RALEIGH — Since the massive Firestone recall began, people have been talking about tire pressure. What is the right pressure? How often should you check your tires? What is the best way to do it?

Many functions are automatic in modern cars, but checking tire pressure is still something drivers have to get out of the car and do themselves. That is probably why so many people do not do it.

Over a couple of months, air may slowly and silently leak out of the tire, leaving the driver at risk of a blowout.

Anthony Blackman owns a tire shop in Cary. He sees many tires that could have stayed on the road longer if drivers had their tires checked every month or used a gauge to check for themselves.

A visible sign of a pressure problem is extreme wear on the inner and outer edges of the tires.

Blackman says drivers should not rely on sight -- they should use a gauge. Also, do not go by the P.S.I. printed on the tire. Instead, drivers should look inside the door jam.

"It's very easy to find," Blackman says. "It's right there. It'll tell you what the engineers who designed that vehicle suggest that you have in there."

A few pounds of pressure make a big difference. Properly inflated tires will give drivers better mileage from their vehicles and less wear on their tires.

A lot of people decide they need to add air if they see a bulge on their tire. If it is a radial tire, that bulge is normal, but use a gauge to be certain.

For drivers who do not want to get their hands dirty, most gas stations have plastic mitts they can use to check their tires.