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Thread: Nitrogen

  1. #1
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    Nitrogen

    Who is using it on their track cars?

    How do you like it?

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    IN tires, or in dampers? Or for ait tools?

    Assuming you mean tires, it's really just a matter of a smaller window in PSI gain ... Being a smaller change, the percentages are lower, and in theory it's easier to hit the sweet spot. For us, the hassle is certainly not worth it. To really do it right, you need 2 valves in a wheel, and you suck out air with one, then fill with N in the other. Ain't nobody got time for that. I suppose just filling with N without a second valve would work somewhat. If your tires gain say 8 PSI with air, they might gain say 4-5 with N.

    If you already know how much PSI gain you will get using pain old air, then it's sort of pointless ... certainly for the trouble.

    Now having said all that, the one benefit might be if your race specifically on Pirelli 17" 245s. The sidewall on those explode below ~25psi, but they perform best at 29-30 hot ... so when using Air (and starting at 21psi), you need to be REALLY careful until the PSI gets up there. With N, we could start at say 26 psi, and probably be ok.
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  3. #3
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    Well, to be more specific -- TIRES.

    Specific use is track days, TNiA, and SCCA Time Trials. So, everything centers around 20 minute segments. Track days and TNiA events are about working on skills while using a Catalyst, but TT is actual competition. The conventional wisdom for TTs is warm up lap, green flag and in the next couple laps one will likely have the best combo of tread temps and internal pressures for a competitive lap followed by backing off (to try to stabilize and cool the tires a bit), and then go for another burner lap. When I started competing in TTs, I saw the wisdom of that. Another dynamic I came to understand that tire temps and pressures changed less as the tires were accumulating laps over the spread of various events.

    My goal is to have more laps available at optimum(ish) pressures to maximum the number of competition laps among the 7-10 competition laps in each 20 minute TT session. If I was road racing, obviously I would be chasing the best pressures for long runs.

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    I use it simply for the convenience, in that I have 2200 psi of gas sitting in my trailer.
    Doing it right is a complete PITA as Scotch pointed out.

    If you have an easy way to transport it its an easy vessel that can handle tire top offs / filling, provide some bursts on air tools if needed and if you have such things operate your air jacks.
    If I didnt need it for two of the three above things I'd just carry a simple air tank for tire top offs.
    I would put myself in the not worth it camp.

    Keep in mind that tire pressure in modern radial racing tires adjusts the spring rate of the tire, it doesnt do anything for contact patch or heat management.
    Pressure = spring rate
    Alignment = contact patch
    Your Right Foot & Hands = how much heat you put in it
    Last edited by jimmypet; 10-25-2021 at 11:27 AM.
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    Tire nitrogen is a scam in the sense of paying a premium or expecting something better to happen. Water vapor is what causes excessively wild swings in pressure due to temperature. All the gas in 'air' follows the ideal gas law the same as pure nitrogen.

    Dry compressed air gets you to the same place, and if you don't have a dryer on your air compressor, shame :P

  6. #6
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    Quote Originally Posted by BrianSalo View Post
    Tire nitrogen is a scam in the sense of paying a premium or expecting something better to happen. Water vapor is what causes excessively wild swings in pressure due to temperature. All the gas in 'air' follows the ideal gas law the same as pure nitrogen.

    Dry compressed air gets you to the same place, and if you don't have a dryer on your air compressor, shame :P
    A drier on an air compressor does not scrub enough moisture to make air "dry" enough to be resist temp changes -- at least in the KC area. If it was Arizona, that might be different.

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    Water vapor is a gas.

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    Quote Originally Posted by aeronaut View Post
    Water vapor is a gas.
    Yes. And???

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    jimmypet ...
    "Keep in mind that tire pressure in modern radial racing tires adjusts the spring rate of the tire, it doesnt do anything for contact patch or heat management."

