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Nitrogen use

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I know this has been bandied about considerably but many of you, especially those of you with advanced setups have progressed to the point where you really should be using nitrogen in your tires. Without getting into specifics I can tell you the expansion rates of nitrogen over humid air is incredible.
The main purpose of using nitrogen is consistency. Running later in the day when the track temp is hotter is when nitrogen will pay dividends. The difference in air vs nitrogen can be as much as 5-6 pounds and if you're running on the ragged edge of your tire's pressure limits this can be important. I realize that having a nitrogen bottle around can be a pain but if you have 2 sets of tires for race day then fill both up at your house and then find a larger air tank and fill that for making up pressure at the track.
Again the only thing you have in contact with the track is those 4 contact patches and that's where you need a lot of consistency, which is the main benefit of nitrogen.
 

Tucson 302

2013 Black LS #439
blacksheep-1 said:
I know this has been bandied about considerably but many of you, especially those of you with advanced setups have progressed to the point where you really should be using nitrogen in your tires. Without getting into specifics I can tell you the expansion rates of nitrogen over humid air is incredible.
The main purpose of using nitrogen is consistency. Running later in the day when the track temp is hotter is when nitrogen will pay dividends. The difference in air vs nitrogen can be as much as 5-6 pounds and if you're running on the ragged edge of your tire's pressure limits this can be important. I realize that having a nitrogen bottle around can be a pain but if you have 2 sets of tires for race day then fill both up at your house and then find a larger air tank and fill that for making up pressure at the track.
Again the only thing you have in contact with the track is those 4 contact patches and that's where you need a lot of consistency, which is the main benefit of nitrogen.

Where does the average Joe get nitrogen? Not something I have seen before
 
Any welding supply store usually has nitrogen. You can lease or buy the tank. I have a 20 yr lease and it costs $25 to exchange for a full tank each time. Found it easier to lease then buy. If buy have to get the tank recertified at certain time intervals that could be costly, if lease they take care of it.
 
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Best example I could find. It's pretty normal to see 200 degrees at the tires cords so you can see the effect of nitrogen at this temp. Deviations of this amount of pressure can wreak havoc on the car's setup. As an example, if one side of the car runs at..180 degrees and the other at 210 the difference is roughly 6 psi compared to 2, if you are attempting to run the same psi all the way around you will find it much more difficult to do with air. If you are running at max recommended tire psi there is a lot of leeway to be gained by running nitrogen.

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OK Rob.... bit the bullet and filled my tires with nitrogen today in preparation for this weekend at Barber. Also, filled a 5 gal tank to take to the track. 5 gal doesn't seem like much, but I hope it is enough to adjust pressure at track.

In previous track sessions (using air) I saw between 5 and 8 PSI increase from beginning to end of session -- most often 6 or 7. I shoot for 40 PSI hot and often need to bleed a little off as the day goes on. Do you know why that would be (track temp going up or ...)?

The real question is:
How much PSI increase can I expect to see using nitrogen?

Thanks.
-- Jim
 
Can you put nitrogen in a regular aluminum air tank? I don't think you can but thought I'd ask. There is an Airgas location close to me that will rent the bottle and refill. Maybe I'll go that route.
 
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When you hit your desired hot pressure then don't bleed anymore off, then for the next day, after the tires cool down you will have a new baseline (cold) pressure to start out with. I like to set all my pressures in the morning, all of them, then just monitor them as the day goes on correlating tire temperature with tire pressure. (I use 85 degrees as my "norm" because it seems like over 50% of the time when we go out the temp is around 85 degrees) As far as the pressure creeping up it could easily be track temp, air temp, the expansion of humidity within the tire or just the air in the tire expanding. Normally if you see inconsistent tire pressures or a spiking of one or more it's a humidity issue. We don't run the same pressures all the way around, but that being said we strive to have the fronts at a specific hot pressure and the rears at a specific hot pressure, identical from side to side, and no matter how many right or left hand turns there are. If they are within 1 psi of each other we call that good, if they are within 1 psi and are at the desired (predicted) hot pressure then that's real good.
So if you keep notes you should already know about where your cold starting pressures are to achieve the desired hot pressure, assuming that nitrogen will not expand as much as air, I'd put an extra pound or 3 in the tire in the morning and run the first session, bring the car in hot and recheck the psi, it should be close to what you want, if not add or subtract whatever is needed to get there, run the next session and recheck. I know you guys don't have a tire pyrometer, but you might want to invest in one of those laser temp gauges, measure the tire temp on the sidewall in the location of the valve stem (for consistency) and work your numbers from there. Remember that once a tire is run it will never get back to ambient temperature until the next day, so you are always working with hot psi numbers after the car starts.
One of the tricks I use is to get a discarded tire/wheel and put the desired amount of nitrogen in it, then, during the day, I monitor the rise in temperature and check the psi, essentially creating a graph based on ambient temperatures. In this manner I can back up my math as the day goes on, knowing that if we go to a sticker set of tires it will need to be "X" psi because the day has gotten hotter, but again, once thos etires go on the car, you are now working hot pressures only.
 

