Tires are expensive but they are a major weak point in RV's. They can go bad just sitting parked for months on end with sun and heat and "lack of exercise" causing cracks in the sidewalls. RV tires older than 4-5 years old by DOT date codes printed on tires, may look like new with plenty of tread depth, but if sidewalls are cracked they can come apart or blow out especially when getting a beating on a hot day. Typical tire store guys don't necessarily understand RV tires but when they tell you that sidewalls are cracked, they are not usually trying to grab your money. Keep covers over your tires to block sun damage and drive the rig once per month to keep tires in good condition.