    If that is true, why do surface temps change dependent on tire pressure? Why does the outside of a tire wear heavily when under-inflated? Why do over-inflated tires show higher temps in the middle of the tread? And even if your statement is true, the tire's inherent rate will change as pressures change (increase) due to heat build up.



  10. #10
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    Quote Originally Posted by snaponbob View Post
    jimmypet ...
    "Keep in mind that tire pressure in modern radial racing tires adjusts the spring rate of the tire, it doesnt do anything for contact patch or heat management."

    If that is true, why do surface temps change dependent on tire pressure? Why does the outside of a tire wear heavily when under-inflated? Why do over-inflated tires show higher temps in the middle of the tread? And even if your statement is true, the tire's inherent rate will change as pressures change (increase) due to heat build up.
    I race on Hoosier radial slicks, I bought a set of R7 DOT Hoosiers to run an SCCA Majors race in another class that required DOT tires.
    I called the Hoosier techs who have always been SUPER helpful for some pressure advice.
    This is paraphrased from one of the Hoosier guys.
    He told me that all us racers need to stop thinking of modern racing radials as we thought of old bias ply tires in the 60s and 70s.
    He said manipulation of the air pressure manipulates the spring rate of the tire.
    We could inflate the a modern Hoosier radial by 20-30 psi difference and not change the contact patch.
    We would change the spring rate, which would / could drastically alter the way the car handles because its made the tire much stiffer (or softer) like adding (or subtracting) hundreds of lbs of spring rate but we will not "balloon" the tire.
    He went on to say I can put anything between 25psi to 45psi into my tires (the slicks or DOTs). He said use the pressure that makes the car feel best (hence fastest) for me & my setup.
    He also said he has top tier drivers on Runoffs podiums that use the same exact tires at both ends of the pressure spectrum some in the mid 20s some nearing upper 40s, they use what makes it fastest for their individual setup.
    So the hot pressure should be what makes your car handle the best for your setup (combined with your alignment, etc).

    Thats what he told me and I've followed that advice ever since.
    Take that for what its worth, a bunch of words typed by some guy you dont know on the internet.

    So the Nitrogen advantage is simply allowing you to start closer to your optimum pressure.
    I dont think that is worth the PITA to do it the way you have to do it like Scotch described.
    Last edited by jimmypet; 10-25-2021 at 10:48 PM.
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  11. #11
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    Quote Originally Posted by snaponbob View Post
    Yes. And???
    That should have been in the form of a question. In that, if water vapor is a gas that obeys the same ideal gas law that N2 and air do, then how do any of those change the temperature vs pressure curve of a tire?

    - - - Updated - - -

    Quote Originally Posted by jimmypet View Post
    I race on Hoosier radial slicks, I bought a set of R7 DOT Hoosiers to run an SCCA Majors race in another class that required DOT tires.
    I called the Hoosier techs who have always been SUPER helpful for some pressure advice.
    This is paraphrased from one of the Hoosier guys.
    He told me that all us racers need to stop thinking of modern racing radials as we thought of old bias ply tires in the 60s and 70s.
    He said manipulation of the air pressure manipulates the spring rate of the tire.
    We could inflate the a modern Hoosier radial by 20-30 psi difference and not change the contact patch.
    We would change the spring rate, which would / could drastically alter the way the car handles because its made the tire much stiffer (or softer) like adding (or subtracting) hundreds of lbs of spring rate but we will not "balloon" the tire.
    He went on to say I can put anything between 25psi to 45psi into my tires (the slicks or DOTs). He said use the pressure that makes the car feel best (hence fastest) for me & my setup.
    He also said he has top tier drivers on Runoffs podiums that use the same exact tires at both ends of the pressure spectrum some in the mid 20s some nearing upper 40s, they use what makes it fastest for their individual setup.
    So the hot pressure should be what makes your car handle the best for your setup (combined with your alignment, etc).

    Thats what he told me and I've followed that advice ever since.
    Take that for what its worth, a bunch of words typed by some guy you dont know on the internet.

