Paradox: Overinflating tires = Lower MPG over the long term?

[Nativechief]

Originally Posted by ragnarkar

My idea of overinflation is pumping it to 40 when the max allowed is 44 and the manufacturer's recommendation is 40.

I've been told it improves MPG for now and makes the treads wear faster.

Now, my main question, still unanswered is:

Will I get less MPG once the treads wear out faster? The cost of tires isn't a huge issue since they cost roughly the same as fuel for 2-3 months and they're supposed to last 65K miles.

Your answer is NO

[Mac_Muz]

Originally Posted by cdelena

I used to race sports cars (street legal R-compound tries) and would start the day with 28psi and would have to pit in a few laps to reduce the pressure (back down to 30) because it would climb over 40psi (heat build) which would give less traction. Transient temps can climb 50% for short periods under heavy loads.

Even though drivers often prefer higher pressures because they feel more responsive at moderate speeds the real fact is they have less grip and the vehicle will lose traction more easily. The best inflation most of the time is what the vehicle manufacturer recommends.

Over-inflation offers more disadvantages than advantages.

I did to and some races, and i can't spell the word Gym Kant'a a race around pylon's (orange cones) everyone was required and tested to be set at no less than 60 psi. This was so in hard turns the tires would not slip off the rim.... It wasn't about handlings, or saving gas, just about not loosing a tire off the rim.

After the rce for street cars you dropped to stated vehical psi or tire related info.

That was a long time ago, and I have tires where that 60 psi is well over max tire psi today on tires I own.

[cdelena]

Originally Posted by Mac_Muz

I did to and some races, and i can't spell the word Gym Kant'a a race around pylon's (orange cones) everyone was required and tested to be set at no less than 60 psi. This was so in hard turns the tires would not slip off the rim.... It wasn't about handlings, or saving gas, just about not loosing a tire off the rim.
...

Must have been something about bias-ply tires years ago. I don't think you could get a normally inflated radial tire off the wheel on any lateral load.

[Mac_Muz]

I can't recall what tires we had exactly then... I think radials were just coming to market.

[dhanu86]

I keep mine inflated 35psi, 40 if I have a load on a long trip, but to dampen potholes I think its best to use the recommended psi. Its better to overinflate than under inflate for tire life. Just don't go over the maximum psi read on the tire. And remember to measure when the tires are cool, otherwise the reading can be 6 psis off. And rotate them..

Rotate them, if the car is old might want the bushings or shocks checked, check the pressure every month, don't let them stay underinflated.

[ralphfr]

The answer is no. The only thing that will change you MPG is the actual circumference of the tire. Lower inflation means a smaller circumference and less MPG. Friction will increase but the degree is debatable.

[stilldriveem]

The owners manual for my 79 T-Bird (which calls for 30 psi front and rear on the door tag) also says if you were going to be driving at 75 mph or more for one hour or more, you should add 4 psi to the tire unless a 4 psi increase exceeded the maximum inflation pressure stamped on the tire's sidewall. That no doubt was done to prevent excess heat buildup. So perhaps a little overinflation does help. The thing I can't figure out though, the car had it's original spare (a Michelin X Radial) that was stamped with a maximum pressure of 35 psi and 1820 lbs of maximum load capacity, which used to be referred to as Load Range B. The new Hankooks I bought in '15 in the modern day size equilvalent still are only listed as 1820 lbs of load capacity but at a maximum inflation pressure of 44 psi. So why have maximum tire inflation pressures increased over the last few years over what they were for years prior? Anybody know?