Tire pressure changes with additional heat and cold. I have a chart that basically says for every five degrees change (from a base of 65 degrees) that the air pressure changes by approx 1 1/2 pds per every five degrees of temp change. My tires say 80 lbs so at 65 deg my air pressure would be 80. At 32 deg I would air to 74 lbs. At 90 degrees I would air to 95 lbs. Go to this site for the chart:
http://www.irv2.com/forums/f84/unive...art-71922.html