On tire pressures, the Yaris, and the Prius

[1stToyota]

Originally Posted by sbergman27

The 0.3% fuel economy per 1 psi rule of thumb applies to underinflation. One would expect to see diminishing returns as one increases the pressure above the placard values. Plus, I would expect to see a significantly shallower slope (less return per psi change) for the Prius' LRR tires than for regular tires.

Increasing and decreasing pressure is a trade-off, even between the placard pressure and the sidewall pressure. The tire probably won't fail under normal conditions. But impact resistance of the tire *is* reduced. Shock stresses on the wheel *are* increased. (Think "bending" in the case of steel, and "breaking" in the case of alloy.) Shock stresses on suspension components, such as the strut mounts, *is* increased.

It's not the normal driving that is likely to get you. It's that shear 4 inch transition you hit in the construction zone, where the not yet repaved road meets the newly laid concrete, that you absolutely were not expecting.

I used to run my Sprint at 44 psi... and did sustain wheel and strut mount damage.

And, of course, stress on nerves and dental fillings is increased.

-Steve

True, and what would probably worry me most is being forced to do a panic stop and getting to skid and crash due to the fact that stopping distance would be increased when tires are overinflated to 60psi, and mine didn't come with abs brakes.