Quote:
Originally Posted by JRTJH
Years ago, every truck owner's manual had a tire "weight/air pressure" chart in it. During the "dummy down" that occurred when soccer moms started driving crew cab trucks and many owners didn't want to be "bothered with facts," that chart disappeared and the information for a "one size fits all" door sticker appeared.
My tires have a max single load of 3640 at 80 PSI and a dually load of 3305 at 80 PSI. My rear axle (single) is rated at 6100 lbs, so theoretically my tires would be rated at 7280 (1180 pounds over the axle rating) if I ran them at 80 PSI. The actual weight on my rear axle is much less than that when not towing and closer to 70 PSI (per the chart) when hitched to my fifth wheel. The only way to "really know" is to run across a scale.
I'd suggest finding a "weight/air pressure" chart for your tire size, weigh your axles (front and back) with the truck as you normally drive it, find the correct air pressure for that weight (for the empty truck) and then weigh the axles with the trailer attached and find the correct air pressure for that weight (for towing). There will be minor changes in those weights with every tow, but they should be "close enough" for most applications.
Some people use the "chalk test" to determine if the tread is "flat against the concrete" or monitor "center/edge tread wear" (sort of an after it's worn test). Some will suggest you "max out" the tire when towing (better sidewall rigidity) and some will suggest "just find a happy medium" and don't worry about it.
I think knowing what weight is on your axle and adjusting the tire pressure for that load is the most reliable. Others may have different opinions.
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Much better and well thought out than what I do.