Grant 302

basic and well known psychic
I use a 5 gal tank (air not N) for adjustments filled to about 70 psi. Usually lasts me the day of adjustments plus topping off for my 'street' pressures on the way home. I usually also overfill any spares so I have a little extra if need be.

With Rob's advice regarding tire pressures, I have gotten to where I could have everything set where there are often no adjustments needed in the first two sessions and only make adjustments for the SoCal mid day and afternoon temps. Making a chart for your tires is priceless for getting started at different temps. I go more often in the fall and winter and knowing how to set pressures when your day starts in the 30s or 40s to saves precious seat time...and is just safer.

A lot of his tire pressure advice is in the old 'advanced setup' thread.
 
Thanks guys. Rob, I have measured the tire pressure stone cold the morning after a track day and it is consistantly 32 or 33 PSI. But, I generally start with a little more than that because here (like where Grant is) mornings are usually much cooler than the afternoon and it is easier to bleed a bit off than to add.

So... as Ron suggests I will add 3 PSI to the usual 32 and start the day with a stone cold 35 PSI nitrogen and adjust as necessary hot. Hopefully, any adjustments will be much smaller with the nitrogen.
 
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YellowJacketBoss302 said:
Thanks guys. Rob, I have measured the tire pressure stone cold the morning after a track day and it is consistantly 32 or 33 PSI. But, I generally start with a little more than that because here (like where Grant is) mornings are usually much cooler than the afternoon and it is easier to bleed a bit off than to add.

So... as Ron suggests I will add 3 PSI to the usual 32 and start the day with a stone cold 35 PSI nitrogen and adjust as necessary hot. Hopefully, any adjustments will be much smaller with the nitrogen.

You drop pressure the colder it gets..srsly, trust me on this, look at your first paragraph and think about it for a second. 32 psi at say..40 degrees is the same as say..40 psi at 95 degrees, set the pressures just once, then monitor them, you only change them when you want to do a tuning change. Look up that "advanced setup" thread. If you keep playing with tire pressures you will adjust yourself right out of the ballpark.
 

ArizonaBOSS

Because racecar.
Moderator
8,730
2,734
Arizona, USA
After reading various blacksheep threads here, I set my tire pressures very early in the AM (pretty much as soon as I wake up), and keep them in the shade until ready for use. I don't bleed off any pressure all day unless the car has some handling quirk (none so far). Works great for me.

This is on "regular" air, not N2, strictly due to convenience factor/laziness.

Note: This only really works if you have known good tire pressures going in. If you're still experimenting, it's good practice but not necessarily going to find your optimal setup.
 
My Nitrogen test results:
I have measured tire pressure at the end of the last track session and again the next morning --cold in my garage -- on two separate days with AIR in the tires.
Did essentially the same this weekend with Nitrogen -- measured hot pressure at end of day 1, measured cold pressure in my garage at beginning of day 2, and measured hot at end of day 2 (having made NO adjustments).

The results opposite of what I expected.
Average pressure difference with AIR = 7.89 PSI
Average pressure difference with NITROGEN = 9.11 PSI

Since I understand and believe the graph Rob posted, I must conclude that the Nitrogen the tire store put in my tires was contaminated with moisture. I will try to get more information regarding the source and purity of the nitrogen the store uses.
 
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A couple of things come to mind, did you remove the air from the tire prior to installing the nitrogen? and yes, it could be impurities in the nitrogen. When you let air out of the tire (unless you have a way to completely evacuate the tire) try not to go below 15 psi .

Those numbers are a little disturbing actually.
 
The Nitrogen was put in the tires at a local tire store and I did not watch them do it. They understood that I wanted the air replaced with Nitrogen, but I can't swear that they actually did. I'm not disturbed yet, but I am very suspecious of the quality (specifically the dryness) of the gas they used.
 

Grant 302

basic and well known psychic
The temps and pressures need to be charted. Cold and hot temps are never the same. Biggest thing I learned from the other thread. Make a chart of the working temps and pressures. Otherwise the 'data' doesn't mean anything.
 

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