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== over inflation almost never causes tire failure ==Bill Woehrletire engineer, and now runs a company called TFI: Tire Forensics InvestigationBill says that overinflation almost never causes tire failure. The standard tire is inflated to about 30 to 35 pounds per square inch. Under hot weather and highway conditions, the temperature of the air inside the tire rises about 50 degrees. That increases the pressure inside the tire about 5 psi. The burst pressure of a tire is about 200 psi. Bill says that the most vulnerable part of any steel-belted radial tire is where the steel belts are attached to the rubber near the edges of the tread, also called the “shoulders” of the tire. If the tire is not abused, those belts should stay attached to the rubber for the entire tread life of the tire. But if the tire is defective (see Firestone debacle) at the end of its useful life, or if the tire has been abused in some way, the top belt can separate. When it tears, it tears violently, so it’s a crapshoot as to whether the next layer of rubber will tear too and cause a blowout. And the most common form of abuse is underinflating your tires. That’s right, UNDERinflating them.Woehrle says that underinflating the tire puts additional stress on the tire’s shoulders, where the belts are attached. And if a tire is underinflated by 10 or 15 psi, the temperature at those shoulders can reach 200 degrees. So you’ve got a vulnerable part of the rubber that’s hot being stretched and pulled, and that’s a recipe for tire failure.By the way, overloading the car with say, luggage or two mothers-in-law does the same thing as underinflating the tires. It stresses the shoulders of the tires.So Bill says if you’re going to make a mistake in inflating your tires, it’s much better to overinflate them a bit than underinflate them. There are really no horrible ramifications of overinflating the tires by 10 or 15 psi, except that when you go over bumps you’ll bounce up and hit your head on the dome light.But the dangers of underinflation are catastrophic tire failure. So for all of our readers: Make sure your tires have sufficient tread and have not exceeded the manufacturer’s mileage rating. Make sure they’re less than 10 years old, even if they have low miles (because old rubber gets brittle and has a greater tendency to crack). And check your tire pressure at least once a month to make sure your tires aren’t underinflated. source: https://www.denverpost.com/2007/09/29/can-tire-pressure-rise-on-its-own/