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Nitrogen and Cup 2 tire pressures on track

pilotgore

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Has anyone run nitrogen in their tires on track, and if so what kind of pressure variation have you experienced hot vs cold? I’ve read a few places where people mention a 2 psi hot temp increase with nitrogen vs 8 psi with standard compressed air.

For background, I have a ‘19, non R with stock cup 2’s. I typically follow the manuals recommendation on track and start out 28 cold. I’ve then been aiming for around 36 hot on all 4 corners, or 36 front and 34 rear (instead of 38 front 36 rear per the manual.). I think I started doing this after I noticed better lap times during a session with lower pressure (which could have been a coincidence) and I’ve been using lower pressures ever sense. Does anyone have any recommendations?

It just struck me a few days ago that I have access to free bottled nitrogen and should probably be running nitrogen for track duty. I plan to deflate then inflate the tires three times with nitrogen to try and remove as much non-nitrogen as possible. Also, I’ll have a 10 gal 220psi tank I’ll take to the track with me for top ups.

Any recommendations or any tidbits of personal experience would be greatly appreciated (especially as it relates to our cars and the cups 2’s)

Thanks!
 

honeybadger

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I haven't run nitrogen because I've been told it slowly leaks. NOt much to add there from me. Sorry.

I did want to reply and recommend never running them more than 34 hot. My typical routine is to watch pressures during the session and see if they go above 34. If they do, I let out however much is needed to get them back down to 34 or lower. At COTA in the warmer months, this can mean starting out at 20-22 cold depending on the tire.
 

pilotgore

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I haven't run nitrogen because I've been told it slowly leaks. NOt much to add there from me. Sorry.

I did want to reply and recommend never running them more than 34 hot. My typical routine is to watch pressures during the session and see if they go above 34. If they do, I let out however much is needed to get them back down to 34 or lower. At COTA in the warmer months, this can mean starting out at 20-22 cold depending on the tire.
Thanks for the bit about tire pressure, that’s good to know. I’ll use 34 this weekend and see how it goes.
 

jmn444

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I haven't run nitrogen because I've been told it slowly leaks. NOt much to add there from me. Sorry.

I did want to reply and recommend never running them more than 34 hot. My typical routine is to watch pressures during the session and see if they go above 34. If they do, I let out however much is needed to get them back down to 34 or lower. At COTA in the warmer months, this can mean starting out at 20-22 cold depending on the tire.
just cup 2's or pretty much any tire?
 

Flyhalf

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34 is an happy spot for our cars.

A note
Nitrogen. Some people swear it is better. Some people say useless.
Some fact

The common air is made with...78% of nitrogen..
Not much difference.
Full nitrogen could ,in theory , absorb less umidity for a better temp managment. We are talking about smaaall details.
Keep in mind that if you drive to the track and you bring your pressure to 28..you will need to add air to drive back home to avoid to ruin the tires.
In other words the effort is not worth it.
Alex
 

honeybadger

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just cup 2's or pretty much any tire?
Depends a bit on the tire. But we're talking 32-34. I;ve found the Pirellis and Hoosiers like 32ish for grip (probably sacrificing longevity a bit). All the street tires I've run like 34. Really have to use a pyrometer to fully dial it in, though.
 

Flyhalf

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Depends a bit on the tire. But we're talking 32-34. I;ve found the Pirellis and Hoosiers like 32ish for grip (probably sacrificing longevity a bit). All the street tires I've run like 34. Really have to use a pyrometer to fully dial it in, though.
Agreed.
I tried. 3R (the best) A052. NITTO NT01. CUP2. 4S. HOOSIER (32psi actually) .all where top speed at 34psi. At 36 i was 1sec slower. Same at 31.
 

Tomster

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The difference is dryness. It is the water in the air that causes wider pressure fluctuations. So, theoretically, dry air should be about the same as nitrogen. I have toyed with the idea of running with it because of the larger fluctuations I see at my track. In fact, due to the roval nature of the course, it is recommended by Michelin engineers to run much higher pressures as stated. So each track varies with pressure requirements.
 

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Mach4.6

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I run nitrogen in my tires, I fill and drain them 3 times to get the air out, I'll still see about 5-6 lbs increase in pressure once the tires are hot. I don't notice any leaking but then again I change my tires pretty often. I just ordered some Forgelines and added a second valve stem port to bleed all the air out.
 

dpAtlanta

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I was told by a Lockheed Design Engineer (Ph.D, PE) that aircraft uses Nitrogen because it's inert, and if the plane has to belly land, they don't want any oxygen in the tires because oxygen is fuel.
 

Flyhalf

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I was told by a Lockheed Design Engineer (Ph.D, PE) that aircraft uses Nitrogen because it's inert, and if the plane has to belly land, they don't want any oxygen in the tires because oxygen is fuel.
Yeah not really to disagree..but if the plane belly land..the tires are not out ..lol
By the joke
Different situation :)
 

meterman

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I agree on the 34 as max on the track. I've gone through 4 sets of Cup 2's this year and I used the recommended air pressures and found the center of the tire really started chunking and when I dropped the pressures down on the next set it really helped. I start at 26 front and 28 rear. As soon as I get off the track I make sure the let out pressures to get back to 34.
 

Arknsawchuck

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I was told by a Lockheed Design Engineer (Ph.D, PE) that aircraft uses Nitrogen because it's inert, and if the plane has to belly land, they don't want any oxygen in the tires because oxygen is fuel.
I crewed the Lockheed C-130 acft for 30 years and we used air for a long time. Then in the late 90s we went to nitrogen. We were told it was due to temp variations at altitude vs ground. Saw a lot of tires blow over the years and other than destroying sheet metal it never cause any fires or such. Not to say that under the right conditions it wouldn't.
 

dpAtlanta

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Ph.D does stand for "Piled Higher & Deeper", so maybe he was not correct?
I did start the post with "I was told..."; you would obviously have more direct knowledge than I about the Lockheed aircraft.
Interesting stuff!
 
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