[goneballistic]

My guess is the air pressure of the larger tires is a few pounds under the O.E.M. tires. Or, perhaps front and rear rims got switched, and the pressure is supposed to be lower in the front than the rear. There is a button at the base of the dash, just to the right of the floorboard light, driver's side. With the ignition key in the on position, push it in and hold it until the low tire indicator light flashes. This should reset the set point for your tire pressure sensor input.