Nitrogen in Prius Tires?

<div class='quotetop'>QUOTE(Danny Hamilton @ Jul 3 2007, 04:15 PM) [snapback]472507[/snapback]</div>

Right. This obviously follows from your previous explanation. However, looping back around to my original point, if you fill your tires with pure nitrogen, you will have to check your tire pressure and fill your tires less frequently. Moreover, the amount of oxygen that will diffuse into your tire will be so inconsequential (compared to the amount of nitrogen in your tire) that you will probably not measure any significant increase in tire pressure. Again, this assumes that oxygen can diffuse through the tire wall.

 

<div class='quotetop'>QUOTE(Tempus @ Jul 3 2007, 01:05 PM) [snapback]472334[/snapback]</div>

Plus, argon is more expensive than nitrogen, so it must be better!

 

<div class='quotetop'>QUOTE(Betelgeuse @ Jul 3 2007, 05:32 PM) [snapback]472522[/snapback]</div>

Correct. You would gain some pressure from oxygen intake, but it would be less than the amount of oxygen lost if filled with air. Either way the system would settle to the same value, but would require topping off at the start when using air.

Of course this is just an academic example, since the nitrogen and oxygen molecules diffuse through rubber at the same rate (slowly, in both cases).

Tom

 

<div class='quotetop'>QUOTE(qbee42 @ Jul 4 2007, 07:36 AM) [snapback]472843[/snapback]</div>

OK. Just to close the loop on this, do you have a citation for this? Almost every page I've read on this (even the ones that are against nitrogen in tires) have suggested that it is true that nitrogen diffuses through the tires more slowly. Depending on where you read, this ranges from "3 times more slowly" to "6 times more slowly."

Just as an example, here is a figure from the web page of the "Get Nitrogen Institute" (clearly an unbiased source ) which suggests that it is true that Nitrogen has a slow diffusion rate. Now, it's actually impossible to get any information from that figure since they don't put any units on it, but this is the type of thing that's out there.

If you have information on the actual diffusion rates, I would drop this whole thing.

 

<div class='quotetop'>QUOTE(Betelgeuse @ Jul 4 2007, 10:30 AM) [snapback]472866[/snapback]</div>

r, the rate of diffusion is approximately inversely proportional to the square root of the molar mass, M.

it follows that for two gases with molar masses M1 and M2, the two respective rates of diffusion, r1 and r2, are related to the two molar masses by the following relationship:

r1 / r2 = sqrt (M2 / M1)

the molar mass of N2 is approximately 28 g/mol
the molar mass of O2 is approximately 32 g/mol

let 1 = N2
let 2 = O2

r1/r2 = sqrt(32/28) = 1.07, so the rate of diffusion of N2 is 1.07 times than that of O2

For reference, I suggest the CRC Handbook of Chemistry and Physics.

A quick search of the web revealed a couple of useful sites:
http://hyperphysics.phy-astr.gsu.edu/hbase...etic/henry.html
http://chem.salve.edu/chemistry/diffusion.asp

Tom

 

YES replacing the air with nitrogen does make a difference in mileage, I was at an average of 43mpg now that I had my tires filled with nitrogen. I'm at about 47-48 so it's not HUGE! But since I drive about 25-30k a year it will make a difference, you do the math!

 

Amazing Thread.
I don't understand 2/3rds of it.
I believe however the PSI you maintain will have much more impact on your vehicle than what you maintain that PSI with.
For myself, I like the idea that I can monitor, maintain my tires PSI using "Air" and a Compressor as opposed to being a slave to the dealership or some other entity that uses nitrogen. In other words? The convenience of simply using "air" trumps any arguable or debatable advantage using Nitrogen may or may not represent.

 

This is a really old thread. There are some more recent nitrogen threads, probably better. The main benefit of N2 is just that the tire holds pressure better (N2 diffuses about 4x slower than O2). But since air is 79% N2 anyways, this is not such a big deal, but it helps. If you check pressure regularly, the impact of N2 filling is not significant. Nonetheless I wish more auto cos. and tire places would fill new tires with N2. Further refills could be just air but I like the idea of starting out with clean dry N2. Since the O2 diffuses faster the N2 will tend to concentrate in there in any case.

 

I have nitrogen on my tires the problem that I have is that here in Dallas that a lot of dealers do not offer nitrogen . my dealer does but their always filled whit cars and I have to wait half and hour to an hour to fill an tire whit low pressure so sometimes its just easier to filled whit air and that kind of takes away from having nitrogen in the tires . so I would also recommend for someone thinking of getting nitrogen in your tires to consider this advice because now that this has happened to me I think I would have been better just putting air.