Under-inflated tires can be more dangerous2008 NISSAN ALTIMA COUPE

Topeka Capital-Journal, The, Sep 29, 2007

Dear Tom and Ray: Is there any way the tire pressure can increase without manually filling the tire? I was driving from Flagstaff, Ariz., to Tucson, and 30 minutes from Tucson, the tread blew off the front driver's side tire. The tire guy tested the pressure, and said someone must have put air in the tire during an oil change or something. But it had been several months since any service. Can altitude, barometric pressure, heat or speed affect the tire? It is a 1991 Honda Accord with 198,000 miles - just because I knew you would want to know. - Bryan

Tom: You are a lucky guy, Bryan. Often, when one of the belts blows off, the whole tire comes apart. Including the air. And at highway speed, that can be extremely exciting!

Ray: To answer your question, over-inflation probably had nothing to do with this. It had more to do with the age and condition of your tires.

Tom: Over-inflation 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. So unless you had your tires pumped up to 195 psi (trust us, you didn't), you didn't come anywhere near bursting the tire from too much internal pressure.

Ray: 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 isn't abused, those belts should stay attached to the rubber for the entire tread life of the tire.

Tom: But if the tire is defective (see Firestone debacle) at the end of its useful life (and since you drive a car with 198,000 miles on it, Bryan, we can't help but wonder if those tires are older than the polyester leisure suits in my brother's closet), or if the tire has been abused in some way, the top belt can separate. When it tears, it tears violently, so it is a crapshoot as to whether the next layer of rubber will tear, too, and cause a blowout.

Ray: And the most common form of abuse is under-inflating your tires. That is right, under-inflating them.

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