Nitrogen Tire Inflation

Status
Not open for further replies.
T

TwoLostMinds

Joined
Feb 12, 2005
Messages
28
Location
NJ
Hey all,

Forgive me if this has been discussed before. I tried doing a search for "Nitrogen" and kept getting an error.

We ordered an 09 Ford Escape Hybrid and should be taking delivery sometime between September & November. The dealership recomended we purge the air in the tires and fill them with nitrogen to help maximize the benefits of the low rolling resistance tires. They cited that nitrogen will weep more slowly from a tire than air, it is dry(causing less internal tire ageing) and it runs 20% cooler than air inflated tires(reducing rolling resistance, tire ageing and tire presure changes). I am skepticle but the dealership is offering to do it for free($39.99 value) and I found a local welding company that will top off all four tires (when needed) from a nitrogen tank for $2.
I've seen documents online from Ford (John Baldwin, Ford Motor Company - presented to Rubber Division, American Chemical Society) stating that nitrogen reduces tire ageing and (in fleet use) improves overal fuel economy. Michelin at the CEC workshop states that the 20%(aprox.) reduction in running temp reduces rolling resistance and tire ageing, improving fuel economy.

Knowing not to believe everything we read on the internet and definately not believing everything we hear from a dealership, I would like you opinions please. If possible, please back up any negatives with documentation and resources.

Thanks for all your help
 
The advantage of nitrogen is in the lower water content so they do not have large pressure variations through temperature. Compressed air through a good air dryer is quite close in performance for that, but I think the push on nitrogen about aging is the less oxygen, the less oxidizing that can happen.

I'd take it for free.
 
Here's one of the past discussions on the subject:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1129803&fpart=1

There are more in the archives.

My question is, how do they remove all the "regular" air that's stuck in the tire to ensure that you end up with pure nitrogen?

The improved fuel economy claims are a bit hard to swallow for me. Maybe they stem from the fact that most people that do not use nitrogen forget to pump their tires as the temperatures drop in the winter time, so they end up driving on underinflated tires - this in turn negatively affects fuel economy. That I can believe.

As for the aging factor, in my case, I never keep my tires for more than 3-4 years anyway, so extended life is not much of a benefit for me. Besides, tires also age from the outside - exposed to sun and other elements. Nitrogen is not going to prevent that kind of aging.
 
Originally Posted By: Quattro Pete
Here's one of the past discussions on the subject:
http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1129803&fpart=1

There are more in the archives.

My question is, how do they remove all the "regular" air that's stuck in the tire to ensure that you end up with pure nitrogen?

The improved fuel economy claims are a bit hard to swallow for me. Maybe they stem from the fact that most people that do not use nitrogen forget to pump their tires as the temperatures drop in the winter time, so they end up driving on underinflated tires - this in turn negatively affects fuel economy. That I can believe.

As for the aging factor, in my case, I never keep my tires for more than 3-4 years anyway, so extended life is not much of a benefit for me. Besides, tires also age from the outside - exposed to sun and other elements. Nitrogen is not going to prevent that kind of aging.




Thanks for the link from the archives. They fill and purge the tires a few times to remove as much moisture as possible and you end up with between 96 and 99% purity.
 
Originally Posted By: Quattro Pete
The improved fuel economy claims are a bit hard to swallow for me. Maybe they stem from the fact that most people that do not use nitrogen forget to pump their tires as the temperatures drop in the winter time, so they end up driving on underinflated tires - this in turn negatively affects fuel economy. That I can believe.

I'm pretty sure that's what it is -- plus the fact that nobody ever checks their tire pressures.
 
In part nitrogen is a gimmick. It's useful for race applications because pressure is less sensitive to temperature changes. This is nice on the race track.

For consumer level use, it's just a waste. You just don't make use of the benefits. Also realize pure air is 78% nitrogen already. Plus the nitrogen you do buy is not even 100% nitrogen. I know some of the older systems were quoted as rather low barely to 90%. I think some of the new systems are more towards 98-99% now.

