Gas station compressed air

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?

Reply to
TL
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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

Reply to
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.

Reply to
Chasqui

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!

Reply to
4Motion

Water seperators for compressed air systems are to protect the tools. The amount of moisture getting pushed in a tire on a super humid day would not cause any problem for the tire, and would not effect the tire's performance.

However, if you really wanna screw with someone, take the valve core out of a front tire, then put 1 quart of water into the tire though the valve stem, replace valve core and reinflate the tire. When the mark drives straight, the water will even out and no vibration, however when the mark turns, the water will slosh to one side and cause a hell of a vibration. Did this to my step brother years back when we both worked at a tire shop, he didn't find it as funny as everyone else.

Reply to
Pencilneck

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

Reply to
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" wrote:

Jim B.

Reply to
jimbehning

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.

Reply to
Bob Hetzel

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