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STAYFILL: Stay Harder Longer (your tires I mean)

Discussion in 'Fred's House of Pancakes' started by wjtracy, May 28, 2015.

  1. wjtracy

    wjtracy Senior Member

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    Hey don't shoot the messsenger, "stay harder longer" is the official slogan of this stuff.

    INFO: Click on About Stayfill

    We've discussed ad nauseum that Nitrogen (N2) is a relatively big molecule, among the slowest gases to leak thru the rubber of a tire. Thankfully since air is 79% N2, you get most of the benefit of N2 just filling your tires with air. There is a minor advantage for 100% N2 if you want to do that, because Oxygen (O2) and many other gases leak about 3-4 times faster than N2.

    >>But is there any gas better than N2 that is practical to fill tires? Not much, but here's one option:

    STAYFILL for your bikes tires.
    It's expensive: $25 bucks for a small tube like CO2. The idea is: Fill it, and never fill again..it holds pressure. STAYFILL is a propietary gas mixture, apparently mostly trifluoro-iodo.methane (CF3I). They claim completely inert, safe, no ozone damage potential.

    [​IMG]

    Because it's so expensive, the applications are smaller tires: bike tires, NFL footballs (somebody should send TomB a sample), and so on.

    >>I asked STAYFILL if it could be safely used in a Prius spare tire inside the passenger air space. They said yes that would be OK. My spare was down to 20 psi (probably enriched with N2 since the O2 had probably leaked out). So I bumped it up to 35 psi with STAYFILL. That took about $20 bucks worth of STAYFILL, so then I took the spare to full pressure with air, not wanting to go broke. So now my spare has about 30% N2 + 25% STAYFILL+ 45% Air. Maybe last time I check it...should hold pressure OK.

    I used the same approach on my bike tires. Although STAYFILL recommends emptying out the air before filling, I assume the air left in the tire is N2-enriched, so I put the STAYFILL on top of that. Maybe 50% STAYFILL and the rest "stale" air.

    I see the spare tire a decent application (if it were cheaper).

    .
     
    #1 wjtracy, May 28, 2015
    Last edited: May 28, 2015
  2. JC91006

    JC91006 Senior Member

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    There's a mechanic down the street from me that has nitrogen for his customers that buy tires, I might ask him to fill ask my tires with that stuff
     
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    I wouldn't buy stock in this company. I use regular air on the car tires, and they hold pressure with monotonous consistency. Even the temp spare with 60 psi. Maybe once a year, twice at most, I actually have to intervene and add some.
     
  4. The Electric Me

    The Electric Me Go Speed Go!

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    Benefit vs. Cost.
    Doesn't seem worth it to me.

    Monitoring and keeping my tires filled with good ol' air, isn't that difficult to me, and as part of the whole automobile ritual of maintenance I use it as a chance to evaluate my tires as a whole. I guess I don't need to stay harder longer.
     
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  5. wjtracy

    wjtracy Senior Member

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    Well I know we got bikers and motorcyclists here, so keep that in mind (and Patriots fans)
     
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  6. bisco

    bisco cookie crumbler

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    maybe they'll make a deal with roger goodell.:cool:
     
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Over repeated fillings with 79%/21% N{2}/O{2}, the higher leakage rate of O{2} will 'enrich' the remaing N{2}/O{2} ratio. The tire will approach 100% N{2} about the time the tread is gone. So if you partially inflate the new tire with the old tire air . . .

    Bob Wilson
     
  8. wjtracy

    wjtracy Senior Member

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    To me N2 makes pretty good sense for new tires as per Costco practice. Then I would just top off with air. Might be really good to fill that spare with N2 though since I tend to not check it.

    ...probably not 100% N2 probably old tire probably goes to around 93% N2 when the O2 partial pessure inside the tire is equal to the O2 partial pressue in the air. Also it takes several years to get there.
     
    #8 wjtracy, May 28, 2015
    Last edited: May 28, 2015
  9. tochatihu

    tochatihu Senior Member

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    Data are not readily available for CF3I, but I reckon it is larger than the following. Biggest to smallest: CO2, N2, O2.

    So I am immediately troubled by 'small N2' in the first.

