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Originally Posted by barcalad Now, since you brought this up, I'll ask your opinion about this. While getting the N2 thing done today, I asked the Manager that if I'm on a road trip, and if I feel that I should increase/decrease the pressure, can I go for normal air if I don't find any N2 stations? He was like 'Yeah. You can do that. Not a problem'. However, I'm not quite convinced with this theory of mixing up N2 and Normal Air in tires as expensive as these. What would be your opinion on this? |
As man_of_steel mentioned, normal air is 78% Nitrogen, 21% Oxygen and rest are other gases and moisture. So topping an N2 tyre with normal air (in case if you don't find any N2 stations) does not make much diff in the short run. before that let me put forward something.
Nitrogen is an inert, non combustible and non corrosive gas. compared to this oxygen is corrosive (oxidation), aids combustion and is relatively unfavorable with regard to the rubber (read tube and tyre).
Oxygen (read normal air) permeates through the rubber pores. that is why our tyres tend to lose pressure when not used or generally over a period of time. Nitrogen on the other hand does not permeate through rubber and so a tyre filled with nitrogen will hold the pressure for a longer duration in comparo with normal air filled tyres.
Humidity (moisture) is a big culprit here. Normal air contains humidity (moisture) more so with salt content in our coastal areas. so when you put normal air in your tyre you are essentially putting some moisture / water vapor in your tube. Now with increased temperature water vaporizes or condenses and this directly effects your tyre pressure ( tyre pressure increases with temperature, though not extremely but still to the effect that your tyre pressure is different from what you wanted it to be). then water vapor comes in contact with metal and corrodes the same too ( ever wonder when you take a tyre to puncture shop, you see corrosion in the edges / inside of the rim?) so moisture with oxygen corrodes / permeates and this leads to reduced life of the rubber ( remember how a rubber band left unattended after a few months becomes placid and sticky and loses its elasticity). Now nitrogen filling means dry nitrogen and it does not have any moisture in it. so all the ill effects mentioned above are taken care of. further Nitrogen molecules are larger than oxygen molecules and hence does not permeate through rubber which essentially means that once your tyre has a certain pressure, it remains the same over a long period of time and also over an temperature increases ( during long rides or hot days)
So when nitrogen is filled in a tyre for the first time, the normal air inside is purged many times so that only pure and dry nitrogen replaces the space in the tube ( else the whole exercise is wasted right?) and if you top up nitrogen with normal air your tyre now has oxygen, perhaps some moisture and nitrogen and you are back to square one.
So if you are sticking with nitrogen it is great, but mixing with normal air (though it does not make any immediate impact) in the long run it is as good as running normal air as temperature changes, pressure changes, corrosion etc keep occurring.
In racing Nitrogen is used because for them tyre pressure is extremely important and the tyres get up to very high temperature and even slight change in pressure could mean win or loose situation for them.
Ride quality wise it does not make any difference as technically when you are riding, the compressed air in the tyre takes the load and hence should not matter though ride under constant pressure tyre is better than a varying pressure tyre. but with nitrogen filled the life of the tyre increases as normal air tends to reduce the life of the rubber and as nitrogen is inert gas, the tyres run cooler than normal air filled tyres.
For all the positives, the drawback lies in finding nitrogen filling station every time you need it, when ever and where ever you need it and then pay for it every time and then some day you put normal air you got to start all over by purging the whole gas out and refill it with pure nitrogen and the cycle starts. that means maintainability, availability and cost goes against the benefits.
I on the other hand check the air pressure every time I fill petrol. I tank her up fully always and most of the time the tyre pressure is same or a tad lesser. so that works for me.
Hope that helps.
