Trailer Tires...A Camper's Biggest Friend or Foe

There's a lot to be said about tires for campers. They can make or break a trip. You always want to go through a checklist before a trip. But there's a couple things you need to consider with tires whether you own a trailer or are looking to buy one. The first thing to understand is that trailer tires take more abuse than car tires due to trailer bounce while driving. Also, they sit a lot when not being used. So trailer tires are more likely to dry rot before the tread wears out. So lets talk about two topics related to tires: how to tell the measurements/size you need, and how to tell how old a tire is.

Tire Measurements

There are a lot of numbers/codes on a tire. They all give you some information about the tire itself. Most folks are familiar with something like P225/70 R15 on your car. This is the type and size designation of the tire. P at the beginning stands for P-metric (or passenger car in the US). It's never a good idea to use P-metric tires on a trailer. They aren't designed for trailers and if you put them on a trailer you can't go by the load capacity on the tire. LT (Light Truck) and ST (Special Trailer) tires are typically used on trailers. So you should look for LT or ST for your trailer.

The second part of the code (225 in this example) is the measure in millimeters from sidewall to sidewall of the tire. The third part of the code is the aspect ration which simply means the percentage of the height to the width of the tire. Basically the bigger the number here, the taller the sidewall. R stands for radial (which is most tires today). And the last digit is the wheel/rim diameter that the tire is supposed to fit. There are plenty of information on tire websites that goes into more specifics but that's the basics on tire size. My tires on the U-Haul are ST175/80 R13.

If you buy an old camper, you may find Bias Ply tires rather than Radial tires. They are sized differently. Your best bet is to take the tire/ or the numbers on the side of the tire to a tire store to get a replacement. Bias ply tires have been phased out over the years in favor of the softer ride of radials.

How old is my tire?

Knowing the age of the tire is just as important as looking at the tread (especially for those of you buying a camper who may have to drive it a ways to get home). If you want to know the gritty specifics on why tires dry rot, ask your friend who took chemistry in college or Google it. Basically, think of old rubber bands, The oils and chemicals in the rubber break down and some evaporate over time and the rubber gets more brittle. This makes it more prone to cracking and blowouts. A big cause (or accelerator) of this is UV rays from the sun. For those who are new to campers, you probably thought those tire covers on other campers were just for looks or to keep the tires clean. Not really. Veteran RVers know that shielding them from the sun will make them last longer. You may even want to get a cover for that spare tire to make it last longer.

All tires, in the US at least, are manufactured with an Tire Identification Number (TIN). The same code is stamped on every tire in a batch. The TIN is the code after the DOT part on the tire. as you can see in the picture on the right from my tire. What we care about is the last 3 or 4 digits on the tire. For tires made before 2000, there will be 3 digits at the end, for those made after 2000 it's 4 digits. So right away if I bought a camper with there being 3 digits only at the end of the TIN, I'd go get a new tire. For those made after 2000, the 4 digit code is easy to read, the last 2 digits are the year the tire was manufactured. That will tell you how old the tire is. (The preceding 2 digits are the week of the year.) So in my example to the right, This tire (my spare) was made during the 16th week of 2012 (1612).

So now you know how check your tires. I can't stress how important this is for those buying used or vintage campers to look at the dates on the tires. When I bought our U-Haul fiberglass camper, the tires on the camper were decent age but the spare was a bias ply that was probably 20-25 yrs old. I replaced that the first week as my very first "project" on the camper. I just wasn't comfortable trusting that spare if I needed it. Oh and always carry a spare! If you are buying a camper and it doesn't have a spare tire, then I'd recommend trying to find one before you go on a trip.

I hope this helps some of you. Feel free to drop me a line or comment below if you have any questions.