    I think we have been through all this before here, and concluded that the pure N2 filling was a good thing because it excludes water. That one changes volume a lot with temperature, which is why people don't like it (or free-range air) in their tires. the ldeal gas law PV=nRT does not apply well to H20, when the important temperature range includes that where water condenses

    The bigness of CF3I will certainly limit its rate of effusion. But heck guys, Xenon is surprisingly cheap. CO2 even cheaper. But breathe Xenon and your voice will sound like Don LaFontaine (RIP)

    Infrared absorption of CF3I is 40% of CO2. Derived from the other fluorocarbons already floating about, chemists have not trouble finding trifluoroacetic acid in rain water already. I would rather oppose this.

    Wanted to say that trifluoroacetic acid was how The Blob was killed, but no it was trichloroacetic acid. Both are chemicals that you ought to avoid.

    Seems obvious to me why nobody sells CO2 for tire fill. Won't make any dang money at it.
     
  10. frodoz737

    frodoz737 Top Wrench

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  11. wjtracy

    wjtracy Senior Member

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    My understanding is CO2 leaks pretty fast. If I understand, the permeation (leakage) rate will be a function of both molecular size and solubility of the gas in the membrane. CO2 apparently (although a little bigger kinetic diameter than N2) leaks faster due to solubility/affinity for the rubber.

    I agree the CF3I does not sound too good for the environment, but I must presume its is a commercial product is why they can devote a small portion of the production to STAYFILL.
     
    #11 wjtracy, May 28, 2015
    Last edited: May 28, 2015
  12. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    I have 2 motorcycles.
    Since each one only has two tires, and I sorta need them both to be PROPERLY inflated, there is absolutely no benefit in this product for me since only a moron would ride a motorcycle wihout checking tire pressures regularly - no matter what gas in inside the tire.
     
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    Seems to me the more esoteric your tire air, the more you paint yourself into a corner: no more airing up with a DIY pump or at a common gas station. It's "gluten free" for cars. :rolleyes:
     
  14. wjtracy

    wjtracy Senior Member

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    OK then bicycles is the main use
     
  15. bisco

    bisco cookie crumbler

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    that's it! there's no end of morons on bicycles.;)
     
  16. RRxing

    RRxing Senior Member

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    Can anyone point us to definitive studies (plural!) that conclusively determined the advantages of pure N2 to good old breathable air for tires? I still smell snake oil, but I can be persuaded otherwise if presented with facts...
     
  17. wjtracy

    wjtracy Senior Member

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    Consumer Reports did tests on N2 around 2008. It's proven but not huge deal.
    Typical tire might go down say 5-psia with Air over 12 months, with N2 down 3 psi: about 33% less leak rate. So CR said just check your tires pressure and skip the N2 (which is perhaps a little too dismissive),

    In addition to Consumer Reports, many tire manufacturers have public written statement saying they like N2 since it holds pressure better. I could post these but this thread is not about N2.

    The STAYFILL chart above says it all. The leak rate depends on the nature of the gas in the tire. Also you know Helium leaks faster out if a balloon.

    The thing about N2 benefits, it is misundertsood. Some N2 proponents are bad chemists and assign qualities to N2 that violate the laws of the universe. The biggest "bad science" is the oft quoted wrong statement that N2 does not change pressure as much in cold weather. But that's wrong as all gases do that to the same extent even STAYFILL. If you look at the STAYFILL write up, they try to stress yes in cold weather pressure still goes down.

    I did not see any bad science in the STAYFILL web site so that's some background.
     
    #17 wjtracy, May 30, 2015
    Last edited: May 30, 2015
  18. wjtracy

    wjtracy Senior Member

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    I now see the STAYFILL web site does specifically mention use for motorcycle tires...but its very expensive so I understand if you don't want to.
     
  19. Trollbait

    Trollbait It's a D&D thing

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    The advantages aren't worth paying extra for, but take it if a station offers it free.
     
  20. wjtracy

    wjtracy Senior Member

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    Good summary.
    Consumer Reports compared Air vs. N2 ....too bad CR did not fill one tire with O2 to show how fast O2 leaks. But air is 80% N2 so you get most of the benefit of N2 just using Air.