Always the car - never the tires...The tires will only tell you the max
pressure. You'll find the info either in the book or easier yet,
usually on the drivers door jam on that sticker you pass every time you
get in and out of the car and never look at. :)
Different models, different tire sizes, different option, etc. That is
why they put a sticker on the car....
If Ford thought they'd get a measurable imporvement in mileage, it is
likely they would have already upped the specified tire pressure. The
EPA uses the recommended tire pressures when running the gas mileage
tests and Ford wants every tenth of an mpg they can get to improve the
As for handling......well it will feel different with more air in the
tires but higher pressures do not necessarily translate to better
grip. If you like a stiffer ride, then adding a few psi probably won't
hurt anything (assuming you stay below the maximum allowed pressure as
indicated on the tire), but it won't necessarily improve you actual
handling (as contrasted to precieved handling).
Car companies spend a lot of time trying to come up with the best
compromise tire pressure for their vehicles. They have to consider
Customer perception, safety, fuel economy, tire life, etc. The
pressures recommended are a compromise. My guess is that safety is the
#1 factor, followed by fuel economy, Customer perception, apparent
handling, actual handling, and tire life in order. And since currently
Ford only recommends a single pressure for all load conditions, I am
assuming the recommended pressure area already higher than optimum for
the other fators (higher pressures are best for safety and fuel
economy, but maybe not for the other factors).
Extra air in the tires can make a car feel like it is handling better.
I just added a couple of extra psi to my Fusion on Sunday becasue I
figure cold weather will soon set in and drop me back to more or less
the correct pressures. The car "felt" tighter. I doubt it actully had
more grip, but it did feel different.
2002 Taurus door jam, and other sources, show tire pressure is exactly
What would happen if I went to 35-39 PSI?
Would it improve gas milege?
At what PSI would the MPG start to drop off the charts?
As a teenager I had a 1977 Cutlass Supreme and the tires were spec to
35 PSI and just for fun I gave them 45 PSI and friends and I laughed
since it made the can take any imperfection on the road seem like
going over deep train tracks at 80 MPH, plus it wore the tires out
freaking fast, about 6 months and they were shot on the edges.
Don't know if the gas milege was better or worse since I didnt give a
damn because gas was so damn cheap as percentage of disposible
Over inflation would tend to cause the tire to run on the center rather than
across the full tread width. Causing wear on the center rather than outer
edges. Under inflation causes the effect you describe.
Read the specs on the tire and compare to car manufacturer
recommendation on door jam. If you stay with specs on tire you should
be OK for footprint. But going more psi than car manufacturer will
compromise handling as psi is matched to suspension components.
On Tue, 06 Oct 2009 13:54:58 -0400, Pedro Sanchez IV
Don Byrer KJ5KB
Power & Glider Pilot Guy
"I have slipped the surly bonds of earth; now if I can just land without bending
"Watch out for those doves...<smack-smack-smack-smack...>"
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