I recently put 4 Michelin LTX A/T2 on my truck. I emailed Michelin from their Web site to ask about adjusting tire pressures based on load. I normally carry one set of pressures with the Lance onboard and another when I'm unloaded. I never carry the max pressure of 80psi because I have never reached the max weight of 3750lbs per tire.
Within the hour a nice lady from Michelin called me and stated unequivocally that I should stick to the pressures Ford recommends on the door post. I explained that my rationale was based on standard load/inflation tables for E rated tires but she again stated that I should use Ford's numbers. What do you think and why?
unless they are the OEM tires, with no load, I wouldn't stick to what the door sticker says.
Your carrying a camper sometimes and that would be dangerous.
She spit that answer right out of the Lawyers handbook.
I always adjust the pressures to what my contact patch tells me. I do the chalk across the tread test and adjust my pressure acordingly.
Keep doing what your doing.
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Most folks don't even know about tire inflation charts any more. They just know the door sticker and tire max. I'll bet the lady from Michelin isn't used to dealing with truck tire or folks who know something.
The door sticker usually has the pressure for the max load of the vehicle. So, if you are running empty, you could go lower if the tire inflation chart suggest it.
For cars, I usually run door sticker +2 to 4 pounds, other wise I wear the edges too fast.
For trucks, trailers, or any other equipment where I'm running loaded, I ALWAYS use max tire pressure. The additional pressure provides better stability and fuel mileage. Plus, I've never seen a tire blow due to having the max rated pressure, but have seen plenty blow due to under inflation.
The negative side to running max pressure is you get a bit harsher ride and the possibility of wearing the center tread faster than the outside.
I've run my truck for the first year of towing going between two different pressures. Since then, all four of my tires are always at max pressure of 80psi. Trying to switch back and forth, I started wearing the valve stems out. I do not use the truck in any commercial aspect, but between the horse trailer, 5th wheel, gooseneck flat bed, and now the TC, I'm never sure when I will be moving something needing the extra pressure.
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It's called Liability! Michelin will state what the max cold pressure the tire can hold on the sidewall of the tire. But every tire manufacture will always tell you to follow your owners manual for your tire pressure specifications.
My opinion??? I'd record that conversation and for my next flat tire, I'd use it to sue their pants-off for pun'e'tive damages. Yesirree that's what I'd do.... what's their phone number?
IMHO,
Chalk test and weight formulas will only get you close.
Weight of vehicle
--------------------------- x Max tire PSI as indicated on sidewall
Tire max load rating (lbs)
multiplied by 4
In my experience both will yield under inflation.
Weight charts get you a lot closer and many times indicate less pressure than door sticker or tire label.
Applying some some common sense derived from the above indicators, for LT truck tires, I run 5 to 10 pounds under the door sticker for a softer ride.
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Big Katuna wrote: I think there was a lawyer standing behind her.
Ditto this thread and the previous one before it. Its all about liability. No one is going to tell you or put it in writing (lol), that it's OK to adjust the tire pressure based on load. Because if you have or cause an accident the insurance companies are going to put the blame on someone. Most likely it will be the one with the deapest pockets.
I tried getting this information from our local Ford dealer in Puyallup. The service guy told me to go by the door sticker pressures, which I'm not using without a load.
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