Hi Tim,
1. Consumer Reports did a test using tires from a previous tread wear study. If I am not mistaken the nitrogen tires lost 30% less than air filled tires over a years time. That also does not take into account the special silicone insert green tipped valve stem caps that are included with a nitrogen tire inflation to reduce leakage further.
2.Water vapor in the tire will contribute to increases and decreases in tire presure causing minimal additional wear and reducing tire life. I too have never seen a tire rot from the inside out.
3. The nitrogen tire inflation systems purge the air from the tire and you end up with around 95 - 98% pure nitrogen.
4.Tire pressures can fluxuate up to 10% from cold to hot. Thats 3 or 4psi. This won't happen with nitrogen, leaving you with more consistant handling and reduced treadware.
5. As for weight. You are correct, the difference is probably only several ounces per tire. But then again as the quarter mile track and street racers say, every ounce of rolling resistance you drop is worth something. Considering we already have lightweight tires and rims it just might be worth a shot. After all we just spent several thousand more for a hybrid, whats an additional $30 that might save us some gas in the long run?

Sincerely,
Blind Mike & Michelle
TwoLostMinds

 

Where are you getting this information from? Why won't nitrogen heat up? Regardless of the gas inside, the tire will flex as it rolls and that will generate heat. Universal gas constant shows that as you hold volume and mass constant, an increase in temperature produces an equal increase in pressure.

 

Good old Consumer Reports. Comparing apples to pears. It would have been nice if they went to the trouble of putting the same caps on air filled tires...just to be sure.

As for rotting tires, I think this belief comes from the fact that larger vehicles like trucks and airplanes may benefit from Nitrogen.....because those types of tires are often retread over and over again. Whereas car tires are not.

While the Nitrogen tires will fluctuate less, it is not quite the magnitude that you are quoting. Its not like they don't fluctuate at all, its just a little bit less....which is really only critical for high performance race cars where dialing in performance can mean a few hundredths of a second.'

The only way this will improve you gas mileage is if you don't check your tire pressure regularly. Nitrogen filled tires do tend to hold the pressure longer than air filled - even if it might only be the fancy green caps! If you lose 1PSI per month with air and never check your tire pressure you will get worse gas mileage as the pressure drops. If you put in Nitrogen you would lose less tire pressure and get better gas mileage over the same period.

I don't think Nitrogen would ever be "worth" paying for. If it was free, sure, its a nice safety net for tire pressure if you forget to check. In reality, it would be cheaper to check your tires once a month and top them off with free air.

My conclusion: If you can't be bothered to check your pressure, then by all means put Nitrogen in your tires. If you want to save gas and money, check your tires regularly and keep them properly inflated with air.

 

I will not recommend exceeding Max Sidewall PSI to anyone, however I dropped the 52psi after the steady state speed test and run my stock tires at 50psi. My tires have 48,900 miles on them now and found a big decrease in wear and better handling with the higher pressure. There is one tire that leaks about a pound a day and I can tell a decrease in mileage when that one tire gets down to 45psi. Also, I can see a decrease in coasting speed faster in neutral when that tire gets to 45psi.

I have read the San Jose Police Department has increased tire pressure in their training vehicles above Max sidewall to save money on tire wear. They also said they don't go above sidewall on their street cruisers for liability reasons.

With the higher pressure, there is a decrease in the tire patch on the road surface. I've found that with less tire surface on the road, hydroplaning on wet roads is reduced. Sounds strange I know, but think of the tires as a ski on water. The bigger the ski, the easier it hydroplanes.

One last experience, I was in a rollover condition at 70mph and I feel it was the higher pressure that helped prevented it.

GaryG

 

Let me rephrse...95 - 98% pure nitrogen will expand and contract to a far lessor degree than regular air in the tempurature range that a tire will experience. I remember reading that an air filled tire filled to 32psi @ 70 degree's will be 28psi at 32 degree's and 35psi at 100 degree's.

I'm not saying that Nitrogen is a perfect sollution but with airlines, nascar, quarter mile cars and street tuners using it. Plus some manufacturers now shipping cars with Nitrogen in the tires it must have some typical street driving value. ... Just my laymans oppinion.

M&M
TLM

 

Again, I'm wondering where you're getting your information that nitrogen doesn't change pressure to the same degree as any other gas. It has been a few years since my days majoring in physics, but the laws regarding gas pressure are pretty clear. Pressure = Temperature*Mass/Volume. So if you hold mass and volume constant (which in a tire you are) there is a direct relationship between pressure and temperature that doesn't vary between gases.

 

ideal gas law
PV=nRT
where

P is the absolute pressure (SI unit: pascal)
V is the volume (SI unit: cubic metre)
n is the amount of substance (loosely number of moles of gas)
R is the ideal gas constant (SI: 8.3145 J/(mol K))
T is the thermodynamic temperature (SI unit: kelvin).
(The law works with any consistent set of units, provided that the temperature scale starts at absolute zero, and the appropriate gas constant is used.)


Considering the absolute gas law as above, it should be clear that the differences in pressure will be miniscule with the same change in temperature. The only variable would be n, the number of moles of gas. Comparing 100% nitrogen with room air, approximately 78% nitrogen, 21% oxygen, and a very small amount of water vapor, the difference in number of moles of gas total would be marginally different, thus no significant difference in pressure. The presence of oxygen may lead to increased oxidation of the rubber inside the tire, but I am not aware that this is amount of oxidation is significant. phil

 

My point is not that air filled tires don't fluctuate, its just that nitrogen filled tires will not fluctuate to a measurable degree as you seem to believe. If the air tires drop 4 psi maybe the nitrogen tires drop to 3.8 psi. Really, it is not "a far lesser degree" it is a marginally smaller degree.

Again, Racecars and airlines have different reasons for using it. Racecars because miniscule differences DO matter in those sports. Airlines because of the apparent safety of nitrogen over air during landings. As for "street tuners" and manufacturers.....well, the street tuners are copying the race cars even if it is useless to their performance (like putting on a giant wing). And the manufacturers are just going with the current hype....probably even charging more for it.

 

Kind of a side thread for this discussion but as folks talk about tire pressure, esp. when pushing the rated limits, what kind of guage are you trusting to measure psi. I typically use my $2 pocket gauge and I wonder if that is even +/- 3psi. So if I want to push right to the rated max, what should I use and trust to measure?

 

Tim,
My information comes from many sites on the web. FAA, NASA, NHRA, NASCAR, Consumer Reports, Our Military...they all have contributed to what I have learned. Unfortunately I never contemplated having to debate using nitrogen so I did not make notes of references over the past few months. My suggestion is that we agree to disagree. You won't use nitrogen and when we get our FEH we will. All I ask is that unless you don't bash it as snake oil without proof.

Have a great one.

Blind Mike
TLM