Fuel mileage vs. inflation pressure?
Kevin crows about super high tire inflation pressures increasing fuel mileage. What are the numbers? I run 50% empty miles with spring ride trailers and I can immediately tell the ride is much harsher @105 psi instead of the 85 psi I have used for 25 years. I pull 2 or 3 different trailers every day and can't measure any differences in fuel economy with accuracy. It seems the fuel mileage difference is much smaller than the ride difference.
Same theory if your riding a bicycle and you lower the pressure in the tires it becomes harder to petal because there is more surface making contact with the ground so if you air the tire up tight it's easier to petal due to the fact there is less surface making contact. Same theory on truck tires if they are aired up to the maximum they roll freer thus better fuel mileage. If the ride is more important lower your pressures to 85 and wear your tires faster.....
I agree with blackwood it does change the footprint weather it changes MPG if any is very little. But tires are designed for a certain footprint on the ground and when you change that footprint either by over inflation or under inflation your going to have irregular tire wear plus when you change that footprint you run a higher risk of hydra-plane. You would be better off using the mfg air pressure guide for the weight you carry on the axle
Tire wear increases 20% for under inflated tires but only 5% for over inflated tires. Higher pressures reduce the flex in the sidewall which reduces heat too. In hot weather you should keep your tire pressures high. Conversely, cool weather lowers the air pressure which could cause heat and a blowout, so in cool weather you should keep your pressure high. Moral of the story, higher pressures are always better for your tires. Better fuel economy is a side effect.
Any numbers put out by the manufacturers are minimum recommended pressures. That includes what's on the sidewall of the tire.
This info was provided by Mike Beckett of MD alignment at the 2013 CMC. Mike works with tire manufacturers and engineers directly to diagnose tire wear issues. He is an expert in the field.