[joe_padavano]

http://blogs.consumerreports.org/car...nitrogen-.html

Yes, I'm a card-carrying cyinic, but:

...And while nitrogen will do no harm, manufacturers say that they don't see the need to use nitrogen, which generally adds $5 or more per tire charge."

Also:

We have seen a study by a major vehicle manufacturer which revealed most air pressure loss in tires does not take place through the sidewall of the tire but is due to tire bead to rim bead seat and flange leakage around the valve stem and valve core areas. I dont think any type of gas used would improve pressure loss in these cases.

And finally:

The Rubber Manufacturers Association has also issued this statement:

Applications such as aircraft, mining, and commercial/heavy use utilize nitrogen to help reduce the risk of internal combustion (fire) if the brake/rim/wheel components overheat. Also, dry nitrogen is used in professional racing to help reduce variation in inflation pressures (caused by moisture) where even small differences in pressure can affect vehicle handling at the extreme limits of performance.

For normal tire service applications, nitrogen inflation is not required. However, nitrogen inflation is permissible as its properties may contribute to minor reductions in inflation pressure loss. Nevertheless, several other sources of pressure leaks, such as punctures, tire/rim interface (bead), valve, valve/rim interface, and the wheel, may negate the benefit of nitrogen.

If the tire inflation pressure is below the pressure specified on the vehicle placard, the tire must be re-inflated – whether with air or nitrogen – to the proper inflation pressure.

RMA warns that depending on nitrogen alone to reduce the requirements for inflation maintenance may, in fact, lead to under inflated operation, which may result in premature tire failure.

“With the right amount of inflation pressure, you will achieve optimum tire performance,” RMA wrote. “This means your tires will wear longer, save fuel and help prevent accidents.”

And above all, the RMA bulletin strongly reminded motorists to check tire pressure at least once a month when tires are cold and to use the vehicle manufacturer’s recommended inflation pressure.

“Whether inflated by air or nitrogen, regular inflation pressure maintenance remains critical and necessary,” RMA wrote. “Use of nitrogen alone is not a replacement for regular inflation pressure maintenance.”

The RMA bulletin notes that nitrogen is an inert (non-flammable) gas – basically, nothing more than dry air with oxygen removed (air contains about 78% nitrogen). Because of its inert properties, nitrogen is often used in highly specialized service applications and/or demanding environments.