Tires on RV are not the same as on your car or light truck. They do not have the same UV protection. As a general rule, tires over 7 years old should be replaced. Watch when you buy tires and check the date of manufacture. It will be a four digit code on the sidewall near the DOT symbol. The first two digits are the week of the year and the last two digits are the year that the tire was made. So a 5109 would be the 51st week of 2009. Have you checked your tires?