tire pressure vs fuel economy

pianotuna wrote:
Hi Drewe,

That flies in the face of my real life measurements. 20% is not a small or insignificant change.

I do agree that head winds are not something you wish to drive in all day long.

I just don't believe that tire pressure could result in anything like a 20% change. Something else had to be going on like wind, speed, mountainous terrain.

pianotuna wrote:
Hi Drewe,

That flies in the face of my real life measurements. 20% is not a small or insignificant change.

I do agree that head winds are not something you wish to drive in all day long.

I don't doubt your measurements, but I do very much suspect the tire pressure change is mostly coincidental and not the primary cause of it. I would generally expect to see a change of at most a few percent. (I also may be wrong; it wouldn't be the first time, and likely not the last either.)

I'd personally go with whatever pressure gives the best handling and ride (and is within the limits of the tire for its load, of course).

Yea I don't see much in the way of wear issues on steel radials like the old nylon bias used to be for running a bit high on pressure. I tend to run max sidewall pressure in all my vehicles with no issue. In fact going with lower oem pressure seems to scrub the front edges a bit.

Headwind does hurt far more than a tailwind helps. Wind resistance is an exponential function.

Hi Drewe,

That flies in the face of my real life measurements. 20% is not a small or insignificant change.

I do agree that head winds are not something you wish to drive in all day long.

Within reasonable (i.e. safe) limits, the difference in tire pressure for an RV will not make a noticeable difference in fuel mileage. Most of the fuel goes to overcoming air resistance and (on hills or in cities) hauling the weight around. Rolling resistance of the tires is negligible in comparison. If your tires are wildly underinflated, of course, that's a different matter, and probably in that case gas mileage is the least of your concerns and costs.

Widest contact spot is BEST for traction AND braking.

Those are the two parameters I try to maintain

55 psi on fronts all the time gives me the most contact spot
45 psi on rear when not towing and 80 psi when towing

Just takes some sidewalk chalk and a little time to find that spot.

Hi GordonThree,

for a 1000 kilometer trip = 300 liters

300 / 0.8 = 375 liters

Currently I'm paying $1 per liter

So the savings are $75 per 1000 kilometers.

Cost for a pair of tires is $588.00 installed and balanced.

I wonder, which saves more money, increased fuel economy or increased tire life?

tires aired too high or too low for their load will wear faster, due to less than optimal surface area contact, wearing out the outside or inside tread faster - new tires are expensive and could evaporate any savings from milage gains.

Strictly speaking running high pressure narrow and bald tires will yeild high fuel economy numbers than low pressure knobby tires.