Tire pressure?

[4MPG]

Originally Posted by BailOut

Increasing tire pressure increases handling, traction and tread life as well as mileage. I run mine at 60 PSI, as do thousands of other hypermilers.




Fuel efficiency is all about many tactics adding up to significant gains. Tire pressure is one of the larger factors.

more pressure may increase mileage, but it sure as hell doesn't increase handling/traction or tire life.

your getting better mpg because you have less tire contact on the road (less resistance) and less flex (wasted energy). However, this also results in less traction and poorer handling. It will also reduce tire life by wearing the center tread faster, since it takes all the wear instead of spreading it over the entire tire... you will get a bald center with tread still on the sides. You can see a picture of this at almost any tire store, as they usually have them posted up along with the reason for it happening and what causes it etc. While overinflation might result in a drop in tire temp, the center wear will outweigh any benefit.

If you want even more proof, especially on the traction side, visit any local dragstrip. You will see all of the "street" cars lowering tire pressure after they arrive, and almost any dragstrip worth its salt has a compressor so you can bring them back to road pressure before you leave. The drag radials on my mustang are particularly sensitive to tire pressure, going from 25 to 20 PSI resulted in nearly a .2 second faster 60' time. Even on my buddies T/A, with stock goodyear regular radials, he was regularly picking up .1 in the 60' with a 5-8 PSI drop from his street pressure.

For traction, and to a lesser degree handling (gotta keep the pressure up enough to keep the sidewall fairly stiff) you want a lower than standard pressure, not higher. You want as much resistance as possible, as resistance is what gives you traction/handling, and to achieve this you get as much contact patch as you can. The basic idea is to lower the pressure to the point that you have as much of the outer part of the tire in contact as possible, without causing the center section to actually start rising from the road (too underinflated).

Edit: To answer the poster above me, to get maximum tire life your probably going to want to run your tires a few (3-5) PSI higher than the doorjam recommends. The doorjam takes into account the best PSI for the tire, but it also takes into account that a lower pressure will result in a better ride (soaks up more vibration/bumps etc).