The official "my Yaris handles bad on the highway/with crosswinds" thread

[grampi]

Good article, but it doesn't specify exactly what is considered overinflated. If you ask around, I think you'll find most tire experts will say a tire isn't overinflated unless the max pressure listed on the tire's sidewall is exceeded. As long as you stay under that, you're fine. BTW, for what it's worth, driving on underinflated tires posses a much higher risk of a blowout than does driving on overinflated tires. Remember the Ford/Firestone debacle a few years back? Almost all of those accidents were attributed to underinflated tires.