Inflating tires with nitrogen

Free in the UK where I am. Pressure remains constant for longer due to molecule size compared with compressed air, dry (it has no moisture) so no corrosion inside wheel, less creep of pressure during driving. I have noticed a different "feel" to the car when running nitrogen, I like it. Emergency vehicles in the UK all use it as well as aircraft. It does not accelerate fire in a blow out situation which is why aircraft use it. If you can get it free, why not?

 

I think what you are saying is that by removing condensed water from the inside of a tire, you remove one variable and the inevitable pressure rise will become more of a constant. PV=nRT applies regardless of the gas present (even water vapor) and with constant volume and increased temperature, the pressure has to (and will) rise...how much depends on what temperature the tire started at and what it rises to when up to track temps.

This variable is one that many don't fully consider at the track and points to brake cooling and dissipation of that heat. Lots of heavy braking will heat up wheels and the air inside of the tires contributing to higher pressure than if say running at steady high speed in a straight line.

Brock

 

My old set of wheels and tires had nitrogen in them. New set is just plain air. For street cars I don't think it makes much diff. I'd only fill with nitrogen if it was free. Why pay extra? If I add air at home it's just plain air anyways.

 

While it is overhyped nitrogen is a good choice in tires but I agree with Dave it is usually wasted money on a street car. I happen to have a tank in my hangar since we use it in aircraft tires so I use it since I have it on hand. Do I notice a difference? Nothing other than on my 2010 Camaro which had a slow leak from the factory on the left rear. Nitrogen does not leak out as easily and instead of loosing 5lb in 3 months it has lost nothing.

 

Nitrogen is not overHYPED - it's overPRICED.

Extremely dry air is almost as good as N2, but you RARELY see any tire shop with properly dry air.

The problem is the vapor pressure of water. It adds considerably to the pressure change w/ temperature vs. a dry gas.

If your tire has a cold set pressure of 33, set in a 20C garage, at a 70C temp (high speed, hot roads) a dry-filled tire will gain 5.6 psi, a water-containing tire 9.8 psi.

That's the "extreme" end, but you get my idea.

Dry is good.

To be honest, if I had my choice, I'd fill my tires w/ 50% CO2 + 50% R404A

 

In regards to race tires and racing:
The practical corallary to this is that unless the guy seating your beads of tire on wheel uses anhydrous N2 tank you are going to have this vapor pressure problem because there is no way to get the water out of shop air even if you suck it. The damage is done when the tires are put on. A 55cuft N2 tank costs me $25 bucks to refill. That means it costs me a lot of money to mount my tires (I change tires like underwear at $1400/set from Hoosier). You also can't use soapy water to mount either. Like Dave said you just need to know what your pressure rise will be over a track session and adjust accordingly. In my case on my racecar I get an easy 6 psi increase and I mount my own tires with dry shop air and waterless hairspray or bead sealer. My experiment of N2 mounting of tires and inflation was a painful waste of time. The real problem was trackside if you have to get a tire mounted by the track monkeys they use soapy water and unclean shop air and if all your data is for N2 totally dry you are going to be chasing your tail all weekend. You got to set your car up for the lowest common denominator. As they say sh*t happens and sometimes you got to use trackside support.

 

FBB,

The common practice in switching ANY tire over to ANY gas is a "3x purge" and there are waterless tire lubricants - but the 3x purge takes care of that as well.

Dump, Fill, Dump, Fill, Dump, Fill.

(Dump to 8#, Fill to 3 over)

Usually done by a machine - small ones can be had for $500-$1000 to do it automatically - for the terminally lazy.

Your 55cuft N2 tank starts at 3000psi.

Assuming a tire fill pressure of 33psi, that's 5000cuft of tire fill.

Taking a very much overguessed SWAG of 25cuft per vehicle, one tank will complete the full purge on 60+ vehicles. Nitrogen in tires (DIY) literally costs PENNIES per vehicle. Under $0.50 at your N2 prices.

 

I hear you but not practical in reality realtime. The machine is expensive. I'm so cheap it is hard to justify buying the tire changer when the monkeys can do it for 20 bucks a tire but for me it is about time and quality control. When you seat a bead there is lots of air bleed off before the tire ever starts to inflate and seat. Sometimes you have to wrestle with a bead and you loose even more air. Trackside we are bleeding and adding N2 to tires all weekend long. And then your buddy uses your tank. Your math is right but the realities are there is a lot of waste. I wish my portable 55cu ft tanks would do 60 cars. I use it only on 1 racecar that does have airjacks too and I go through about a bottle every other month! Add that to the synthetic oil changes, gear oil changes, brake flushing, $1400 sets of tires, race gas, track fees and hotels...geez I need a cheaper sport. I have never found a Waterless lube that prevents tires from spinning on the wheel. My data shows easy spikes to 1.5G's. Amazingly cheap hair spray is super slick for mounting stiff race tires yet drys and sticks the tire to the wheel. They do NOT spin period. I race only Hoosier tires. Hoosier has crappy molds and lots of flash on the beads which can cause slow nagging air leaks. When I get a weird tire I mount with bead sealer. It is like rubber cement slippery when wet for easy mounting but sticks when dry and tires do not spin.

