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Old 04-16-2014, 08:10 PM   #111 (permalink)
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Quote:
Originally Posted by RedDevil View Post
Like I promised I tested the air in my tires.

The fact that the rate of pressure decline went down noticeably over time also confirms that nitrogen does in fact seep out less easily.
I did not expect that.
Myth confirmed, I guess.

So, apparently there is a benefit from filling tires with "nitrogen enriched" (oxygen depleted) air. They will keep their pressure better than tires filled with plain air, as those will lose most of their oxygen.
Having said that, you will need to keep an eye on the tire pressure regularly regardless of what they are filled up with, and in the end you will end up with almost pure nitrogen anyway.
You will just need slightly more air than if you use pure nitrogen.

As for better ride quality etc; obviously even if it does make a difference it is hardly an issue as the oxygen will get lost anyway.
Hah, nice testing! I didn't think it'd work quite that well, impressive. One could over inflate the tires for awhile I suppose increased psi would force the O2 out that much faster.

I wasn't under the impression though that the benefits of nitrogen filled tires are myths, they are well known, if minimal or irrelevant to most street driven vehicles on an individual basis anyway. And clearly, the only actual FE benefit is for the less OCD among us. (ok lazy). I really have no idea why this is in the unicorn corral.

I get that individually N2 is of marginal benefit. To an individual with a fastidious personality - I think we can safely say no benefit. However, taken en masse, if every tire on earth were filled with N2 tomorrow, the effects would be profound.

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An estimated 93.5% of motorists in the EU are driving on under-inflated tires and causing an additional 18.4 million tons of carbon dioxide to be released into the environment, according to a recent analysis by Bridgestone Europe. That works out to an extra 6.9 g CO2/km for every car on Europe’s roads.

Based on the data collected in 2006, Bridgestone also estimates that 40% of vehicles consume an additional 2.8% in fuel due to their under-inflated tires, wasting 8.1 billion liters (2.14 billion gallons US) of fuel every year.

To collect data for the study, Bridgestone conducted free safety checks on 20,300 passenger cars in 19 EU countries during 2006. Only 6.5% of motorists had all tires correctly inflated, 54% had some degree of low inflation and 39.5% had at least one tire significantly under inflated (<1.5 bar or 21.8 psi). 12.0% of cars (1 in 8) were in danger of tire failure.

The free check-ups were conducted by Bridgestone at shopping centres and public car parks. They form part of the “Think Before You Drive” safety education campaign, a worldwide joint initiative between the FIA Foundation (Fédération Internationale de l’Automobile), Bridgestone Corporation and national motoring clubs, launched in 2005.

These results suggest that many motorists are unaware that a tire loses pressure naturally over time, like a balloon, and that driving on incorrect pressure can be dangerous. The loss of handling control and increase in vehicle drift rises sharply as tire pressure is reduced. Low tire pressure also has an extremely negative effect on tire durability, due to excessive shear stress in the shoulder and heat build-up from sidewall bending. The 12% of motorists identified with seriously low tire pressure face possible tire failure due to these factors.

The wear life of a passenger car tire is halved if pressure falls from 2.2 bars (32 psi) to 1.0 bar (14.5 psi). Based on this 2006 survey, Bridgestone’s Technical Centre Europe calculates that the almost 40% of motorists at risk are losing 19.3% of tire wear life—an average of 9,700 km or 9 months of tire usage (based on an average wear life of 50,000 km and annual mileage of 13,600 km).

A further 54% of vehicles are losing 5.2% of tire wear life; an average of 2,500 km or 2 months of tire usage. Adding these two groups together shows that 24.5% of tire wear is being lost through under-inflation in Europe.

Inflation pressure has a strong influence on tire rolling resistance, which is itself a key factor in determining vehicle fuel consumption. Depending on the type of road and driving style, rolling resistance represents 18% to 26% of the total force on a vehicle. Since low inflation increases rolling resistance, it has a direct effect on vehicle fuel efficiency and emissions.
So, seriously, unicorn corral? If every auto manufacturer started filling tires with N2 tomorrow, imagine how much fuel that would save over the years, how much tire wear it would reduce, and how much safer people would be. Less blowouts, for example.

All that benefit just from the simple fact that N2 molecules are bigger than O2 and leak out slower.




Another note, is the Ferrari tire gas incident with McLaren in 07. McLaren stole Ferrari's super secret tire gas formula and according to Ferrari the gas made a huge difference in tire performance. The gas was basically half r404 refrigerant and half CO2 and I guess it helped transfer heat from/to the tire>air>wheel where the wheel performed somewhat as a radiator.

