Using nitrogen in your vehicle's tires instead of regular air is a not-so-secret performance trick known in NASCAR garages. In fact, you may have seen signs at your local bike shop or dealership lately touting the advantages of running nitrogen.

      We saw such a sign at Cherokee County Cycles in Andrews, North Carolina, and asked proprietor Mike Pike to explain. According to Mike, ambient air typically contains moisture and impurities, making it unstable because it's susceptible to temperature changes. When air is compressed inside your bike's tires they'll expand and contract accordingly. Fluctuating tire pressure also has negative effects on tire life and fuel economy, a legitimate concern as fuel prices rise. Your bike's handling can be detrimentally affected, too.

      Nitrogen, on the other hand, is chemically stable, meaning it keeps tire pressure constant once set, extending both tire life and fuel mileage. Advocates say you'll notice better grip and tracking on the road, too, and when you're riding in the twisties, every bit helps. Adds Mike:

Nitrogen is also a better choice if you're the kind of rider that doesn't check your bike's tire pressure often, because of its stability.

      What are the disadvantages? Well, once you put nitrogen in your bike's tires, you have to maintain its purity to continue enjoying the benefits. Add even a bit of air and you've negated the advantages. But we've noticed that some shops provide free top offs for life of the tire once you switch. Another hindrance is the cost, up to $10 a tire. But proponents feel that longer life and better fuel efficiency offset the upfront cost.

      If you're skeptical of special equipment such as the Nitrogen Generation Systems some of the shops use (the air we breathe is 70% nitrogen, after all,) you might buy bottled nitrogen at your welding supple store and do it yourself, using your own regulator and compressor. The trick is to get all of the moisture out of the tires first. Mike suggests bleeding the cold air, filling the tire about 20% full with nitrogen to absorb any remaining moisture, letting that out, and then filling completely with nitrogen. One benefit of the NGS machine is its ability to vacuum out the air completely before the nitrogen is added. Remember, any bit of ambient air, with its inherent moisture content, will reduce the effects of the nitrogen.

      So let's review: where safety is concerned, nitrogen's stability reduces the damage that water can cause in tubes and valve stems, and it keeps tires properly inflated for better handling. Nitrogen can save money by offering improved fuel mileage and longer tire life, and it's green! Longer tire life means fewer used tires in landfills. Maybe the best time to switch to nitrogen is when you buy your next set of new tires.