I have Bridgestone Turanza 215-55 x 16 H rated tires on stock 5-spoke wheels on my '97 SE. I'm wondering how a change in size is affecting the pressure of the tires contact patch on the road. I live in Minnesota where rain and snow is common. I'm thinking of staying with the stock size to get better traction. Any comments?

 

If you disregard sidewall stiffness, the size of the contact patch is strictly a function of air pressure. Think about it, the only thing holding the car off of the ground is air pressure.

What changes with wider tires (at the same psi) is the shape of the contact patch, not the area.

I know that a narrow tire will give you better staight line trackability and that a wide tire will give you better turning responsiveness, but I have no idea which will be better in the snow. We don't see much of that stuff in New Orleans.

 

I was thinking a lower wider tire would have more rubber on the road (more area) and so less psi (on the road I mean, not tire air pressure).

 

No, lower tire pressure will make a larger contact patch, not a wider tire. You are correct that a larger contact patch will have a lower psi on the pavement because the total "p" is the weight of the car.