I just had a discussion with a friend who has his car tires filled with Nitrogen. He swears by it and told me that recently he experimented with nitrogen on his road bike and he said he can tell a difference as the tires seem to stay inflated to the proper pressure longer and rarely requires adjustments.

I work in the car industry and I'm very well aware of the alleged advantages of filling car tires with Nitrogen but I'm not 100% sold.

Please discuss your opinions/experiences with road bike tires filled with Nitrogen.

When I was racing motorcycles, this idea was widely promoted as well, as a way to maintain consistent pressure and performance. To be quite honest I never noticed a difference, even while racing in all kinds of conditions for different lengths of time between 8-lap sprints and 8-hour endurance races. I guess when you're absolutely at the razor's edge and that very small difference might turn into a winning advantage, maybe it is worth the trouble. It really wasn't for me or any of my teammates.

Normal air is already 79% Nitrogen anyway, so you're just removing the 21% variable of Oxygen and other trace gases.

I think nitrogen is good for inflating bike tires but I'm not 100% sold. More like 78%.

Nitrogen? Again? Can't you smell BS when you get that close to it?

How about helium or hydrogen to decrease weight? And it's rotating weight too!

The permeability of oxygen through butyl rubber is about 11% higher than that of nitrogen. Oxygen is about 20% of the air we breathe. So air filled tires will deflate at about 2% faster rate than nitrogen filled tires. The moisture in air effect on pressure changes with temperature might be significant, but really, the whole thing is a lot of nothing.

For car or motorcycle racing where the tires are likely to experience considerable temperature variations the main difference is that you eliminate the variable amounts of water vapor that are present in regular air. As the tire temperature changes the water may sometimes condense out as a liquid and other times be present as a gas and thereby contribute to an increased tire pressure.

And yes, N2 is slightly less likely to diffuse through the rubber walls of the tube than O2 - but I find that the tire pressure in my 23mm road bike tires stays uniform enough as long as I check it every week or two and in my 35mm touring bike tires it's sufficient to check every month or two so I'm not motivated to switch to pure nitrogen.

Check and fill your bike tires every ride. Easy-peasey. No worries. No pinch flats. No discomfort due to overinflating to combat pressure losses. Just better all around.

Totally useless for bike tires. The main advantage of Nitrogen for cars is that its a dry gas which contains no moisture. Moisture can cause corrosion, which is a very minor issue.
The bigger issue is that the water condenses out when the tires are cold, but once they heat up it evaporates resulting in large tire pressure swings. Bike tires don't really get hot, other than long descents with heavy braking, and even then are still much cooler than car tires. The operating temperature of a race tire is 200F, your bike tire never gets that hot.

Using Nitrogen for car tires is just wasting money unless you happen to own a shop with free and unlimited access.

Car tires run tubeless, should we do that too? Maybe tubeless AND nitrogen.

The biggest advantage to nitrogen in tires, especially auto tires is that it comes from a bottle, and therefore is 100% dry (no water vapor). Compressed air OTOH, is rarely as dry even with line driers.

Most of us have very nitrogen rich air in our bike tires anyway, simply because the oxygen bleeds out faster. So the first time we pump the tires we start with the normal 79/21% ratio. When we've lost a few Psi, the oxygen will be disproportionately lost, so after we top off the ratio will change to (arbitrarily) something like 85/15%, and eventually if we keep topping off at 10psi short, the ratio will be something near 98/2% with the only oxygen being from the 10% of new air.

Once it reaches that ratio it's stay there forever, unless you replace all the air and start fresh.

BTW - the number of pump cycles to reach near pure nitrogen varies with the difference in oxygen vs. nitrogen loss. So, ironically there's a catch-22 here. The greater the case for using nitrogen to reduce air loss, the fewer cycles needed to reach the nearly pure nitrogen state. Next time someone suggests pumping with nitrogen, tell them that you don't bother because nature provides so well.

Does the gas actually go around?

Absolutely. Why wouldn't it.

If you want to be absolutely accurate, there's be a short lag as the tire spins and the air doesn't, but friction inside will have it turning with the tire in very short order.

You can see the same effect in a spinning vessel full of water. Initially the vessel spins and the water sits there, but it begins to spin at the sides, then soon is spinning with the vessel. If the vessel stops, the water will continue spinning a while until friction slows it.

Gas is fluid!

I need a Bluetooth or Ant+ tire pressure monitor system to go along with my nitrogen-filled bike tires. That should boost me to the top of the Hot-r-not dogpile.

I had a car with the "Nitrogen Option" -- what a joke. Every time a tire was low you had to take it in to have it filled. Never again! Like PT Barnum said: "There's a sucker born every whatever". This goes double for bike tires.

Actually the higher the viscosity of the fluid, the more effectively it rotates with the tire. A very low viscosity fluid like a gas will rotate with the tire nearly completely near the wall of the tire and hardly at all in the center of the chamber.

Let's think about this logically.

If nitrogen filters through inner tube walls slower than other gases, then that 78% nitrogen ratio will slowly increase over time as you re-fill your tubes with new air.

After x number of fills, it will be almost pure nitrogen.

Therefore, if what your friend is saying is true, then the best course of action is to DO NOTHING.

edit - what FBinNY said.

Logically that's not true. Filling a tire with a pump continues to add water vapor. Pure nitrogen from a tank is dry.

You may also collect water in your tube with repeated refilling of not-so-dry air.

Some people seem to like CO[SUB]2[/SUB] (which I think has a higher permeability, and is also a heavier gas than O[SUB]2[/SUB]/N[SUB]2[/SUB]). But, the differences are so minimal that I wouldn't worry about it either way. Your bike tires don't generate the heat that car tires may generate.

I'm not too concerned with pressure. Periodically I do a thumb test, and add more air as needed, usually less than once a month or so. I don't think I very frequently get above 80 psi, so I may be a little lower than average here for 23/25mm tires.

I think the biggest advantage of Nitrogen is that it is usually a dry air supply. You should be able to dry compressor supplied air reasonably well.

^^ Any problems with pinch flats using this strategy?

I had one pinch flat last year (about 2000 miles on my road bike) when I hit a stick on a rapid descent on my driveway (30+ mph). My summer was flat-free except for the one pinch flat. This fall & winter I've picked up wire, and a couple of pieces of glass.

I know I've had the occasional snake-bite flats in the past, but hadn't really realized the cause.

I tend to try to avoid hitting big bumpy stuff, and slow down for things like rough RR crossings. But, I have also hit some road debris on the shoulders without flats.

I did try to put in about 100 PSI in my tires a couple of times this year, but didn't really like the extra bumpy feeling (perhaps a sign I should be riding bigger tires, but I still like my small tires).

Not me, but I've seen clips of wicked single-bike corner crashes in races that I don't think should have happened. It appears as if the bikes just slide out from under the riders. I do wonder if some riders are using too high of pressure.

It's a hoax.

Good review re car tires:
1) very little difference and no practical difference
2) Costco gives free nitrogen for inflating tires

Should You Fill Your Car's Tires With Nitrogen?

Actually, I use a specially blended inflation gas mixture - it has 78% nitrogen, 21% oxygen, and 1% secret ingredients. Makes my bike go really, really,fast when it's pumped in to the correct pressure. If you want to know where to get it, PM me with your check for a $100.