 

Nitrogen for tires is a natural for the same morons who pay $100 per foot for exotic speaker wire.
If you really believe that nitrogen for tires is desirable, I'd love to do business with you. Any business, any time. C'mon down, suckers!

 

How about...HYGROGEN!!!! It'll lighten the wheels and if there's a wreck It'll be spectacular!

 

Other benefits:

Improved TPMS Performance – If you have a new car, you likely are plagued by a flashing light telling you your tire pressure is low. For example, one woman's light was going off every four to five weeks. After inflating with nitrogen, her light didn't reappear for 53 weeks!

More Predictable Pressure Fluctuation – NASCAR teams use nitrogen so they can more accurately predict tire pressure fluctuation. Regular compressed air can fluctuate considerably when water vapor is present. Read On...

Longer Rim Life – Rim rust caused by condensation from water vapor and other gases can get caught in valves and create slow leaks in tires. Nitrogen is completely dry, so it eliminates the potential for condensation.
I plan on using it in my bicycle tires which I inflate to 120 psi. On a warm day I can loose 5lbs or more. The molecules escape more easy the warmer the tires gets.
I'll post bike results when I do it.

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Oh no not the molecule size argument. If that were true, then I could just overfill my tires a bit. After a while my tires would have only lost the 22% oxygen I would have 100% nitrogen - for nought. Or just refill the remaining 78% a bit, and voila, 95% nitrogen.

As for the dryness, compressed air is equally dry. that's why compressors have water drains. Anybody falling for that argument never did any scubadiving.

 

+1 .... Just another argument in the snake oil salesman's toolkit. I think we all have had tires that have slowly lost pressure but if you think about it, you, like me, probably have had plenty over the years that have not and therefore how does one then explain the diffusion theory of oxygen loss vs. nitrogen. It just doesn't hold water...so to speak.

People get fixated on the trance put forth by the SO salesman and forget all the other (obvious) potential sources of leaks: valves, valve stems, multi piece rims, weather checked tires etc...

Brock

 

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Fill them w/ helium because its lighter and you get better gas milage and performance and you'll get high pitched burnouts.

 

I filled my front left and rear right with Nitrogen, then regular air in the other two. After two miles it was plainly obvious the differences.


GT

 

HYDROGEN. Use tie downs to keep car from floating away.

 

You can't use helium nuclei in Ferrari tires.

They're Alfa particles.

 

Molecules matter. But for regular use air works fine. I have "air" in all 4 tires of my F355. Now when I go to work my 737 has Nitrogen in all 6 tires. Nascar style!

 

Anyone with your knowledge of "scuba" has never filled a tank before.

Dive air compressors are equipped with "purifiers" to clean the air, filter the air, and lastly DRY THE AIR. A shop compressor doesn't have molecular sieves to dry the air like an SCBA fill compressor.

Air inside any compressor exceeds 100% Relative Humidity, water deposits in the receiver, you now have air stored over water at an elevated temperature. Humid air, not dry air comes out.

PHYSICS just IS!

 

I too work in Aerospace. All my vehicles get free N2, but from a local tire shop. N2 seems to be more stable, ie I can let a car sit for a few weeks and it does not flatspot or shake the tires when first moving and warming up. i would not pay $$$ for it, but it does seem better than "shop air" here in the humid South.

 

Physics, yes. Within the tank of an air compressor you will get condensation because compressed air can hold a lot less water vapor than outside air. The water condenses out of the air because of the pressure.
And indeed you're right, air from a 200bar container is not equally dry compared to air from a 10 bar container. And yes the air coming out is 100% RH. However, that's 100% RH at 10bar, not the 2 bar in your tire.
The percentage of water in the air in your tire at 2 bar is therefor very low, and not noticable for any street driven car.

The main reason scuba compressors use dryers/condensors is because they are multistage and the condensate of the previous stage can hydrolock the next. Conclusion: if you are seriously bothered by water in the air of your tires, get your air from scuba bottles...

 

I have broken down many a tire with more than a cup of water inside them.... just a fact of life that came from some pretty wet compressors back in the midwest. Even with multiple dryers on the (poorly plumbed) shop air lines, bead blasting became a wet situation.

That gave me a chuckle...... I can remember painting my TR4 in a Mpls garage when we were first married living in a rental house..... my SCUBA tank on my back, removed the mouth piece and plumbed it to my paint gun. A REAL BUGGER to get down low enough to do the rocker panels but I was young then and my little compressor was too wet and wouldnt keep up..... Two tanks is all it took to do an engine bay and the full body, primer to top coat. I can still remember clear coating over the big moth that landed on the hood bubble...... and stayed there as a trophy for the next 20 years. Ended up buying the neighbor some new shirts as she had just hung her laundry out when I turned a big fan on...... memories.....

 

LOL! OK so now we know how you got the "twitch". How did you loose the clumps of hair?