I'm totally unfamiliar with how a tire actually wears and why. Does the amount of heat generated by normal highway or city driving affect how fast the tire wears to any significant degree? If it did, a tire gas that transferred heat from the tire to the wheel might have some benefit for tire longevity over the years. Say getting 55k miles instead of 50k or something like that. Just a thought I had.

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Old 04-16-2014, 09:17 PM   #112 (permalink)
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Originally Posted by GTR View Post
I'm totally unfamiliar with how a tire actually wears and why. Does the amount of heat generated by normal highway or city driving affect how fast the tire wears to any significant degree? If it did, a tire gas that transferred heat from the tire to the wheel might have some benefit for tire longevity over the years. Say getting 55k miles instead of 50k or something like that. Just a thought I had.


6 in 1 hand 1/2 dozen in the other

If the brakes are warm and the rim transfers heat well it will get the warmth then the tire will get the heat.

If the rim does not transfer heat well the tire will retain more of the road generated heat

I use my brakes so infrequently that they do not get hot - most people ride their brakes obsessively, so air ducts on the brakes and aluminum rims to transfer heat away from the tire may well be better at keeping heat down and the tires from overheating- they can get hot after a long run on a hot day.

I think you will find the gas in the tire a non factor as the gas heat transfer rate is canceled out by the rubbers heat transfer rate, the rubber sets the speed of transfer the gas will get a constant heat regardless of its transfer speed of the gas as it gets canceled or superseded in seconds by the rubbers constant heat.
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Old 04-16-2014, 09:23 PM   #113 (permalink)
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I like the test results RedDevil - my tires get 50 or more psi for years , so looks like I'm riding on nitrogen ! haha.
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Old 04-17-2014, 07:47 AM   #114 (permalink)
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Quote:
Originally Posted by GTR View Post
........I'm totally unfamiliar with how a tire actually wears and why. Does the amount of heat generated by normal highway or city driving affect how fast the tire wears to any significant degree? If it did, a tire gas that transferred heat from the tire to the wheel might have some benefit for tire longevity over the years. Say getting 55k miles instead of 50k or something like that. Just a thought I had.
First, when we talk about racing tires, it isn't wear that is causing the tire properties to change; it's the heat history and the tread compound is what is changing. To some extent the tire manufacturer can change how quickly such a change can take place - and that has been what Pirelli has been doing in F1.

I would think that the issue with the inflation gas is either about keeping heat in the tires, or getting heat out of the tires. I don't recall there being any issues of brake fade in F1 for quite some time, so I don't think conducting the heat away from the brakes is what this would be about.

Heat does have an effect on a tire's wear rate, but a) the inflation gas is not going to have a major effect, and b) the temperature affect is small compared to other things. It would be better to spend one's time concentrating on alignment and gentle driving, rather than messing with the inflation medium.
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Old 04-17-2014, 03:42 PM   #115 (permalink)
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Originally Posted by CapriRacer View Post
First, when we talk about racing tires, it isn't wear that is causing the tire properties to change; it's the heat history and the tread compound is what is changing. To some extent the tire manufacturer can change how quickly such a change can take place - and that has been what Pirelli has been doing in F1.

I would think that the issue with the inflation gas is either about keeping heat in the tires, or getting heat out of the tires. I don't recall there being any issues of brake fade in F1 for quite some time, so I don't think conducting the heat away from the brakes is what this would be about.

Heat does have an effect on a tire's wear rate, but a) the inflation gas is not going to have a major effect, and b) the temperature affect is small compared to other things. It would be better to spend one's time concentrating on alignment and gentle driving, rather than messing with the inflation medium.

Guess I should have been more specific. I know why tires wear in general, and how they break down under heat, and heat cycles, and all that. What I meant was over the life of a 60K mile tire, what are the major vs minor contributing factors to wear, given an average driving behavior.

I'm sure there is some combination of factors such as alignment, camber, driving surface, psi, # of burnouts, load, and temperature. What I was wondering would reducing the average amount of heat generated when driving would tire increase tire life in any significant manner. Probably pretty hard to test that.

As far as F1, they have both problems you mentioned. Getting heat into AND out of the tires. During the first laps the tires are too cold even with tire warmers, then later the tires are too hot and that heat causes the tires to break down. It was the too much heat part that Ferrari was working on. Here is what their results were, supposedly. I think all this info came from the italian court case vs McLaren, and the court released a PDF with the technical info blacked out, but of course they did it wrong and a non adobe pdf app could unblock the info and voila, it was public.