    So the Nitrogen advantage is simply allowing you to start closer to your optimum pressure.
    I dont think that is worth the PITA to do it the way you have to do it like Scotch described.
    Good stuff!

  12. #12
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    Well, now I am going to cause furniture to be thrown !!

    I started autocrossing in 1981. (If I knew THEN what I know now.) Hoosiers back then were bias ply tires that were made of tissue paper and has black stuff sprayed on it. Competitors at the pointy end of the stick that DID use them in stock classes usually had them only at Nationals, and normally had TWO sets. Why? They could/would cord after three runs. Over time they evolved in A6s and R6s in to the "DOT approved" (laughable then and still laughable now) versions. In road racing the A6s were qualifying or SHORT sprint (cooler weather) tires and the R7s were for longer sprints. About a decade ago SCCA changed the stock classes to 200TW. And because the government wrote tire wear ratings in such as way that manufactures were tasked with enforcing the wear specs themselves. Over time, the 200tw wars provided tires that gripped, wore, and heat cycled like A6s. Further, as track driving became more and more popular, a lot of new drivers plus more and more autocrossers were going to 200TW tires. BUT, what was best for Solo was NOT necessarily viable for track days or Time Trials due to wear issues. So, now there are 200TW tires that are best for Solo and others are best for track use, and even the track choices are widely varied in how they work.

    But one constant has been tire pressure to maximize whatever tire is being used in either track or Solo use. I can't remember all the brands of tires I have used, but once I moved to the KC area 17 years ago my Solo game changed. I started using A6s is Stock class Solo, then in Street Prepared. I changed cars and went to what was legal in the classes I was in, and BFG Rivals or Bridgestone RE71s were the best tires. Three seasons ago I migrated to track driving. How tires are used and managed in Solo vs track are vastly different. But, the common thread in managing tires was managing pressures.

    All that said, I understand that tire pressure DOES impact the effective "spring rate" of tires, but (short of NASCAR and F1) cars are set up with springs, dampers, sway bars, and alignment. So, now we get to the topic at hand --- what's inside the tire.

    "Keep in mind that tire pressure in modern radial racing tires adjusts the spring rate of the tire, it doesn't do anything for contact patch or heat management." Now, the furniture will fly. A pyrometer will completely disprove the back half of that statement. Will pressure impact spring rate? Not enough to negate the need to have a proper spring package on a car before anything else is done. As for managing tire pressures for best contact patch, it's VERY important. In EVERY instance too much pressure will distort the middle of ANY radial ply tire, regardless of the material the radial belt. I have seen it on Rivals, Re71s, RS4s and the stiffest tire on the market, RT660s. Too much pressure will show increased temps in the middle of the tire's contact patch, and too little will show center temps lower than outside temps.

    Now, we get to my specific needs. My "world" is centered on 20 minute sessions separated by 40-60 minute breaks. I have for YEARS pre-warmed the wheel/tire assemblies by dragging my brakes at low speeds to heat up the rims. Obviously, that will pre-heat the air in the tires. In autocross that helps a LOT because an 10-15 psi pressure increase in pressures across a 45-75 second run make for some difficult driving. In track use, I have found what others (better than me) have said to be dead accurate -- ones best times will come around lap 3-4 and or 6-8. Why? Pressure gains. They have said that the tires will be at there best on those laps, and the in between laps are used to cool the tires and position yourself in the field of cars to have clear track (ala F1 qualifying). How does this apply to longer stints like road racing stints? NOTHING !!!! Tire pressures are set in such a manner that after a handful of laps the tire the tires are up to temp and pressure.

    With that as a preface, my thoughts about nitrogen is to smooth and minimize pressure changes in order to have more predictable tire performance during 15(ish) minutes of a 20 minute session. As for tire spring rate, I will defer to folks like Ross Bentley for guidance. And I have yet to read or hear his words about tire pressure not changing contact patches. So, my choices are 1) just deal with humidity ladened air, 2) use 100% dry air, or 3) 95%+ nitrogen filled tires. So, #1 is a no brainer, as I waste a few laps in every session, #2 is just not practical, and #3 nitrogen. With nitrogen, if I can have over 90% N, that should slow the pressure changes. The tires can be prefilled at home, and I can carry a modest sized high pressure tank to tweak the pressures at the track.

