Recommended ST225/75R15 Trailer Tires for 31-Ft 5th Wheel to Avoid Tire Blowouts

Question:

What is your recommendation for new tires on a 31ft 2001 Forest River Wildcat 5th wheel camper. Double axle. Right now we have Maxxis radial M8008 ST 225/75R15 on it Load range E. Two are new this year and two are from previous 2 yrs. We have blown several tires and are tired of this. We are wanting to go to a higher load range and possible bigger tire. What advice can you give us.

asked by: D

Expert Reply:

A trailer tire's worst enemy is heat. Excessive heat will weaken a tire and lead to its premature failure. The most common causes for a trailer tire to overheat are overloading it beyond its rated weight capacity and incorrect inflation pressure.

If you replace Load Range E tires with F- or G-rated tires their higher weight capacity will tend to mean reduced operating temperatures, all other things being equal. And of course, all trailer tires should always be inflated to the maximum pressure as noted on the tire sidewall. It is never appropriate to over- or under-inflate a trailer tire.

Note that your trailer's wheels will also carry weight and psi pressure ratings, just as your tires do. If you mount a tire on a wheel and the two have different ratings, then the lower-rated of the two will determine the overall capacity of the combination. So in other words, mounting a 2000-lb rated tire on a 1500-lb-rated wheel results in a combination having a 1500-lb rating.

In your ST225/75R15 size we offer tires in load ranges C, D and E but not higher. Our load range E tire in your size, Kenda # AM10303, carries a maximum weight rating of 2,830-lbs at 80 psi. The Maxxis M8008 ST225/75R15 radials (their part number TL15710000) according to their website have a weight rating of 2540-lbs. If this is the tire you're using then you could gain a worthwhile safety margin by switching all tires to the Kenda above.

You could also potentially move up to a larger wheel and tire size if your trailer has enough clearance. A ST225/75R15 tire has an overall diameter of about 28-1/2-inches. An ST235/80-16 tire has an overall diameter of about 31-inches, and of course it is 10mm wider. This is a fairly big jump so I'd advise checking with Forest River (using your trailer's VIN) to see what have to say about using this much larger a tire size. The Provider tire in this size that we offer, part # TTWTRTM2358016E, carries a Load Range E rating of 3520-lbs at 80-psi.

expert reply by: Adam R