The problem is you now pay for what was once free, and you're paying a premium. Then you have to weigh the advantages. For example, let's consider tire oxidation/wear from the inside. Since when have you ever had a problem with the inside of the tire? Ever. Don't you think external oxidation is a wee bit more prevalent? Ok, what about pressure loss? Well, how much of a difference will it be total? 1 psi per 6 months? Exactly how much of a benefit is it?

The hard part with this is weeding through the marketing and getting to the real facts. You may see a lot of fancy numbers, but pay close, close attention to exactly what they say.
 
Originally Posted By: mvw2
In part nitrogen is a gimmick. It's useful for race applications because pressure is less sensitive to temperature changes. This is nice on the race track.

For consumer level use, it's just a waste. You just don't make use of the benefits. Also realize pure air is 78% nitrogen already. Plus the nitrogen you do buy is not even 100% nitrogen. I know some of the older systems were quoted as rather low barely to 90%. I think some of the new systems are more towards 98-99% now.

The problem is you now pay for what was once free, and you're paying a premium. Then you have to weigh the advantages. For example, let's consider tire oxidation/wear from the inside. Since when have you ever had a problem with the inside of the tire? Ever. Don't you think external oxidation is a wee bit more prevalent? Ok, what about pressure loss? Well, how much of a difference will it be total? 1 psi per 6 months? Exactly how much of a benefit is it?

The hard part with this is weeding through the marketing and getting to the real facts. You may see a lot of fancy numbers, but pay close, close attention to exactly what they say.


Yeah, I've been trying to dig through all the marketing hype and what I've found so far is....
1. Consumer Reports did a study on 31 pairs of tires and determined that air filled tires lost 3.5psi and nitrogen tires lost 2.2psi. 1.3psi loss difference isnt huge, but it is 60% less. Not significant, just means we don't have to bend over and fill the tires as often.
2. The current nitrogen tire machines out there are pumping 96 - 99% pure. They pump and purge twice to remove moisture and air then the final fill comes up to around 97% pure.
3. We, as consumers would definately not gain the same advantages as race drivers, but what I did find was that nitrogen filled tires run about 20% cooler. According to the Michelin report, Hysteria is a huge factor in calculating rolling resistance, the hotter a tire gets the more resistance it produces. I'm trying to find more information on just how much reducing the tires heat by up to 20% will effect fuel economy losses due to higher tire temperatures on the highway.
4. External oxidation is something we most likely will never overcome with rubber and rubber/silicone tires. According to the hype and one report I found in Japan, under high presure, when the tire flexes, moisture can permeate the inner rubber and cause accelerated ageing. The hype said that this can lead to premature cracks and fissures in the sidewalls and treads. I don't want to rely on the one scientific report from Japan as I don't have anything to validate its reliability.

There is a lot of confustion, overstatments and misinformation out there. I'm hopping you guys could help weed through it to see if we can either debunk or prove its validity.
 
Originally Posted By: TwoLostMinds
Consumer Reports did a study on 31 pairs of tires and determined that air filled tires lost 3.5psi and nitrogen tires lost 2.2psi. 1.3psi loss difference isnt huge, but it is 60% less. Not significant, just means we don't have to bend over and fill the tires as often.


Well, 60% of almost nothing is still almost nothing. To me, that difference is so small that it can be ignored. Whether you lose 2.2 psi or 3.5 psi over the course of the year (that's the length of time that study considered - not that CR is an authority on anything car-related), that still only translates to about one tire pressure top-up over the course of 1 year. And in all honesty, even if my tires were nitrogen-filled, I would still check their pressure as often as I do now so that I can detect slow leaks due to nails/screws stuck in tread or leaky valve stems. And if I'm already checking the pressure, then pulling out my portable compressor from the trunk and adding a couple of PSI once in a while takes 5 minutes or less.

Call me oldfashioned, but I view the whole nitrogen tire fill as a solution to a problem that did not exist. Now, if that solution is free - fine. But if that solution results in money leaving my pocket - no thanks.
 
