correct tire pressure for long distance??

[sundevilMP5]

hey all

i'm going to be taking a road trip tomorrow and i was voted to drive...so just curious what the proper tire pressure for long distance is?? i know you're supposed to fill them up high but how high??

 

[Jim Frye]

Huh?????????????????

i know you're supposed to fill them up high but how high??

In all of my years of driving (35+), I've never heard of such a thing. As you drive, the tires heat up from flexing and increase the psi of the air inside. If you start out high, it will only get higher and you run the risk of overinflation. If it doesn't cause uneven wear after a long period, I would think it would alter the contact patch and affect straight line braking. I keep the P5's tires at 32 psi all the time.

 

[Skids]

Jim, you are correct, adding air to the tires does alter the contact patch. A higher tire pressure makes the contact patch smaller which very slightly adversely affects traction... which is why you hear about racers letting air out of their tires before a run, to get more traction.

But for long road trips where gas mileage is of prime concern, adding some air to the tires can be a good idea, since a smaller contact patch also means less road friction. In fact, the EPA says that making sure you have properly inflated tires is one of the best things you can do to improve the gas mileage of any car. As far as how much to add, I wouldn't go over whatever is written on your tire, but definately bump it up to whatever the maximum is listed as.