The recommended tire pressure for stock 18'' tires is 32psi, but does it applies to 17'' tires as well? I just bought 17'' tires for winter driving. The tire dealer said that for smaller tires, it's better to increase the tire pressure by at least 2psi per inch. So I should have 34 psi of pressure in each tire. When I check the tire pressures the next morning, it was 41psi on each tire!

 

Since there would be more surface area for the air to push out on (given the same tread width) on a 17" versus an 18", a 17" tire would need less air pressure.

I'd think, depending on conditions, anywhere between 32 and 40 psi would be safe.