Awhile back, established at this newsgroup that AC compressor use does
affect gas mileage in small vehicles like an older VW with small engine.

How drastically can tire pressure affect gas mileage in similar older VW
with small engine (1.8L)?
An example. Recommended tire pressures by VW. These are part ot the
suspension system, and provide comfort for the driver and passenger. No
where near the max 32 psi of same tire. What if you max hot pressure to 32
psi? What if you're running around with 15 psi for instance instead?

Reason I mention is for 2 reasons. One tire (LH front) has a very slow
leak. Have to refill every 2 months. I've gotten used to this, rather than
having it fixed. The other reason is the two tires on the RH side decided
they were going to go low, almost flat. Don't know how long they were like
that. I did notice greater difficulty uphill, faster deacceleration letting
off the gas pedal, and sloppy/wishwashy rearend movement at any highway
steering movement. Upon refilling the RH side tires, and roadtesting,
noticed opposite. Easier to climb hills, slower deacceleration, and tighter
rear end movement. Am guessing the low pressure contributed to sidewall
movement of the tires in turns. Pressure gauge starts showing around 20
psi. The RH tires could not move that gauge when low. Am considering 32
psi all 4 tires.
--
Jonny

A few things. You read 32 psi max on the TIRE. That applies to the tire
manufacturer. They have no idea where the tire is going to be used, you
could be using it on a skidoo trailer, or hauling a trailer with a cord of
wet wood. It has nothing to do with a car.
VW says, after doing their road tests with the car, whatever tire you
put on put this amount of air in for max.tire life, comfort and good
handling. That is, the psi is according to what the CAR weighs front and
rear.
Now, from experience, if you are running too low an air pressure, you
are most likely gonnna experience a sidewall blowout, as the sidewall will
be flexing more than it usually does which builds up heat and causes the
failure to happen. So, keep that pressure up.
As a maximum, heck my spare has 50 in it.
But, if decide to run your air pressure at the high end (whether that
be 35-40 odd), it will give you better fuel economy, but, you do lose
traction as the tire will be wearing out prematurely in the centre of the
tread....also you will feel like you are riding on the steel rims
themselves when you hit bumps. You will have more get up and go with the
higher tire pressure, which shows you that if you got a flat, you need more
power to turn that wheel over as it is not so round as it once was.
Do yourself a favour and get the tires fixed(you probably have a bead
leak, which means they have to dismount the tires, clean the rims and
remount again. And they (the tire shop)will stuff 32 in(or more) right
away so that the bead seats itself to the rim, you can readjust the
pressure later(a couple of days of driving on them)

The 32 psi has been used on large Chevs and Fords for the longest
time, so it is a number stuck in the shops head. If you check in the
newer chevs, ford, bmw's, toyota's, they all have different numbers for
the tire pressure(even though the tires(most brands) say 32 max).
WW

Me personally, I find that high tire pressure beats the cars suspension to
death and starts the cars creaking and groaning after a year or two. If I go
cross country , or have a load I go 32, Everything else #30 rides real nice
and doesn't eat tires up.
"wrenchwench" <beesser (AT) hotmail (DOT) com> wrote

Why not just replace the tires or fix the leaks? Then there's no need to
worry!


"Jonny" <spamyourself (AT) blackworm (DOT) net> wrote

A tire with incorrect pressure will wear out much faster, but worse than
that incorrect pressure can lead to loss of control.

As noted, the pressure on the tyre is the max for that tyre not the
recommended pressure for the tyre on your car or any other car. You look at
that just to make sure it is equal to or greater than the pressure you
intend to use. Don't use it to determine what pressure to use.

The manufacturer has recommended a specific pressure for the original
equipment size tyres and had done so based on a number of controlled test
tract test. Going much over or worse yet under the recommended value can
cause unsafe handling.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math


"Jonny" <spamyourself (AT) blackworm (DOT) net> wrote

Affects gas mileage in all vehicles, regardless of vehicle or engine size.

A couple of percent.

Quit screwing around, and get your tires fixed! Why put up with the
problem?

Don't know how long they were like
You demonstrated to yourself how much low tires will affect fuel
mileage. If your handling was getting loose from low tire pressure,
you're lucky you didn't have an accident. Get the tires fixed!

Upon refilling the RH side tires, and roadtesting,
You could try what a lot of racers do: Make chalk marks across the
tread and extending a little way up the sidewall. Drive around the
block, then look and see where the chalk mark is rubbed off in relation
to the edge of the tread. If the chalk ends right at the edge of the
tread, you're at the right inflation level. Drastic over or
underinflation will show up as wear past the edge of the tread, or even
an unworn stripe in the middle of the tread. Do it a few times with the
pressure intentionally high and low, to see the effect on your
particular tires.

It sounds a lot like you have alloy wheels and the wheels are leaking.
Why people want those things that cost more and function less is beyond me.

--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math


"Jonny" <spamyourself (AT) blackworm (DOT) net> wrote

On Wed, 25 Oct 2006 23:40:23 GMT, "Joseph Meehan"
<sligojoeSPAM (AT) hotmail (DOT) com> wrote:

Did I miss something? I have not experienced tire pressure loss any
faster on my cars with alloy wheels than I have on my lawn mower,
tractor or truck with steel wheels.

Alloy wheels leak always. Especially if it snows and the city puts rocksalt
down. Across all brands. I could call 5 guys right now with leaking alloys.
they leak at the bead by the balance weights from corrosion.
"Jim Behning" <jimbehning (AT) doesthisblockpork (DOT) mindspring.com> wrote