QuestionI have a Chevy Express conversion van that weighs 7100 LBS. The factory seize is p235/75/15 (XL). It has 255/70/15's on it how but with 7" wide wheels, they swim side-to-side.
My question is: Why do LT tires Carry less weight than do P metric tires, even if they are the same seize? It seems that I have to sacrifice load bearing capability for a heavier tire side wall. Which would be best load range C, of P metric service desc.
AnswerBrian,
Your last question first: Stay with the tire size the vehicle came with. If it came with P metric, use P metric.
The story behind LT metrics and why they carry a lower load than P metrics is relatively long, but I'll give you the short version.
P metric tires, when used in a Light Truck application (Pickup, Vans, Trailers) have to be derated by 10%. That explains some of the difference.
But LT metrics are the little brothers of the large Over-The-Road truck tires, so when they were brought into existance a long, long time ago, these guys followed what worked for Truck Tires - low deflection = high durability.
At the time cars and trucks were clearly separate vehicles and the tires did not overlap. Well.....time has marched on and people are using trucks like cars and they expect them to ride like that. So the tires now overlap, and this results in this odd situation.
But you should be aware, that LT metric tires are tested according to the LT metric rules and so using an LT metric in place of a P metric has a risk associated with it, and knowing that, I can't recommend they be used interchangeably.