Originally Posted By: Quattro Pete
Originally Posted By: TwoLostMinds
Consumer Reports did a study on 31 pairs of tires and determined that air filled tires lost 3.5psi and nitrogen tires lost 2.2psi. 1.3psi loss difference isnt huge, but it is 60% less. Not significant, just means we don't have to bend over and fill the tires as often.


Well, 60% of almost nothing is still almost nothing. To me, that difference is so small that it can be ignored. Whether you lose 2.2 psi or 3.5 psi over the course of the year (that's the length of time that study considered - not that CR is an authority on anything car-related), that still only translates to about one tire pressure top-up over the course of 1 year. And in all honesty, even if my tires were nitrogen-filled, I would still check their pressure as often as I do now so that I can detect slow leaks due to nails/screws stuck in tread or leaky valve stems. And if I'm already checking the pressure, then pulling out my portable compressor from the trunk and adding a couple of PSI once in a while takes 5 minutes or less.

Call me oldfashioned, but I view the whole nitrogen tire fill as a solution to a problem that did not exist. Now, if that solution is free - fine. But if that solution results in money leaving my pocket - no thanks.


I can agree with that...60% of almost nothing is nothing except in large fleet situations where the minicule fuel savings due to tire presure stability can grow exponentially.
Score:
1 Debunk
0 Hype

After doing a bit more reading I have come to believe that the tire oxidation/degradation issue due to moisture will not be easily de-hyped. So, I'll scratch that one off the list until a time comes when more reliable independant studies are found.

As for the rolling resistance losses due to increased tire heat in highway evironments.... I need someone with a greater knowledge of tires, rubber and psysics than myself to help me understand and dubunk or validate this claim.
 
I wouldn't pay for the nitrogen.
What about the outside of the tires ?
Higher pressures decrease the rolling resistance.
 
Originally Posted By: Steve S
I wouldn't pay for the nitrogen.
What about the outside of the tires ?
Higher pressures decrease the rolling resistance.

Well...for now this isnt about paying for the Nitrogen. It's about validating or debunking the claims and science.
Yes, high presure reduces rolling resistance, thats why so many pump their tires beyond the car manufactures recomendation to the sidewall max or even higher. This has proven increases in fuel economy.

Now I am trying to prove or debunk the following, thus proving or disproving an increase in fuel economy:

Definition: "Rolling resistance is the energy consumed per unit distance and is equivalent to the scalar sum of all contact forces tangent to the test surface and parallel to the wheel plane of the tire" (SAE J2452)
Units are [J/m] or simply [N], but conceptually, rolling resistance is better comprehended as a loss per distance than a force
Rolling resistance is primarily due to viscoelastic heat dissipation in the rubber
Aerodynamic drag, friction in the contact patch, and friction with the rim also contribute to the total rolling resistance, FR

Loss contributors:
Areodynamic Drag 0 - 15%
Hysteretic Losses 80 - 95%
Tire/Ground & Tire/Rim Friction
To better quantify and understand the contribution of rolling resistance to fuel economy, Schuring (1988) proposed the concept of the Return Factor (also referred to as energy ratio):

Return Factor = %Reduction in Fuel Consumption / %Reduction in Rolling Resistance.

For passenger cars and light trucks, RF is typically between 1:10 and 2:10. This indicates that a 10% improvement in RR gives only a 1-2% improvement in fuel economy.
For heavy trucks, RF can be higher, with a typical range between 1:10 and 3:10, hence the fuel savings potential for trucks may be higher than for passenger vehicles

Rolling resistance is affected by many factors, both in tire design and operating conditions:
Tire Mass
Rubber Formulations
Inflation Pressure
Speed
Ambient/Tire Temperature
Applied Drive Torque
Surface Roughness
Steer angle and camber/toe of vehicle

>>
 
All the claims they make, cannot be proven. To here the tire shop sell this to people, you would think your mileage gain would be very noticeable but don't believe it.

