The average life of a tire is five to seven years. If you drive a vehicle every day, you'll probably wear out the tread in less than five. RVs spend most of their time sitting still. So your tires will probably need to be replaced before the tread wears out. Maybe it's cracks from the sun or maybe it's sitting too long with too little air in them. When your tires hit fives year in age, it's time to think about replacing them. It's even more important with the kind of weight and load that your RV puts on them.
Every tire has this code on the sidewall. It gives the date that the tire was manufactured but it doesn't just spell it out right. You have to know what to look for and how to read it. It'll be something like this: DOT PDML AZOF 0508. It's on one side of the tire, so you may have to crawl underneath to look at the inside of your tires. The date code always starts with the letters DOT and ends with a 3 or 4 digit number. The first two numbers indicate the week of the year. 52 weeks in a year so that is the max. The last one or two digits tell you the year. In this example, 0508 means the 5th week of 2008, or the first week of February 2008. With the year 2000, the date codes have two numbers for the year. Only one for years before. A date code of 157 would indicate the 15th week of 1997 or you are lucky to be alive if this tire is still in use.
Ask to see this number when buying new tires. You really don't want to pay full price for a tire that has already sat somewhere and deteriorated for a year. You probably won't get one that was made last week, but you should expect it to be within the last several months. The tire dealer may look at you as an oddball or pretend to not know what you talking about. That's when you check the number or get ready to find another dealer.
If you've bought new tires or looked at your own, you'll see the mess of letters and number on the sidewall. It could be like this one my smaller RV.
LT 225 / 75 R 16
Type - Width / Ratio of width to sect height - Radial - inside diameter
The first letters indicate the type of tire: P for passenger car, LT for light truck, and ST for special trailer. You won't find anything special for bus and medium-duty truck tires. The number 225 in this case, is the width of the tire, given in millimeters, followed by a slash. The number after the slash is the ratio of width to section height. Then you have a letter. R for radial ply or D for diagonal (or bias) ply. That is followed by a number which gives the inside diameter of the tire in inches.
The load range of a tire is a letter, A through E, and is on the sidewall of the tire. You will want to make sure you get the right range rating for your type of trailer or RV.
How Do I Decide?
The easiest way is to start with what is already on your axles, assuming these were the new tires from the factory. If you were not the original owner, then you should double check the vehicle plates and documentation for what should be on the vehicle. Someone may have put the wrong tires on there before you. If specs and everything checks out and they have done well for you, get another set of the same. You can probably find the same tire or a newer equivalent. Or you may want to ask what is the next best step up for the same tire. Or get the same specs on a tire of another brand. Don't jump wildly based just on price or brand. Start with the current specs and see what is available.
There are many different tires out there because there are many types of vehicles and uses. Passenger car tires are more for a soft ride on your daily drive. They grip the road well and are for your average weather situations. Light truck tires are built with stiffer sidewalls to carry heavier loads. They are also for daily use so they have decent handling and are fine in average weather and storms. When you get into trailer tires, you can expect them to be designed for a soft ride and some give to slide sideways. You should stick with trailer tires on trailers. Don't truck tires or off road tires on a trailer just because they are better or more expensive. They are not designed for the unique needs of trailer loads and handling.