Nitrogen in tires?

There was a recent post regarding this subject. Nitrogen is used in high performance applications like in some race cars and aircraft because it contains less moisture than ambient air and so there is less pressure differentiation and corrosion; the nitrogen itself causes less pressure differentials due to temperature, and it supposedly leaks more slowly. As a practical matter, there is probably little difference between ambient air and nitrogen for passenger car tires, especially if the ambient air is run through a drier before being discharged from the compressor. Bottom line, save your money.

In automotive applications it makes a lot of profit for the seller.

Ray:

A friend of mine fell for this scam at a Cosco store recently, because they told him the big advantage of nitrogen was that it did not expand like air when it got hot, so the air pressure in his tires would stay stable.

The more I thought about this the worse it sounded. Car manufacturers recommend a specific cold PSI number for their tires, knowing that they are going to heat up under normal driving conditions. If you use nitrogen, then aren't you essentially driving on underinflated tires all the time?

The last 3 cars I've owned (1997 ES 300, 1987 Acura Legend Coupe and 1983 Pontiac Firebird) all suffered from slow tire leaks after about 3 to 5 years. I repeatedly had to get the rims sanded to stop these leaks, but in all cases, I was told that eventually the rims would have to be replaced. In fact, the prospect of replacing the rims probably motivated me to sell these cars sooner than I would have otherwise.

I live in the snowbelt and, on these 3 cars, I religiously kept the tires filled with air at 32/33 PSI. Also, I keep my cars for 5 to 10 years. I wonder if this frequent checking/filling introduced moisture which accelrated rim corrosion.

Where do you find that? I don't know anywhere that's available.

On my current car (2004 ES 330), I rarely check/fill the tires. From past experience, I figure that the more often you fill them (with regular "moist" air) the more often you'll have to fill them, due to accelerated rim corrosion.

Good point. The answer is probably, yes, unless whoever is filling the tires knows to increase the pressure. I am a believer in adding 4 to 6 PSI to the automaker's recommended cold tire pressure to even out tire wear. I've found that the outside tread will wear more quickly using the automaker's recommended tire pressure, and adding the 4 to 6 PSI evens tread wear, at the cost of a slightly harsher ride.

I do the same thing, for the same reasons. I don't really feel that the ride is that much harder. Four extra PSI on the right, five extra PSI on the left. (I enjoy my beer and BBQ, and I carry the results with me every where I go!)

Sanding the rims exposes bare metal to moisture, so a clear coat of lacquer should be applied after sanding, or the problem will continue to appear. Cast alloy wheels are porous and so the wheel manufacturer paints the inside surface of the wheel with a clear coating which is removed when sanding.

Possibly, especially if you fill from a compressor with a tank.

Many, but not all, dealer service facilities use a drier on compressor discharge air. My unscientific wild guess is that driers are less common at at quick lube and independent service facilities. Basically, a drier chilles the air so that moisture condenses out like a de-humidifier. Removing the moisture from the air will prolong air tool life, and a side benefit is that it will reduce the amount of moisture introduced into tires. Moisture will condense in the bottom of compressor tanks, and the tanks should be drained daily to reduce the amount of moisture in the discharge air. I'll admit that I only drain the tank on my compressor two or three times a year, when I notice moisture coming from the exhaust ports on my air tools. I have a moisture separator/filter on my home compressor but it does not do an effective job at removing moisture.

My guess is that those inexpensive tire pumps that plug into 12 volt or 110 volt outlets introduce less moisture into tires than a compressor does because it is not holding a large volume of air. Those pumps take a long time, so I just use my compressor.

The next time you have a leak due to a porous alloy wheel or corrosion on the wheel rim, have the service facility paint the corroded areas, the places they sanded, and the entire rim with a generous coating of bead sealer before installing the tire. The black goop does a pretty good job of slowing down re-occurrences.

Yeah, that's what most gas stations have. I used to fill my tires at gas stations all the time. Not anymore.

I asked one of the service reps at my Lexus dealer and he didn't even know what I was talking about. They may have a drier on their compressor, but the rep doesn't know about it. But then, who knows when was the last time they drained the unit?

I have one of those in my trunk. It's very slow. I should have paid another $10 or $20 and gotten the faster one.

I've always had my rims sanded at a name brand tire dealer and they've always put on the black goop for sealing. Nonetheless, that stuff only lasts a year or 2 if I'm lucky.

Most Lexus dealers have very nice facilities and equipment, so I would imagine that they have a drier installed on their compressor. They may even have an automatic tank drain. The service manager would know what type of equipment they have and who is responsible for maintenance, probobably the team leader or shop foreman.

I've been thinking about getting one for long trips but have never gotten around to it.

I did not have success until I got them to coat the entire interior of the wheel with the bead sealer, and that worked for the life of the tire.