It's hard to write about tires and keep it short, but if my "summary" isn't enough I'll lengthen it later. Sidewall failure (blowout) in a trailer tire is always an exciting event (I've been there), and not in a good way. Traumatic failure is caused by a puncture or bruising, i.e. hitting something hard, but the most common failures are non-traumatic. There are three factors for non-traumatic sidewall failure: applied force (weight of the trailer), age of the tire, and heat. These work together, so the heavier the load, the older the tire, the less heat it can handle. Every trailer owner will find his/her own comfort zone on tire age, but my absolute limit is six years. When a tire reaches its DOT manufacturer's date (stamped on the sidewall) plus 6 years, it's time to go. It does not matter what the tire looks like on the outside. See wmtire's post on tire age. Heat is caused by the "flexing" that the sidewall does when its rolling down the road. All tires generate heat when rolling, but the heavier the load, the less they are inflated, and the faster they are rolling the more heat they create. A final variable in heat is the ambient air temperature, as this affects the tires ability to dissipate the heat it is generating. So, finally, to MarkoPolo's question: if you're traveling on a dirt road at 30 mph and it's 70 degrees or so, putting 50 or 55 psi in your Marathons will probably have little impact on sidewall heating. But if you're traveling at 65 mph (the maximum recommended speed by Goodyear) on six+ year old tires on a 95 degree day, I would strongly recommend you inflate to 65 psi...and keep checking your side mirrors for possible excitement!
|