Another post here about keeping tires inflated, reminded me of a
question I've been wondering about. When I had a shop many years ago,
our compressor had specific provisions to get freed up water vapor out
of the compressed air. I look at those little electric air compressors
at gas stations, and wonder about that water vapor. I've found if I
use my gauge torelease a blast of air from the hose after the
compressor starts up, I get a small cloud of vapor that otherwise
would have gone in my tire. I can't believe adding water / humidity to
ones tires is a good thing.

Anyone have any info on this?

TL <tlehman (AT) visi (DOT) com> wrote

Never heard anything about this, so it can't be an issue. The rubber
is designed to withstand salt water and other contamination on the
outside, so it should be able to tolerate a little condensation on the
inside. The main issues affecting the rubber are UV light, certain
chemicals, and age.
H2Only

When you let out the blast of air from the hose, the air comes out cold. It
is a result of the pressure change. This drop in temperature makes the water
vapour in the atmosphere condense. There may not have been water vapour in
the compressed air. When you pump that directly into your tire, you don't
get the water vapour from the atmosphere.

"TL" <tlehman (AT) visi (DOT) com> wrote

I've never had any problem with this that I've noticed, but I think I read
somewhere that there is a danger that the water vapor could turn into steam
in a hot tire and cause damage (rupture?). I cannot remember where I read
that, but I do remember that wherever it was, there was no evidence that it
had ever happened to anyone.

I wonder if that vapor could freeze in your tires in winter? What would
*that* do? Yikes!


"TL" <tlehman (AT) visi (DOT) com> wrote

"TL" <tlehman (AT) visi (DOT) com> wrote


This is a pretty simple one. The best thing to inflate your tires with is a
fairly stable dry gas, for example nitrogen.
Failing that you want dry air.
Water vapor in the tires expands much more with temperature variation than
does dry air, thus causing your tire pressure to be much les stable over the
course of driving. More stable tire pressure (if it is the correct pressure)
reduces tire wear, increases gas mileage, and provides predictable handling.

Not usually much of an issue on a street car at normal highway speeds with
the little bit of vapor the gas air pump puts in.
Very important in a race car at the track.

Scott

I would disagree with that statement. Drain the water out of the
little tank on the compressor and try the test again. I bet there is
little or no condensation. I have drained what seems like gallons of
water out of various air compressor tanks. Some of that water does
come out of the air hose.


"Chasqui" <chasqui (AT) comcast (DOT) net> wrote:


Jim B.

The problem I'm referring to is actual water. Water gets in a gas station air
compressor a variety of ways... here's the top two that come to my mind...

1) it condenses on the air intake at night, as the intake for the air
compressor sucks, it brings some of the water in with it...

2) always present in the air as vapor, when you increase the pressure of the
air the moisture changes phase from a gas to a liquid and then condenses in
the bottom of the tank.

Water vapor in your tires is not a problem at all. If it hasn't condensed at
35 PSI it's not a problem. Most people don't drive in a way that gets the
air in their tires so hot the pressure is raised up a lot (i.e. more than
10 PSI).

Water vapor doesn't expand with temperature different than any other gas,
unless you cool it enough to make it change phase back to liquid water.

Also, another poster suggested water in a tire may boil. This is crazy.
You'd have a much bigger problem to worry about if your tires were getting
hot enough under that kind of pressure for the water to boil. Even your
radiator doesn't get that hot and it's only at 12-15 PSI for most cars.