Nitrogen...

[Robert K.]

Re: Nitrogen...

1 ATTA BOY for Joe!

Leif,
keep your posts coming,

Take care,

[Jim L.]

Re: Nitrogen...

That's a big risk, Jim, what if the ideal gas law is repealed?

There would be an up side to the repeal.

As the law is written, I'm compelled to be concerned about the change in tire pressure with temperature. Since I'm not, I'm breaking the law. After the repeal, I'll be in the clear.

[John D.]

Re: Nitrogen...

That's a big risk, Jim, what if the ideal gas law is repealed?

Robert Boyle (1627-1691) would be turning in his grave...

[Michael W.]

Re: Nitrogen...

That's a big risk, Jim, what if the ideal gas law is repealed?

As a wise friend in FL likes to say about gravity, it's not just a good idea it's the LAW!

[Bill H.]

Re: Nitrogen...

I have a bit of experience using nitrogen in tires, 20+ years using it in race cars. I have a nitrogen tank in the race trailer. The important things mentioned here (for automotive use) were "commercial nitrogen is dried and has a low moisture content". by Duke and "air is 78 % nitrogen" by John.
The tires we run nitrogen in have the pressure checked 6-8 times per day.
The statement that nitrogen "maintains a steady PSI" is incorrect.
The statement that nitrogen won't leak is also incorrect.
The ONLY reason we run nitrogen is what Duke said - it's dry and has low moisture. What this provides is predictability in tire pressure increases as the tires warm up, nothing more. We can't get that predictability with compressed air even with a well maintained compressor. It's the moisture content in the gas that causes the deviations.
We need that predictability to get the correct tire temperatures across the tire as they get hot and the pressure increases. If you think nitrogen maintains a steady pressure, watch a NACSAR or Indy Car throw sparks on the track until the tire heats up and the tire pressure lifts the car up a bit.
And, If you put nitrogen in your street tires, did you evacuate all the moisture laden air out first ?(we do).
I see no good reason to run nitrogen in street tires unless you're going to the track.

[Michael W.]

Re: Nitrogen...

I have a bit of experience using nitrogen in tires, 20+ years using it in race cars. I have a nitrogen tank in the race trailer. The important things mentioned here (for automotive use) were "commercial nitrogen is dried and has a low moisture content". by Duke and "air is 78 % nitrogen" by John.
The tires we run nitrogen in have the pressure checked 6-8 times per day.
The statement that nitrogen "maintains a steady PSI" is incorrect.
The statement that nitrogen won't leak is also incorrect.
The ONLY reason we run nitrogen is what Duke said - it's dry and has low moisture. What this provides is predictability in tire pressure increases as the tires warm up, nothing more. We can't get that predictability with compressed air even with a well maintained compressor. It's the moisture content in the gas that causes the deviations.
We need that predictability to get the correct tire temperatures across the tire as they get hot and the pressure increases. If you think nitrogen maintains a steady pressure, watch a NACSAR or Indy Car throw sparks on the track until the tire heats up and the tire pressure lifts the car up a bit.
And, If you put nitrogen in your street tires, did you evacuate all the moisture laden air out first ?(we do).
I see no good reason to run nitrogen in street tires unless you're going to the track.

Thanks for your post. Very accurate and interesting info, in particular the comments about the predictability of pressure rise with temperature increase.

What many overlook or are not aware of is the tire pressure specs for street driven vehicles are to a certain degree 'reverse engineered' numbers. The OEM determines the optimum pressure that suits the average operating profile of the vehicle, a 'hot' pressure so to speak. It is also known that this pressure will decrease once the vehicle is stopped and allowed to sit for a while. It is this lesser cold pressure that we set our tires too, not the greater hot pressure.

If it was true that nitrogen expanded at a lower rate than air, the correct hot operating pressure would never be achieved, a potentially dangerous situation.



.

[Michael G.]

Re: Nitrogen...

Thanks for your post. Very accurate and interesting info, in particular the comments about the predictability of pressure rise with temperature increase.

What many overlook or are not aware of is the tire pressure specs for street driven vehicles are to a certain degree 'reverse engineered' numbers. The OEM determines the optimum pressure that suits the average operating profile of the vehicle, a 'hot' pressure so to speak. It is also known that this pressure will decrease once the vehicle is stopped and allowed to sit for a while. It is this lesser cold pressure that we set our tires too, not the greater hot pressure.

If it was true that nitrogen expanded at a lower rate than air, the correct hot operating pressure would never be achieved, a potentially dangerous situation.



.

Mike, I'm not sure "dangerous" is the best word here. Maybe "less than ideal" would be better. While there may be an optimum pressure, automotive specifications are written to include a range of acceptable values. Both the hot and cold pressure values are designed to be within this "acceptable" range.

[Michael W.]

Re: Nitrogen...

Mike, I'm not sure "dangerous" is the best word here. Maybe "less than ideal" would be better. While there may be an optimum pressure, automotive specifications are written to include a range of acceptable values. Both the hot and cold pressure values are designed to be within this "acceptable" range.

No, I chose the word 'dangerous' deliberately to illustrate the irrational theory used by the pro-nitrogen crowd. If nitrogen did expand at a lower rate as they claim, this would cause the tire to operate below the "acceptable" range of pressures.

[Jim L.]

Re: Nitrogen...

If nitrogen did expand at a lower rate as they claim, this would cause the tire to operate below the "acceptable" range of pressures.

Well that's just silly. If nitrogen were to behave like that, you would adjust the initial pressure to compensate. Simple.

[Dick W.]

Re: Nitrogen...

Well that's just silly. If nitrogen were to behave like that, you would adjust the initial pressure to compensate. Simple.

We were using pure nitrogen in NASCAR in the '60's. You pretty well knew what the pressure would be after 4-5 laps. No variables. With just O2, you could never know what the pressure would do. NASCAR teams use tire pressure today to fine tune suspension settings. Years ago the chassis was too limber and 2-3 # would make very little difference. Today 1/4 # makes a lot of difference.

[Michael W.]

Re: Nitrogen...

Well that's just silly. If nitrogen were to behave like that, you would adjust the initial pressure to compensate. Simple.

Of course it's silly- but there's no revised initial pressure given to consumers when they switch is there? The tires are inflated to the standard placard pressures and that's it it. Which means...........

[Dick W.]

Re: Nitrogen...

Next out of town trip I will compare pressure cold to one hour of driving

[Duke W.]

Re: Nitrogen...

On racetracks I start out with 36 psi cold on summer high perf or DOT legal racing tires, all H and above radials. After a twenty minute hot lap session in warm to hot ambient temperatures the pressure rises by 8-10 psi.

Highway driving in the same conditions yields about 4-5 psi increase.

Duke

[Jim L.]

Re: Nitrogen...

On racetracks I start out with 36 psi cold on summer high perf or DOT legal racing tires, all H and above radials.

Those must be radials.

In vintage, where we race on bias ply tires, I get my best grip with cold pressures of 23 psi front, 21 psi rear. I have no idea what the hot pressure becomes

[Bill H.]

Re: Nitrogen...

Geeze, you guys run a lota air. I start out at 10 & 12 on my can and 14 & 16 on the car in my avatar.

Actually, our cold temps are set by first measuring the track temp then, going to the log book to see what we ran at that temp the last time. A 60 degree track temp in the a.m. at Laguna will be different from 100 degrees at lunch time. The final pressure is determined by in after 15 minutes on track in the practice session and taking 12 tire temperature readings.