I've heard two excuses for Nitrogen in tyres, first one was for racing cars because its lighter and doesn't attract moisture , and the second was even better in that the molecules were bigger and less likely to leak out of the valve and tyre both of which mean nothing in the real world. Air is suprisingly good for the job and if you are lucky it's free :thumb:
air is about 70% nitrogen, if the tire place will do it free, go ahead. The big benefit is it has no moisture in it, so it won't rot the tire from the inside (is that really an issue these days???) the big benefit for race-cars is the moisture in non-dry air will boil and increase the tire-pressure, causing problems. It's easier/cheaper to cary bottles of N2 to the track than a compressor with an efficient dryer assembly.