    Again, if I was road racing, this entire conversation would be moot. Just find the proper pressures during practice session, and that's pretty much that.

  13. #13
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    Great discussion. Tires are hard. I've learned a lot over the last 2 years digging deep and listening to the small percentage of folks that actually know, or measure.
    For example, increasing pressure increases tread temperatures.

    I *think* what I hear the Hoosier guy saying is, race tires are semi-rigid (far from a balloon). The change in spring rate must be considered, and can be taken advantage of, within the small-ish window of air pressures used on track. Also, because the tires are semi-rigid, they do not follow the balloon physics of "contact patch size is proportional to pressure and weight of vehicle" formula.

    Oh to have a beer with a goodyear race tire engineer.

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    Quote Originally Posted by snaponbob View Post
    Again, if I was road racing, this entire conversation would be moot. Just find the proper pressures during practice session, and that's pretty much that. [/COLOR]
    This pretty much sums up our experience. I admit to knowing nothing about autox. I did do some solo sprint (TA) stuff years ago, but was far from top of field to know enough about tire management
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    Quote Originally Posted by aeronaut View Post
    Great discussion. Tires are hard. I've learned a lot over the last 2 years digging deep and listening to the small percentage of folks that actually know, or measure.
    For example, increasing pressure increases tread temperatures.

    I *think* what I hear the Hoosier guy saying is, race tires are semi-rigid (far from a balloon). The change in spring rate must be considered, and can be taken advantage of, within the small-ish window of air pressures used on track. Also, because the tires are semi-rigid, they do not follow the balloon physics of "contact patch size is proportional to pressure and weight of vehicle" formula.

    Oh to have a beer with a goodyear race tire engineer.
    SO much depends on a specific car's setup. I have an 04 M3 with no aero and a 750/850 spring package. As spring rates go up, the effective "spring rate" of tires can start to matter. NASCAR is a classic example of using air pressure to change vehicle dynamics, but most of it was to do with "wedge" on circle tracks. When those cars are running on road courses, more conventional aspects of tuning come into place as they are far less likely to use wacky pressures to make them turn. (Example is that on short oval tracks the left fronts can be running at 10 psi and HUGE positive camber.) Getting back to "normal" race cars, non-aero M3s may be running 1000 pound springs on smooth tracks, and with aero even more. So, as suspension compliance declines, tire compliance can become more and more important. Further complicating things is what sort of racing one is doing.

    Bottom line ------------------------- "it depends".

    - - - Updated - - -

    Still wish someone who has used nitrogen would join in.

  16. #16
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    Quote Originally Posted by aeronaut View Post
    Water vapor is a gas.
    Unless it condenses into liquid, vastly changing the mass of gas inside the tire.
    Last edited by BrianSalo; 10-26-2021 at 05:47 PM. Reason: type-O

  17. #17
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    Quote Originally Posted by BrianSalo View Post
    Unless it condenses into liquid, vastly changing the mass of gas inside the tire.
    Do you really think that's possible, considering how physics in this universe works?

    I see what you mean ... so the gas portion becomes smaller, while the liquid portion is larger ...
    Last edited by ScotcH; 10-26-2021 at 10:11 PM.
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    Just my two cent from experience. I bought a tank for my trailer for convenience then really wanted to know if nitrogen made any difference in PSI gains on the track. Thinking there is always some regular air left over in even a flat tire I picked up a vacuum pump and completely deflated a set of tires. Pretty interesting to see how the tires collapsed on the rims under vacuum. They were then reinflated with pure nitrogen. The tires heated up exactly the same on the track as with air. not sure about the physics or the dryness factor but I'm pretty sure from this experience the difference is negligible.

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