tire pressure

Tennisshoes is correct. It's normal, my Corvette does this also. Usually about 4 psi according to the information display on my dash. The heat that the tires create during driving will warm the air inside them thus increasing the pressure. The pressure goes back down when the tires cool. When checking air pressure in a tire it is always best to do it when the tire is cold (as in not driven for a few hours),

On a Class A motorhome - it can easily be a 10 psi jump at highway speeds. On a car - 4-5 psi jump is normal. May be more in summer and less in winter.