Many tires are replaced because of old age over being worn out. One of the worst things for a tire is not being doing its job (an RV in storage). When tires are used, they release compound lubricants that can help extend tire life and they don’t develop flat spots. A tire that is not in use can degrade from ultraviolet (UV) exposure and when left on the ground can soak up water which can also accelerate tire degradation.
The life expectancy of a trailer tire varies from manufacturer to manufacturer; however, most are between 3 to 8 years, regardless of mileage. The National Transportation Safety Board (NTSB) and some tire manufacturers are recommending that all tires older than six years should be replaced, regardless of their condition. Tire manufactures are required to label each tire with a DOT Code on the side wall which says when the tire was made. The DOT code is 4 numbers, the first 2 are the week and last 2 are the year. A tire stamped DOT 5012 was made in the fiftieth week of 2012 and should be replaced regardless of the tread depth and condition.