrant removal from the car. Gouges should be evaluated by a professional to determine if they go beyond cosmetic damage. Cracking and dry rot are a concern and should be checked by a knowledgeable person. NHTSA recommends that tires be checked after five years due to possible degradation from age. The last four digits of the DOT number on your tires indicate the week and the year of manufacture. Age becomes a serious concern for tires that don’t get enough use or are exposed to hot or coastal climates. Extreme exposure to sunlight can also accelerate the ill effects of time on your tires.
Tires that have been punctured have a set of rules that are all their own. Never have a tire repaired that hasn’t been inspected on the inside. This would eliminate all self repairs unless you are able to dismount the tire from the rim. There must be a confirmation that the condition of the tire is suitable for repair. This can only be done once the tire has been removed from the wheel.
Tires that are punctured in the sidewall should not be repaired. Punctures over a quarter inch in diameter are not repairable and punctures caused by an object passing through the tire at an angle greater than 25 degrees can’t be repaired. Two punctures close together should not be patched. An example of this would be if the two prongs of an industrial staple were to pierce a tire. Any time there is damage to the inner liner of a tire, it becomes unserviceable. This happens when a tire is driven flat.
While this is not meant to be an all inclusive list, you most likely will stay out of trouble if you follow these rules. A good practice is to be tire aware by glancing down at your tires whenever you fill your gas tank which assures a consistent periodic check.