Quote:
What Ferrari found out though , was by using a combination hydrofluorocarbon (HFC) - based mixture specially made for use in racing tires. This mix greatly extends the performance of the tires over a number of laps. For instance in the Ferrari testing after 23 laps , tires filled with air had about 40% of the performance of a new tire , where the HFC mixture had 80% of the performance of a new tire.

The mixture of gases also allowed for a much longer tire life before bursting. Where nitrogen would last for 64 minutes before bursting , the gas mixtures allowed the same tires to last from 94 minutes to 103 minutes.
That is a ridiculous improvement. They were using the wheel as a heat dissipating radiator to increase tire life.

edit: wanted to add that the author for racecar engineering was wrong about the "specifically formulated for race cars" the gas was just 50% standard r404 refrigerant and 50% CO2.
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Old 04-17-2014, 08:10 PM   #116 (permalink)
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Tires on cars that are being conservatively street-driven for mpgs have heat rejection issues?
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Old 04-18-2014, 08:05 AM   #117 (permalink)
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Quote:
Originally Posted by GTR View Post
Guess I should have been more specific. I know why tires wear in general, and how they break down under heat, and heat cycles, and all that. What I meant was over the life of a 60K mile tire, what are the major vs minor contributing factors to wear, given an average driving behavior.

I'm sure there is some combination of factors such as alignment, camber, driving surface, psi, # of burnouts, load, and temperature. What I was wondering would reducing the average amount of heat generated when driving would tire increase tire life in any significant manner. Probably pretty hard to test that..........
Theeee most important factor in tire wear is the amount of turns the tire has to make - and how severe the cornering is.

In order to generate the side force necessary to get the vehicle to change direction, the tire has to generate a slip angle. This causes the tire to slide relative to the road surface, which grinds off rubber - and the higher the cornering force, the greater the slip angle, and the faster the wear.

By contrast, driving straight ahead is practically free. Most folks don't have much of a choice about the routes they take and where they drive, but the do have a choice about of cornering severity, so in most respects, this can't be controlled by the driver.

Similarly, a tire's alignment can also generate a slip angle - that is, toe. Camber doesn't play much of a role in tire wear except for uneven wear - and the affect camber has is multiplied by how far off the toe is.

Road surface also is a major factor. Some locales have pretty abrasive surfaces - southern Florida for example. Again, most folks don't have much of a choice here.

Yes, stressing the tires with "jackrabbit starts" and severe braking will cause tires to wear more rapidly.

(Notice I am NOT discussing the tires themselves.)

The above is pretty much in order as I see it. Operating temperature is probably next - with the same thought: Most folks don't have much control of the ambient conditions. To put this in context, it takes a while for a tire to get up to operating temperature - and it takes a while for a tire to cool down - due to the insulating properties of rubber. And the affect of temperature is probably 10% of the affect of cornering. So I just don't see this area being worth the trouble of trying to control. I think we are talking about only a couple thousand miles difference in the life of a 60K tire.

Quote:
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.......As far as F1, they have both problems you mentioned. Getting heat into AND out of the tires. During the first laps the tires are too cold even with tire warmers, then later the tires are too hot and that heat causes the tires to break down. It was the too much heat part that Ferrari was working on. Here is what their results were, supposedly. I think all this info came from the italian court case vs McLaren, and the court released a PDF with the technical info blacked out, but of course they did it wrong and a non adobe pdf app could unblock the info and voila, it was public.

[[There was a quote in here that made some claims about the amount of improvement in performance using the gas mixture - and GTR comments below about that.]]

That is a ridiculous improvement. They were using the wheel as a heat dissipating radiator to increase tire life......
I'm struggling trying to understand the magnitude of performance improvement. I have no doubt that an F1 team would have enough resources to find very unusual sources of improvements - and that would include the tire inflation medium. And I have no doubt that they could utilize those improvements.

But where I am struggling is that it can make that much difference. If taking the heat away is such an advantage, then the heating up portion of the heat cycle would be negatively affected and it would take longer for the tire to reach a good operating temperature.

Also, I just can't see that taking heat away could extend the life of the tire that much. The tire has to get up to an operating temperature - which means the heat being generated by the tire is greater than the amount being taken away. The temperature will continue to rise after it reaches operating temperature, but it slows as it gets closer to the equilibrium temperature (the mathematical term is "asymptotic".)

