hey guys,

i recently had my tires filled with nitrogen, however i just noticed that my front wheel is a little low and it really bothers me.


the place that filled my wheels is really far away and i cant get there for at least another 2 weeks.

is it safe to add a little regular air to my tires and mix it with the nitro.

 

yes. air is 79% nitrogen.

 

STAND BACK - IT'S GONNA BLOW!!!

Kidding, of course. It won't hurt anything at all - you're just diluting your 100% nitrogen slightly with a blend of 78% nitrogen/22% oxygen.

 

oh cool so nitrogen is thnat effective huh

is it gonna weight my wheel down or something lol

 

What advantage is there to using pure Nitrogen in your tires? being pure does it make it more prone to slow leaks??

My friend thats into Jeep's and 4wheelin said they use Co2 for their tires due to the tanks being small and easy to haul out on the trails.

 

There are several theoretical advantages to using nitrogen in tires:

- contains less moisture, so pressures stay more constant with heat cycles (that's why racers user it)
- completely inert gas, so less corrosion of wheels and oxidization of rubber (that's why truck fleets use it)
- less pressure loss since larger nitrogen molecules don't migrate through the rubber as easily as oxygen molecules (questionable, IMO)

You'll hear stuff like "lighter/heavier", "better handling" or "fire resistant" mentioned, but these are just stupid.

In actual practice, street cars don't heat tires up enough, or keep tires long enough to get any real benefit. On the other hand, it won't do any harm either.

 

Nitrogen filled tires will not have tire pressure vary due to outside temps. Therefore there should be no need to fill the tires as the weather gets colder, etc. I've also read that it is better for the rubber (doesn't dry it out as fast I think). Then again, by the time this happens, more wear from day to day use has made it ready to replace anyways.

 

But the way our g eat tires you will never see any of these benefits

 

Sure, you can add air, but slowly it will defeat the advantages of the nitrogen. But if you add say 1 or 2psi a month I don't think it's a biggee.
The number one advantage is less moisture. If you have a small and clean 3 or 4 gallon compressor at home and purge it before and after to keep the tank dry, you could accomplish almost the same thing IMO. If you have a large compressor at home, make sure it has a filter and drier, especially if you use it with power tools.
It's the huge tanks in self-service stations that collect moisture over time that are probably the biggest problem, as are their inaccurate gauges.

 

its going to leak just not as fast through the valve stem and around the beading...i have nitrogen in all my cars, only cause it was free, and i still have to go back when i get oil changes done to have it retopped

 

Not true, all gasses including nitrogen expand and contract with temperature, gotta remember air is mostly nitrogen to start with. Its nothing magical, still has to follow the laws of physics

 

^^^Then why do professional racers make 1/4 to 1/2 pound changes in their tire pressure for on going changing track conditions and handling improvements?
If nitrogen expands with heat, then whats the point of those small pressure changes? Racers would have no control over their tire pressure/handling characteristics.
Not an expert, but that's my logic and what I've heard in the past.

 

I think the point of nitrogen was that the expansion and contraction of the molecules is smaller than oxygen. Therefore, when you're pumping in regular atmospheric air, you have the oxygen aspect which is a bigger factor. When you pump in pure nitrogen, you are eliminating that. Saying that nitrogen doesn't expand or contract at all is not accurate. It's just less, hence the benefits. Will the common day to day commuter really feel a difference? Probably not.

 

Got this off of a site where a bunch of engineers beat this topic to death. This was the best summation.

http://www.eng-tips.com/viewthread.c...=120996&page=1

John


1. Air is 78% nitrogen, N2, and 21% oxygen, O2. So even if you put air in the tire, it's already 78% nitrogen. Many of the so called nitrogen generators don't produce much more than 90% nitrogen.

2. At relatively low pressures (ie tire pressures) N2, O2 and water vapor will all behave as ideal gases, and follow PV=nRT. Pressure will increase or decrease to the same extent as the temperature increases or decreases regardless of which gas is in the tire. (Even at 300 psi, which is about 20 atm, there is little deviation from ideality.) Therefore the comments about N2 not changing in pressure as the temperature changes are without merit.

3. The rate of effusion (or diffusion) of a gas through a porous membrane depends on the molar mass and to some degree on the molecular diameter. N2 and O2 are almost the same size and N2 is lighter than O2 (28 g/mol vs 32 g/mol) so if either gas were to effuse out of the tire, nitrogen would do it more quickly.

Every gas is going to escape from a tire, regardless, as long as the pressure inside the tire is greater than the pressure outside the tire. The gas molecules are going to diffuse through the walls of the tire at a very slow rate. It doesn’t make any difference what the gas is, although there are small differences between the diffusion rates of oxygen and nitrogen. Since nitrogen is slightly less massive than oxygen (28 g/mol vs 32 g/mol) Graham’s law predicts that nitrogen will diffuse slightly more rapidly than oxygen.

Luckily, tires are designed not to be porous membranes.

4. N2 and O2 both have essentially the same specific heat capacity, about 1.0 J/gK, and thermal conductivity, about 0.00026 W/cmK. Water vapor has a specific heat capacity of about 2 J/gK. But remember, water vapor will constitute less than 1% of the air in the tire. So the idea that N2 has different heat handling properties is also without merit.

5. The ozone, O3, in the atmosphere, which is a ground level pollutant, will do a great deal more damage to your tires than the O2 inside the tire.

Several have suggested that N2 in a high pressure tank is more portable and requires no electricity. That would make sense, particularly for aircraft tires.

I find no reason to believe that N2 is going to produce a "better ride" or "better handling".

The bottom line is that for general passenger car tires or truck tires there is nothing to be gained (other than portability) by using nitrogen rather than air. The biggest gain will be $$$ by the companies that sell nitrogen handling equipment and the tire merchants that appeal to ignorant customers. And who is the biggest loser?

Yep, the consumer.

 

Redlude97 is right, nitrogen still expands with heat. The reason racing teams use nitrogen is that, having less moisture than regular air, the pressure swing is less during extreme heat cycles, and the expansion is more constant. They can better predict the cold pressure required to get the specific hot pressure they want.

Street tires (in street use) don't generally go through those same extreme heat cycles. Even if they did, I'm sure you'd be at or past the limits of so many other components of the car that the effect of tire pressure change would be impossible to feel or measure.