HIGHSURVEY

Just had a set of "mudders" installed on my off road and part of the deal involved filling the tires with nitrogen. I have just recently become aware of the practice and , up till now, thought it a waste of money (not much - $8/tire). Seemed to me that expensive air will do no more good in the tires than ordinary air. The Tech gave me the logic that the Nitro molecule is larger than the air and as such will leak out more slowly than air. (Claimed that all tires lose air at a slow rate even w/o a puncture) Huh??? Also claimed that the "N" molecule, being larger will not expand with heat as much and therefore not vary the pressure as much with temp changes. Anyway I got to wondering if any of this logic could be applied to the P Zero's on my 997S Cab. Any opinions on Nitrogen?

Steve-o

I don't have nitrogen tires on my Porsche, but do have it on my truck and on the wife's Jag AND there's no noticible difference. In fact, it's a pain to increase pressure as I can't use my compressor, but have to take the cars back to the tire shop. I paid extra for the nitrogen tires and regret it.

HIGHSURVEY

Steve-o you bring up another point I was wondering about. Can you just disregard that you have Nitrogen in there and just fill up the tires as usual? Basicaly - can you mix the two?

jhbrennan

I didn't pay for the nitrogen but do have it and the only discernable benefit that I've seen is that the pressure stays rock solid. For 4 months with temperature changes ranging from 60 F to 100F my psi in each tire has remained constant.

points

Same here.

mglobe

Seems silly to me. "Air" is 78% nitrogen.

HIGHSURVEY

mblobe - good point!

PTEC

I was a critic of it until I tried it. I aired up my tires with nitrogen and then check the pressures about 3 months later before a road trip. Not a half psi missing. I was impressed.

george_k

If your serious about using nitrogen, it might pay to look at buying your own cylinder and regulator - for an example of a possible setup look the items listed below at http://www.mcmaster.com.
Cylinder can be filled at any welding shop hold 20cu ft @ 2000 psi which should fill quite a few tires, cylinder fill is approx $20.
You would need the following:
p/n 7897A65 - Pressure Regulator Std Duty, 1-Stage, Nitrogen, 0-100 PSI
In stock at $96.55 Each ( this has a special welding hose fitting on the outlet which can be removed, then it will accept a standard 1/4" air hose)
p/n 7822A11 High-Pressure Inert Gas Cylinder Cga #580, 20 cu/ft Capacity, 14" High, 5-1/4" Dia
In stock at $94.95 Each (shipped empty)
Plus a 1/4" tire hose and tire fill chuck
For approx $220 investment and you have the convienience of being able to fill all of your tires with nitrogen in your own garage.

Edgy01

I have them fill mine up with only about 79% nitrogen.

Of course this is silly. It's all marketing. I noticed one time that my local tire shop was charging $4 a tire for this 'service.' When I was in there earlier this week I said no nitrogen. Wasn't debated at all and I never got the charge.

All it is is one more quick easy way for a tire shop to extract more money from you. If they want to do it for free (a la Costco) then it's fine.

Mike Murphy

Air is 78% Nitrogen with X% humidity. If you fill up with 100% nitrogen, chances are, you are getting very low humidity. The key is this humidity content, not necessarily the % of nitrogen vs. oxygen vs. hydrogen vs. carbon dioxide (which is all part of regular air).

If you're getting tires at Costco, then sure, put in the 100% nitrogen because it's free. Otherwise, I would fill your air at a shop that has a good air compressor with a good dryer install in-line to ensure that you're not filling your tires with air + moisture.

911Dave

I couldn't agree more. So your pressures stay constant a little longer....so? Who cares? I have air in my tires and none of them have lost a pound in 5 months. If one drops, I fill 'er up. I have to think that leakage depends on the quality of the seal and the integrity of the valve more than what kind of gases are inside the tire.

8haggis

The original reason for N in place of air more consistent pressure at various temperatures. This is important for racing and this is where it is used. If the pressure in the tire changes with temperature (caused mainly by the humidity others were speaking of) then the contact patch will change and this will alter the handling of the car.
Unless you are driving a F2007 Ferrari F1 car, skip the 100% N and just use the 78% stuff.

cviles

Nitrogen is a gas, and like any other gas it expands with temperature according to the ideal gas law: pV = nRT. There is a direct correspondence between temperature and pressure of a gas in an enclosed space.

The amount of pressure increase depends on the density of the gas and the amount of it present. "Air" is a mixture of gasses; about 78% N2, 20% O2, and some other trace gasses. The benefit to filling tires with Nitrogen is it's dry (no water vapor). Water vapor can corrode pressure monitoring sensors and water vapor expands at a different (higher) rate than nitrogen or plain air.

There's no harm to adding some plain air to nitrogen filled tires from a hand or portable pump. Trust me, your tire shop didn't hook your tires up to a vacuum and evacuate all the air before adding the nitrogen. There's still "air" in your tires and adding a bit more won't hurt.

H20NOO

When I worked with a Star Mazda Pro team we always used nitrogen as did most of the other pro's across a variety of series. The benefits were allegedly, less tire pressure fluctuation during heat cycles (practice, qualifying and race). Don't know about the leakage issue but it did seem that nitrogen was the standard among race teams.

MC