I know it's a stupid question. But guess what? Nobody has a real answer.
Yes, the vehicle manufacturers have been mandated to post the recommended tire pressures on each vehicle but why did they have to do that?
Yes, it's from the result of high centered small trucks flipping over from too low tire pressures and I can understand many owners don't read the owners manual or even think of checking tire pressures, so it has to be posted on the pillar possibly for liability reasons and that may be excellent for factory equipped tires. But, in posting the recommended tire pressures on the post is creating some problems.
What happens when the tires are replaced with a different brand and different construction?
Keeping to the factory pressures could undermine the tire manufacturer's design for stability and handling characteristics and could be considered "under inflated" or "over inflated" depending on the new ties installed. We see this on cars but especially on light trucks where a 'P' (passenger) series tire with a factory recommended tire pressure of 30psi were replaced with an 'LT' (light truck) series with a maximum tire pressure rating of 55psi or even 120 psi.
I posted this topic to the members of IATN and the majority were convinced that the posted tire pressure was correct and to be adhered to.
I really disagree.
One technician wrote;
"Maybe an actual tire expert can verify, but I do not think your argument is correct. Just because the replacement tire has a higher maximum pressure, it does not mean it cannot be run at the same pressure as the original tire.
Perfect example is the tires on my Tahoe. The door sticker says to run them at 35, yet both the original and the replacement tires that I have now both have a max pressure of 55. For normal driving, I leave them at 35. If I am going to be towing, or putting a bunch of bricks in the back, I raise the pressure to the maximum.
Like I said, I am certainly not a tire expert, but I do not think that the maximum pressure has anything to do with the ability to run the tire at a lower pressure."
That comment appears to be completely contrary to the advertised warnings they are giving the public about under inflated tires.
I don't think he would adhere to the factory specs if he had chosen BFG All Terrain T/A 31x10.50r15LT that has a maximum pressure rating of 32psi and the vehicle sticker posted recommendation is 35psi.
Or, what about the opposite end of the scale when the posted vehicle sticker says 55 psi front and 80 psi rear?
I completely agree with adhering to the factory recommended tire pressures with the factory supplied tires, but when the tires get changed to a different brand with different specifications, all bets are off.
And then there are the legal ramifications;
Ultimately we. as businesses and licensed technicians, are legally responsible for the products and services we apply to a vehicle and we can be held liable if our actions are proven to have contributed to an 'incident'.
Let's get the tire manufacturers involved with this. They must have a simple guideline that's based on some common sense we can all use and pass on to all of our customers.
It's one of those things everyone assumes everyone has an answer to.
What's your opinion?
Oh and by the way. Remember the incident that started all this? Yes, it was a Ford Explorer. The tires that were on that vehicle were passenger tires (P series). Who, in their right mind would think of putting soft sidewalled passenger tires on a truck, especially one with a short wheel base and high center of gravity?
Oh, I'm sorry. It was the manufacturer. I guess because it was cheaper, they wanted to get a car ride and anyway, the other truck manufacturers are doing it.
I guess putting stickers on vehicles is a lot cheaper than doing a full recall.
