The heat generated by tires isn't from the gas inside, it's from the sidewalls flexing as the tire rolls down the road. So I can't quite see how nitrogen would keep the tires cooler either.

I understand that nitrogen doesn't expand at the same rate air does, given identical increases in temperature. But that's an effect of heat, not a cause.

 

The tire temps that I've measured are not collected in a really precise manner. After each run I poke the temp sensor in the tire tread and measure the temp. We didn't run back to back air vs. nitrogen, we made the switch at the begginning of a season and never looked back. Our tire temps are usually well over the boiling point of water after a couple laps. 5-10 degrees would be within run to run variation.

We did see less pressure rise after switching to nitrogen. That has made the race car more consitant over a given run.

 

True... but the nitrogen takes roughly 20% more caloric input to heat up to the same temperature. So the tires may (don't know for a fact because I don't have the means to test them while driving) take onger to heat up as fast, or if not the tires, at least the internal gas temperature and would therefore have more consitent gas temps and pressure.

For short track runs the external tire surface temps can be heated up with a burn out as people normally do, but successive runs (or towards the end of a single run) I'd imagine that tire pressure would stay more consistant when nitrogen filled, especially since the amount of water vapor in the tires is much lower.

All of this, on both sides of the debate, is pure conjecture without data. Some has already been provided from ancedotal testing on tracks, but I wish we could get information from Ford or some other source's tire testing. I've seen Ford's equipment... very state of the art. Not only can they test tire wear, but they can test temps as well under a variety of loads and also under considitions that simulate the tire going against the direction of the vehicle. For instance, they can turn the tire to an angle of the simulated road surface under it. The resulting tire squeeling is ear piercing even when you're in a different room watching the tests through a thick transparent shield. I'm sure the tire companies have some of this data but obviously its proprietary and we're not likely to see it.

For a race care, consistency is everything and its a no brainer to inflate them with nitrogen, same thing with aircraft (the USAF fills its air plane tires with nitrogen). For them, the added cost is trivial compared to to the overall costs of operation so its no brainer. That's why I believe its not something the average Joe should pay for, but if the tire shop offers it for free its something worth considering. For what its worth, I don't run nitrogen in my tires but may consider it the next time I take my truck to the track if I plan to make more than a single pass. On the street, the PSI in my tires is set to so the tires are right were I want them when warmed up but it would be nice to know they stayed more consistent.

Granted, my ride is geared toward performance, so it would be nice, but I can't make a cost justification at this point for the majority of my driving.

 

Right, the higher calorie/degree rise in temperature for N would cause the tire to heat up more slowly, but given enough time (and/or heat) the tire should reach the same temperature as with air, as the heat transfer *away* from the tire is presumably the same with air or N inside...

And also - the N at Costco isn't "free", you can bet it's part of the price you pay for the tire, rather than coming out of the CEO's salary...

 

ok but Costco tires are chepper then most anywhere else, they also roate and balence, and patch holes for free for life, so if its costing a bit more for the N who cares its still a cheeper tire.

 

Huh?

I didn't say not to buy tires there - heck, I buy a lot of tires there myself. It just cracks me up when folks think they're getting something like that for "free". Costco's already low prices might be a bit lower if they didn't use N fill... rest assured, you pay for it...

 

I honestly can't believe there are educated, intelligent people who believe this latest snake oil pitch. If it is 100% free then it might be worth the price but like Jim said, you are paying for it somewhere, somehow.

And people say I wasted my money buying a hybrid vehicle?

Here is a pretty amusing article about it. There are thousands of scientific writeups dispelling the myth and there are very few (except those by the folks selling N2) saying it does a darned thing for street-driven vehicles.

Nitrogen Filled Tires: a Scam? Hot Cup of Joe

 

< sarcasm on >

An knowledgeable write-up by an anthropologist on nitrogen in tires. I bet he knows a lot more about it than every airline in the western world, the US military, scores of race teams, and fleets of long distance trucks who have done temperature comparisons, etc.

Also, NHTSA tests showing reduced aging of N filled tires must be entirely bogus and made up. I bet they were paid off.

