You’ve probably heard that you can have nitrogen pumped into your tires in a growing number of locations.¬† The theory is that nitrogen molecules are larger than oxygen molecules and are therefore less likely to leak¬†through your permeable rubber tire.¬†¬†Most of us have atmospheric gas (air) in our tires which is made up of 78% nitrogen, 21% oxygen, and 1% other gases.¬† Service stations selling nitrogen for your tires typically¬†fill with¬†a 93% – 98%¬†concentration of nitrogen.
Tires leak in a number of different ways.¬† There could be a hole in the tire made by a foreign object, a poor seat on the rim, a malfunctioning valve stem, or typical permeability¬†through the tire rubber.¬† If your tires are leaking air from any of the first three, get your tires repaired.¬† These types of leaks allow both nitrogen and oxygen to pass.¬† If your tires are leaking through the pore spaces¬†of the rubber, read¬†on to find out how to fill your tires with nitrogen for free.
The price for filling a single tire with nitrogen ranges from $4 to $10 (USD) per tire.¬† If you have a tire that leaks through the tire rubber, don’t pay for a nitrogen fill up.¬† Simply fill with regular air each time.¬†¬†Here’s the secret: Each time¬†air leaks through the rubber, you lose more of the smaller oxygen molecules than the larger nitrogen molecules.¬† When you refill with air, the nitrogen concentration in your tire becomes greater and greater.
Let’s say your tire¬†requires 100,000¬†gas molecules to fill to the proper pressure.¬† (It will be much more than that, but for the sake of simplicity, we’ll stick with this small, round¬†number.)¬† Ignoring the 1% of other gases, we start with 78,000 molecules of nitrogen and 21,000 molecules of oxygen.
According to the Get Nitrogen Institute, oxygen escapes from tires at a rate that is¬†3-4 times faster than nitrogen.¬† For this example, we’ll assume that with every nitrogen molecule escaping your tire, four oxygen molecules are also lost.¬† Therefore, every time¬†you lose 26,250¬†air molecules from your tire, you are left with pure nitrogen.¬† 5,250 nitrogen molecules and 21,000 oxygen molecules escaped, leaving you with¬†72,750 molecules of nitrogen.
When you refill with air you will replace the 26,250 air molecules with 78% nitrogen and 21% oxygen.¬† The gas in your tire will now contain roughly 93.5% nitrogen and 5.5% oxygen.¬† There you have it.¬† With just one refill of air into a leaky tire, you have reached a nitrogen concentration equal to that which service stations sell for $4 to $10 (USD) per tire.¬† Each time you refill with air, more oxygen is purged and the nitrogen concentration becomes even greater.
Agree/disagree with this logic?¬† Let me know.¬† Curious about helium or hydrogen in your tires?¬† How about glowing neon in your tires?¬† Follow this discussion at MTBReview.com.