L. Long

Please bare with me all, can some tell me if you can put the z51 rims on a 2Lt. I asked the question to my salesman and he said GM said you couldn't, but they didn't give him an explanation.

Gr8ful

I think he wrong.

Tulsaeasyrider

I have a Z51 wheels on my C7 2LT.

Fugitive C7

isn't 2lt an interior option? Regardless, z51 rims bolt directly to non-z51 cars without a problem.

MisterMe

OK. My GM dealer fills all tires with nitrogen, not just Corvette tires. The justification in the literature for the nitrogen tire filler is that nitrogen gas has a larger molecule than the oxygen molecule that composes 20% of air. The rest of air is about 80% nitrogen plus other trace molecules. This is all true. You should have learned this in your high school chemistry and physics classes.

The larger molecule of nitrogen is supposed to be much less likely than the smaller oxygen molecule to leak through the rubber of the tires. My experience does not bear this out. When filled with nitrogen, my tire appear to lose pressure faster than they do when filled with air. For this, I have neither an explanation nor even a hypothesis.

Even if there is an unaccounted mechanism that is facilitating the leaking of nitrogen, it still has theoretical advantages over compressed air. Nitrogen gas has a lower effective molecular weight than air--28 grams (N2) vs. 28.8 grams (air). Thus nitrogen-filled tires have a slight unsprung weight advantage over air-filled tires.

Another of the advertised advantages of nitrogen over air is that nitrogen gas is naturally dry. Compressed air is measurably humid. If you don't need water, then you don't want water. Another tiny advantage of nitrogen gas.

Compressed air is 20% oxygen. Oxygen oxidizes the rubber and other carbon compounds in the interior of your tires. This a very slight effect, but it has no upside. Nitrogen gas is effectively oxygen-free and, thus, cannot oxidize anything. Nitrogen is not chemically inert, but nitrogen gas is effectively inert for most practical purposes. It does not react.

The bottomline is that you should follow your Operators Manual. The Manual is mute on your tire fill gas. For racing, nitrogen has definite advantages. Otherwise, accept nitrogen if it is offered. If it is not offered, then don't worry about it.

Tom Hewitt

Nitrogen is a compressible gas and obeys Boyle's P,V,T relationship just like any other gas. It is inert, meaning it generally does not react with other chemicals at normal temps, and is therefore a little less likely to degrade the internals of the tire which includes the sensors and run-flats.

Sorry…but correct info is important.

PS: My new Z51 C7 has green caps for whatever that's worth.

Tulsaeasyrider

Purchased through South Point. Do you know the tires don't have nitrogen, or, maybe, they just didn't announce it?

carczar

Nitrogen does NOT expand and contract, It is also used in automatic altitude compensators to adjust the fuel air mixtures in aircraft carbs. The reason this works is the air is thinner at altitude and changes the position of the needle valve in the AATC.. Trust me Nitrogen done NOT expand and contract.. I am a retired Master Chief Aircraft Mechanic, I worked on these engines for 20 years and know how they work.

My LMR C-7 just made 844 RWHP today, can't wait to get my hande on this beast......

LT1xL82

Firstly, thank you for your service.

Secondly, you have this one all wrong Sarge. In fact, your example illustrates that nitrogen does indeed expand. With the air pressure lower at altitude, the constant number of nitrogen molecules within the compensator EXPANDS until it's pressure equals that of the outside air. That's what is moving the needle.

The most likely reason nitrogen is used in the compensator is it is dry, and hence there is no water vapor to freeze in the cold, high altitude environment.

carczar

Sorry to disagree, Its the atmosphere that makes the needle go up and down pushing on a bellows filled w/ an inert gas (Nitrogen) So let me give you another example. I flew Helicopters and the Oleo strut on the side w/ the engine exhaust would be 6 inches higher after a flight when the hot exhaust gas blew on it for an hour or two, but when we started using Nitrogen they never moved a inch. so how would you explain
that ?

LT1xL82

plasticzar, you believe nitrogen does not expand and contract. I believe it does...closely approximating PV=nRT.

To keep things simple and friendly, let's agree to disagree.

We both have a passion the plastic fantastic, so what else could possible matter?

carczar

Hope this answeres your question, Jay Leno explains:

http://www.getnitrogen.org/

MisterMe

This is not something that you can agree to disagree about because it is not a subject that is open to debate. The Ideal Gas Law, PV = nRT, is a basic law of physics and is taught in every first semester college physics and chemistry course. It is also taught in high school physics and chemistry courses.