Consumer Reports test showing nitrogen filled tires lose less pressure must be wrong too (and their test was just on tires left outside, the difference would have been even more dramatic on driven tires since nearly 30% of all tires driven are 8 psi low on pressure). I bet Consumer Reports was paid off by the nitrogen industry.

All those state, county and local police agencies using it... they must be off their rockers.

The ExxonMobile study using tires inflated with 99.9% nitrogen which found it reduced static air loss by 45%, a corresponding reduction in the rate of aging and improved tire performance.... gotta be bogus.

< sarcasm off >



There's no snake oil here... its valid stuff. The only thing about it which is snake oil is the rip-off pricing because I don't believe the cost benefits are there for the price, except for someone who never checks tire pressure. Considering the minute cost to produce the nitrogen there really shouldn't be charge of more than pocket change per tire. However, the fact is tire companies thrive off of people who ruin tires by driving with under or over inflated tires so they stand to take a loss due to less sales because of properly inflated tires you can be they'll make it up by charging through the nose for the privilege to put nitrogen in the tires.

 

Now I'm saying this a bit tongue in cheek, because general wisdom would be that all those folks that Ken lists *can't* be wrong, but...

First, remember we're talking about the difference between 78% N and 100% N, so that would make one all the less convinced.

But also think about this: if N holds pressure better than room air because N molecules are bigger, and thus don't leak through the tire casing as rapidly, then what *does* leak through must be non-N, right? That means every time you top off the pressure in your tires with room air, you're actually increasing the N percentage in the tire. So eventually you should end up with close to 100% N, right?

 

Now there is a thought. A tire is really a device for producing pure nitrogen!

 

I said it was amusing, not credible.

Airlines, the military, race teams and so forth have completely different operating parameters than street driven cars. High altitude, very high speeds, much higher wheel loading, etc.....

And so far noone has been able to explain why tires that leak with straight air don't just leak the O2 and ultimately end up with just the N2 remaining. If the N2 doesn't leak out, then wouldn't this be the case?

Also, noone has explained why tires mysteriously don't leak around the rims or valve stems when filled with N2.....

My tire pressure is checked almost religiously and I don't have a problem with decreasing tire pressure caused by the air bleeding through the pores in my tires. If this part of the justification for N2 were true, wouldn't my tires just go flat after a while.

 

If your car sits there long enough, the tires WILL go flat.

Also, WRT to the cost issue. If I go to Costco, and tell them NOT to use N2 in my tires, do I get a slight discount?

No? I pay the same amount whether they use N2 or air?

Gee, it doesn't sound like having them put N2 in my tires is costing me any extra then.

 

Ok, so by that logic, if I need a new remote for my tv, but can't buy it separately, so I buy a whole new tv just for the remote, then I actually got a second tv for free!

 

Ummm...boiling point of water at what pressure?

Check out this graph:

http://www.engineeringtoolbox.com/do...emperature.png

Keep in mind that atmospheric pressure is 14.7 psi. When you measure a tire, you're actually measuring the difference in pressure between the gas in the tire and atmospheric pressure (commonly known as 'psig')--so a tire pressure gauge reading of 32 psi is actually about 47 psi absolute pressure. According to that graph, the boiling point of water at 50 psi is about 280ºF.

Something to think about.

Jason

 

What about the other studies, such as the Exxon/Mobile, Consumer Reports, and NHTSA studies, which were for street tires? You seem to have overlooked those. Are they not credible groups for studies?

No one has said what the end composition is one way or another. Does it matter, or it is just a tangent?

No one said they didn't leak around the rim or stems when filled with N2. Its just that its leaks less, overall, than straight air.

Maybe you have unique tires, blessed by the holy poobah of tiredom ? All other rubber tires, however, will go flat eventually if not topped off. Some fast, some slow, but in a matter of a few months, or 2-3 years, they will all end up either completely flat or severely underinflated. That's why statistically about 30% of the tires on the road are at least 8lbs under inflated. They didn't start out that way when they were mounted.

You don't have to take my word for it, there's all kinds of information about inflation leakage on the majority of the tire manufacturer we sites.