I wonder if they were including the amount of time a pitstop for tires was taking - and that is why the numbers were so high. Turning a race from a 3 stop to a 2 stop is an enormous advantage.

Quote:
Originally Posted by GTR View Post
.......edit: wanted to add that the author for racecar engineering was wrong about the "specifically formulated for race cars" the gas was just 50% standard r404 refrigerant and 50% CO2.
I suppose that "specifically formulated" could cover ordinary materials mixed in a special way - especially if there doesn't seem to be any particular application other than that. I wouldn't be too harsh on the author even if he is exaggerating in order to make a point.
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Old 04-18-2014, 10:23 PM   #118 (permalink)
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R-404a will be a lot cheaper than helium and leak out a lot slower too.
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Old 04-19-2014, 12:46 PM   #119 (permalink)
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Quote:
Originally Posted by GTR View Post
So, seriously, unicorn corral? If every auto manufacturer started filling tires with N2 tomorrow, imagine how much fuel that would save over the years, how much tire wear it would reduce, and how much safer people would be. Less blowouts, for example.

All that benefit just from the simple fact that N2 molecules are bigger than O2 and leak out slower.
If you read the original post you will see why this unicorn excretion.

1, if you dont get the nitrogen fill for free like when you buy a set of tires they charge you $20 or more.
2, the nitrogen tire pushing web sites claim an you will receive an instant 20% increase in fuel economy.
3 the nitrogen tire pusher sites claim nitrogen defies the laws of physics by being unable to leak through rubber and that it doesnt change pressure at different temperatures.
4 The worst and most dangerous of all the nitrogen tire pushers sell false sense of security by making it seem like nitrogen tires do not require pressure checks.

That is why it is in the corral. Because its being sold by some as a magic bullet..
Now if you took a statistical sample size of vehicles, say a few thousand compared a group with nitrogen tires to a group with air, yes I bet you could see a slight fuel economy improvement and over all reduction in the number of tire failures with the nitrogen group.
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Old 04-19-2014, 12:58 PM   #120 (permalink)
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Quote:
Originally Posted by RedDevil View Post
Like I promised I tested the air in my tires.

When I bought one and a half year ago I raised the pressure to about 42 PSI. Kept checking and occasionally adding a bit to compensate for lost pressure.

Today I took a small plastic bag, a long nozzled gas lighter, a tiny stick and a rubber band and went testing.

First test, filled the bag with air from inside the house. Put the lighter in, ignited it, burnt fine for 7 seconds. Cut the flame when the bag began to wrinkle.

Second test, filled the bag with air from the tire (tripped the valve with the stick inside the bag). The lighter would not light. I coud see it spark, but it refused to flame even once. There was not enough oxygen to cause any kind of reaction.
Smelled the air from the bag as I let it out, smelled like rubber and unburnt lighter gas as expected, nothing else.

Third test, lighter in open air. Fired up fine, as expected.

Fourth test, held my breath for some time and then blew up the bag. Put the lighter in. Fired up just like in the other pure air tests, even though there must have been less oxygen in the bag.

So, I have only put air into the tires, quite some over time.
I am not the first owner though, they may have been filled with nitrogen initially, but I doubt it. The first year the tire pressure did drop off gradually in all four tires; this effect diminished over time to almost none now.

What is certain is that there is not enough oxygen in the tires to make a flame burn, while that flame does burn quite normally in slightly oxygen deprived (exhaled) air.
So the air in the tires has lost a substantial amount of oxygen.

The fact that the rate of pressure decline went down noticeably over time also confirms that nitrogen does in fact seep out less easily.
I did not expect that.
Myth confirmed, I guess.

So, apparently there is a benefit from filling tires with "nitrogen enriched" (oxygen depleted) air. They will keep their pressure better than tires filled with plain air, as those will lose most of their oxygen.
Having said that, you will need to keep an eye on the tire pressure regularly regardless of what they are filled up with, and in the end you will end up with almost pure nitrogen anyway.
You will just need slightly more air than if you use pure nitrogen.

As for better ride quality etc; obviously even if it does make a difference it is hardly an issue as the oxygen will get lost anyway.
After having access to an oxygen meter for confined space workers I was able to determine that for my self if I breathed normally over the sample probe I was consuming between 3% and 5% of the oxygen at sea level.
If I held my breath for between 90 seconds and 2 minutes I could consume up to 18% of the oxygen. Even after only 90 seconds I found that I used up 15 to 16% of the oxygen.
I blew a 0% oxygen content once, but trust me you dont want to go that far.

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