Originally Posted by
Sydneykid
From someone who has been using nitrogen in race car tyres for 20 + years I can confidently say that, all other things being equal, there is no way a race driver, even the best ones, could feel the difference between 78% nitrogen and 100% nitrogen. The reason why we use it in race car tyres is the expansion rate of 100% nitrogen is less than air. As the race tyre heats up the pressure grows, with 100% nitrogen we don't have to have as big a gap between cold and hot tyre pressures. This means the car is faster at the beginning of a race because the tyres are closer to their ideal pressure. And/or the car is faster at the end of a race because the tyres haven't over pressured.
I would add that on humid day or when using an air compressor with poor water filtration the effect of tyre temperature on tyre pressure growth is much greater. So we get more of an advantage out of using 100% nitrogen, because it has zero humidity.
As for purging the air, filling, emptying and refilling the tyres a couple of times with 100%nitrogen does a good enough job of removing the 22% of other gases. I have tried using a vacuum pump instead of multiple fills and the difference in tyre pressure is not noticeable. Even on days at 40+ degree air temp and 65+ degrees track temp.
Cheers
Gary