Ok, I get it. But that isn't what we do on our passenger cars and trucks. My Michelins for example on the car are rated max cold at 44 or 45 psi, I forget. But even the tire shops won't fill them, nor will the dealer, to their max cold rating. I keep 40 psi on our Prius because it creates a stiffer tire, resulting in a lower rolling resistance. The rating on those is around 44 psi too. I get that it is a fine line between under and over inflated. But I don't get the mystery. Why doesn't a manufacture just tell you what to inflate them to period? I'll tell you why...because they have no idea what weight they will be carrying, and they are designed to carry a weight range, not just a set weight. Did you know that a tire on a dual wheel setup is inflated lower than a single tire/wheel setup on the end of an axle? It is. Why? Because it is about the weight the tire carries. The heavier the weight (up to the max certified by the tire manufacturer), the more PSI you put in it. Why? Sidewall flex. You want the same sidewall flex at the low weight as at the heavy weight. Now, bias ply and radials are different animals and designed in different ways. This thread is pertaining to, and I will change the title, bias ply tires on trailers. Not that I am not interested in others, but the stock tires on our trailers are bias ply. That said, many have switched to radials. The more I learn about tires, the more I wonder about that decision. And the main reason I wonder is this...the weight range on a radial tire is tight, much tighter than a bias ply tire. A trailer is designed to carry a load. A truck or RV is designed to carry a load. If you drive in the city in your truck all the time with no load in it, you should be carrying less PSI in your tires than you do if you drive that truck at its max GVWR. I don't alter mine often and I don't know anyone that does unless they are at the extreme end of the spectrum. But on an RV, trailer, or other weight varying vehicles, you need to weigh them, each axle, and one side of the unit, to get the individual axle weight and assure distribution is equal across the axle. That isn't something the average guy pulling a trailer will do either, but he should, especially on a long journey.
This is a good discussion. Now I need to consider getting my floor jack under the trailer on the side of the road! We will see a good many two lane roads on this journey, and you can't pull off the road in a 39' motorhome...unless it has a paved shoulder. I like to be prepared and not push a bad position. I think a trailer tire that is 3 years old, only been dunked a couple of handfuls of times, has been stored indoors, and has less than 1000 miles on them should be able to go another 2000 miles easily. They don't have any sun damage or weathering, and they certainly can handle the distance, but after this trip, I expect I will be buying trailer tires for sure. So, bias ply or radial, that will then be the question. On that subject, a smoother ride isn't necessarily the safest ride, but a bouncing tire isn't safe either. Ok, enough, don't overthink this! After Powell, where on earth would I trailer the boat? PNW, Florida, Table Rock...we better make an informed decision, this is a trailer boat! Glad you guys have helped my consider all the angles!