If it free, go ahead but never pay for it. I didn't because I have given lot of business to this tire shop and he wanted to convince me my mpg would jump. I told him recently that I never noticed anything and I haven't. My mpg is the same today as it was back in Sept 2007 when he installed the N in the GY Eagles.
 
Quote:
My mpg is the same today as it was back in Sept 2007 when he installed the N in the GY Eagles.

Now this information, unlike the rest of your paragraph is quite useful
 
Last edited:
I will note that air loss will vary by tire brand/model, how well it's sealed to the rim, if there's any loss through the valve stem, etc. For example, I have a summer set of RE01R tires. They didn't lose one pound over 6 months. My winter Nokian WRs lost several psi over the summer during storage. One also had a poor seal to the rim, losing extra air.

Tire temps will also vary greatly. Something like the RE01R tends to build and retain heat well, good for track use. A more mild mannered road tire will barely ever be warm to the touch. The heat is generally a factor of rolling friction and tread flex. Lower pressures cause more flex; harder driving causes more friction buildup. I'm not really sure how the air comes into play in this factor.

The only thing it can do is soak up and help dissipate heat inside out from the carcass to the rims. Does nitrogen transfer heat better than air? Well, if we consider specific heat (the energy needed to raise X volume (or Y mass) one degree, both air and nitrogen are nearly identical. This means both absorb and transfer heat at the same rate. So, where's the benefit there?

Well, maybe weight is a benefit. Nitrogen is lighter than air. How much? 4%, lol. Is that a lot? Well, a normal car tire carries about 1 lb of air total, and the tire plus wheel weighs 25 lbs. Well if we consider 26 lbs versus 25.96 lbs, how big of a benefit is that? About 0.2% Ok, so that means squat too.

So um... what's the benefit of pure nitrogen again?
 
Originally Posted By: rondoggnuts
TwoLostMinds said:
Quote:
quite useful


I only found this part of your post particularly useful myself.


LOL.gif
Click to expand...
 
Originally Posted By: mvw2

So um... what's the benefit of pure nitrogen again?


Thats what I want to find out....is there a benefit? And its answers like yours that are the reason I posted it here, Facts with a hint of sarcasm.
beer3.gif
 
We tire engineers have always thought that it did not matter what the gas was that was used for inflation purposes - the tire reacted to being inflated, not the inflation medium.

Here are 2 graphs presented by Walter Waddell of ExxonMobil to the California Air Resources Board on June 4, 2008.

http://www.geocities.com/barrystiretech/n2cavitytemp.jpg

http://www.geocities.com/barrystiretech/n2rr.jpg

Both of these show no difference between N2 and air for 2 very important tire properties - Rolling Resistance and Operating Temperature.

Tire Aging?

The Law of Gas Partial Pressure says that oxygen would leak into the air chamber, in spite of there being an overall higher pressure in the chamber. This has been demonstrated, but I can't put my hands on a copy of the presentation made at the Sept 2007 Tire Society paper that shows the supporting data. When I find it, I'll post it.

But in the meantime, it is expected that oxygen would migrate into the rubber of the tire - and while the overall degradation rate would be slower, it would still happen. The question then becomes how much longer would it take before the degradation would become critical. The fact that oxygen can be detected in the air chamber - and the O2 volume increases over time - and the important area is halfway into the tire (the edges of the belt) - well ..... it's questionable that this difference would be enough to warrant the expense of using N2 as an inflation medium.
 
Status
Not open for further replies.

Similar threads

L
Tire over inflation
2
Replies
26
Views
2K
zzyzzx
V
A PSA About those tire TINS and date codes: Installers, It's Dates Out, for ALL tires.
2 3
Replies
47
Views
3K
CapriRacer
R
Over inflated tire…
Replies
8
Views
1K
14Accent
G
More Discount Tire frustrations
2
Replies
32
Views
3K
chainblu
C
Rolling Resistance Increases as the temperature drops!
2
Replies
20
Views
2K
LongTime_Lurker
Back
Top