At the temperatures and pressures inside automobile tires and aircraft compensators, nitrogen obeys the ideal gas law. First, an explanation of terms:

P. This is the absolute pressure. The absolute pressure in a tire is Pg, the pressure as measured by a tire gauge, plus Pa, the atmospheric pressure as measured by a barometer. Atmospheric pressure is also known as barometric pressure. Barometric pressure is about 14.7 psi or 101.3 kPa.

A flat tire has pressure 14.7 psi inside. It is flat because the ambient pressure outside is also 14.7 psi. A tire [or anything else] can be inflated only if it can support higher pressure inside than outside.

Each tire supports an amount of weight equal to the tire's gauge pressure Pg times the area of its contact patch.

V. This the capacity of the sealed container. The fill gas completely occupies this capacity. In the case of a highly elastic container like a toy balloon, the container expands in almost direct proportion to the amount of gas in the balloon. In the case of a less elastic container like an automobile tire, the container will expand as fill gas is added but it will not expand much. The behavior is essentially the same whether you use nitrogen or air.

n. This is the number of moles of fill gas. In the case of nitrogen, a mole is 28 grams. Because air is a mixture of gases, the term does not apply. However, 28.8 grams of air are effectively one mole of the mixture. One of the trace gases in air is water vapor. In my experience, compressed air has a larger fraction of water vapor than ambient air. In fact, I often get a small amount of liquid water in my stream of compressed air.

R. This is the Ideal Gas Constant. It plays no rule in the fundamental physics. It ensures that all measured values have consistent units.

T. This the absolute temperature of the gas inside the container. As measured by a Celsius thermometer, water freezes at 0 °C. However, the SI absolute temperature is measured in kelvins. As measured by a Kelvin thermometer, water freezes at 273 K. To determine the absolute temperature T, add 273 to the Celsius temperature.

The Ideal Gas Law tells us that absolute pressure is directly proportional to absolute temperature for a fixed-capacity container. This is why tire pressure decreases in cold weather.

In an earlier post in this thread, I discussed the differences between nitrogen and air. One difference that I did not discuss is the liquid water that is often part of the stream of compressed air used to fill tires. Because water undergoes phase changes at the temperatures of interest here, it may not obey the Ideal Gas Law.

When water evaporates, its volume increases by a factor of about 1000. When it freezes, solid ice may form inside your tire. If any of the water in the tire is liquid, then it contains living microorganisms.

We cannot forget that 20% of air is oxygen. The combination of oxygen and water inside your tires in not good. That said, the damage done by this combination may well be negligible for the life of your tires. If this is the case, then filling your tires with nitrogen may not be economic. Economics aside, there is no upside to filling your tires with air instead of nitrogen. If nitrogen refills are free or available at the same price as air, then refill your tires with nitrogen.

LT1xL82

It's called graciously bowing out. I had/have no deep seated need to beat an issue to death simply to try and prove myself correct on an internet forum.

For whatever it is worth, I TOTALLY agree the technical information you shared in this post.

carczar

Agree everyone, let's put this to bed, I think we all agree Nitrogen is good for your tires.. Enough said..

LT1xL82

Stinker Toy

There is actually a benefit to nitrogen that was not mentioned here that I could find.

Nitrogen-filled tires leak less over time. That's because nitrogen molecules are more hot-dog shaped than oxygen and about 3 times larger. That means they leak out less over time. Admittedly, there's only 22% oxygen in a tire anyway, but for the masses, keeping tires properly inflated longer is an energy saver and a tire saver.

Most people won't check their pressures every month or so, and this will help. That's probably the biggest reason the industry is going that way.

MisterMe

The benefit that you could not find is in the first line of Post #25 of this thread. Lest there be any confusion, reduced pressure loss due to fact that elemental nitrogen has a larger molecule than elemental oxygen is a major advertising point for nitrogen-fill systems.

I went through the qualities of nitrogen vs. air in Post #25 and Post #33. The point that I was making is that nitrogen has advantages over air, but its advantages are subtle. Subtle advantages may be swamped by other issues that you can't account for. My own experience using a nitrogen fill from my dealer was that my tires lost pressure faster than with compressed air.

My dealer is the only place that I know in town that has a nitrogen fill system. The advantages of nitrogen are not dramatic enough for me to go back to my dealer every time my tire pressure needs to be checked. I refilled with air at a convenience store on the way to work. If I had owned a nitrogen refill system at home, then I would have used it. If the convenience store supplied nitrogen along side air, then I would have chosen nitrogen.