Triumphrat

spank86 · 12-31-2012, 06:31 PM

I've been told I think too much.

DaveM · 12-31-2012, 06:33 PM

Quote:

Originally Posted by spank86

I've been told I think too much.

Yeah I get that all the time...................

downhill · 01-02-2013, 05:04 PM

Complete crap if you have to pay extra for it.

A few points; PV=nrT is Boyles Law (or the Ideal Gas Law). This means pressure in the tire will increase as the temp increases; no exceptions even for N2. Anybody who says differently is lying or ignorant.
It is the Ideeal GAs Law and no gas is actually ideal. Water vapor causes air to behave inconsistently and the at pressures above 1 or 2 PSI. The pressure change per delta T is harder to predict as a result of the water vapor.
It's no secret how very minor changes at the tire (pressure, stagger, etc.) can effect the handling of a race car (and those effects multiplied as you go faster), N2 was a way to more predictably control some of those parameters.

So why doesn't it matter on a street car?
-Your vehicle (tires/suspension) is not tuned finely enough to be affected by the differential between N2 and atmo air. Racers very carefully adjust things like pressure and stagger to spefic tracks and conditions. Street cars are running basic OEM set ups on a wide variety of turns (camber, crown, radius, surface, etc.). Even if you're running some custom set up, I'll bet you never checked stagger.
-Race car tires typically operate at 180F and higher so delta between static and operating temp is significant. Even at that T delta, the difference between N2 and air is pretty small (but at 200 mph, where an .125" of stagger can be huge, it matters). Your tires should never approach that on the street so the already minimal difference in pressure delta between N2 and atmo air is further limited.

I really love the whole N2 molecules are bigger so they don't leak out. Any gas will permeate through a tire and the differences in molecule size are fractions of an angstrom. I suppose that that N2 might diffuse through a tire wall at a slower rate than O2 but, since air is 80% N2, if the difference is really significant (it ain't) I'm thinking after the second or third refill, my tire wiould be almost all N2 (since only the O2 is leaking out). I may be anal about it but the truth is, on my car I check, and adjust my tire pressure at least weekly or if there is a significant temperature change. I check and adjust every time I ride the bike.

N2 won't hurt anything but doesn't really help either so I wouldn't pay for it. If you're checking and adjusting pressure as often as I think you should it would be pretty inconvenient to run to your local tire shop that often. It would be cool to have a tank of N2 sitting around but what do you do on the road?

73T140 · 01-02-2013, 05:11 PM

Quote:

Originally Posted by Ahks

Which is why the whole idea is a laugh, mostly. Unless you have a highly corrosive environment like here in the salty winters. Add that to really cheaply manufactured alloy wheels and you get oxidized bead seats and perpetual rim leaks.

Not as much of a problem on bikes as they arent driven in salty snow as much

And almost no problem for you in TX unless you live in the panhandle (or on the gulf

) with their high salt content soil and ground water

Gotta love Texas, not only are the taxes lower, but it seems the air is cheaper too!

triplestrength · 01-02-2013, 05:13 PM

That's a really good reasoned explanation Downhill, and I accept what you're saying, so why do they offer it for free?
Seems a bit pointless to me.

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PopPop · 01-02-2013, 06:13 PM

Because they want to keep you coming back to spend your money on other goods and services. And it's free? How do you know what the heck they're pumping into your tire, in terms of concentration of gas? I'm a little skeptical of the whole thing.

dogtired · 01-02-2013, 06:32 PM

Quote:

Originally Posted by Billbikes

I'd fart in the tires, but the nozzle sounds painful....

It is knowledge like this that keeps me coming back here.

Quote:

Originally Posted by boudiepitbull

I was thinking of trying pure hydrogen...

"Oh! The Humanity!"

downhill · 01-02-2013, 06:36 PM

Quote:

Originally Posted by triplestrength

That's a really good reasoned explanation Downhill, and I accept what you're saying, so why do they offer it for free?
Seems a bit pointless to me.

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Marketing, I mean them thar Nascar fellers use it, it MUST be better.

Seriously, the manufacturers of the N2 generating equipment use the same silly arguments on the tire retailers that the retailers use on the buying public. As for the cost, it is very cheap when you calculate the per fill price. Although around here, N2 fills are only free if you purchased the tires at the provider. Show up as walk in to get your tires checked/filled and they'll charge extra for N2. I've seen as much as $10/tire.
A few years ago, tire shops with N2 were limited and it set them apart. It's now to the point where if you don't offer N2 your shop is backward. The exotic has become the expected. When I walk through the parking lot at work, I'm amazed at how many of those green valve caps I see. I hope they came free with the tire. Like I said, there's nothing wrong with N2 but do not pay a dime extra for it.

triplestrength · 01-03-2013, 01:18 PM

With all due respect, in the UK I could count the number of people who I know who've heard of NASCAR on my fingers and toes none of those 15 people would watch it or even care about it (sorry)
Any way I'm off to our local (ish) tyreshop tomorrow for the MOT on my wife's Bonnie I will demand answers!

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norton74 · 01-03-2013, 02:25 PM

Quote:

Originally Posted by triplestrength

The theory as I was told goes a bit like this.
The nitrogen molecules are the largest size of molecule that make up air.
The others are smaller and more likely to leach out during use. As tyres and rims are to some extent permeable the oxygen etc leak out. So we lose a little pressure.
The other factor is that nitrogen does not expand when hot in the same way air does so the tyre should stay at the same pressure constantly.
Now this stuff wasn't around when I was a tyre tech so I'm only repeating what my old employer told me. He also felt that the nitrogen issue was "small potatoes" as far as bikes were concerned.
Me I wouldn't bother as I have my own compresser with a vapour trap.
And always check tyres before riding, but for some it might be useful.

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The amount of empty space between molecules of nitrogen gas is so great relative to the size of nitrogen molecules makes any difference in size with oxygen molecules to be meaningless. The size difference between oxygen and nitrogen molecules is only about 3%.

Air and pure nitrogen follow the perfect gas law pretty well. This law states that at a given pressure, volume, and temperature, the number of gas molecules is the same no matter the composition.

If you are paying for nitrogen in your tires, you're paying someone else's mortgage.