Howard Black

During vacation, I have a tire blowout and need to use the spare tire. Well, the spare is a smaller wheel and tire than on the new truck. Finding the correct tire anytime quick is shear luck. Original wheel is 22" and the spare is 20". Height is 1"1/2 different. Does driving the truck 500 miles to get home harm the vehicle? If so, why does GM put harmful combinations on the vehicle? Thank you for your help. HAB