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Differential tire pressures

Discussion in '360/430' started by porcupine, Aug 28, 2012.

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  1. porcupine

    porcupine Rookie

    Jul 23, 2010
    38
    #1 porcupine, Aug 28, 2012
    Yesterday during the track day I did an experiment. After each session I measured the tire temperatures and pressures. I run Bridgestone Potenza 050A. Cold tire pressure (in the garage the night before) were set at 32 front and 35 psi rear.

    The track I was on has twice as many left turns then right and as a result I noticed higher temperatures and pressures on the right front and rear tires compared to left. The right/left pressure difference was about 2psi.

    If I started with cold pressure differential of 2 psi between the right and left hand side of the car then most probably the final hot pressures will be equal.

    My question is; how would this change the handling of the car (if at all). Has anyone tried something like this?
     
  2. Noblesse Oblige

    Noblesse Oblige F1 Veteran

    Nov 7, 2011
    6,114
    Three Places
    #2 Noblesse Oblige, Aug 28, 2012
    A non expert guess. Based on the idea that the front tire with the higher pressure will stick a bit better, you would tend to have less understeer in left turns and more understeer in right turns. The rear would stick a bit better and move less. Whether any of us would notice a difference is another question.
     
  3. DanS*

    DanS* Karting

    May 29, 2012
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    Manhattan Beach, CA
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    #3 DanS*, Aug 29, 2012
    I think the correct way to do this is to take three temp measurements on each tire.
    Inside, center and outside. You want to adjust the pressure so that the center is the average of in and out. If you're on a banked track, or a track like yours, you'll wind up with uneven cold pressures.
     
  4. Trent

    Trent Formula 3

    Dec 10, 2003
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    Indialantic, FL
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    Trent
    #4 Trent, Aug 29, 2012
    +1; Tire pressure is used for a few things, assuming we isolate tire pressure as a means to cool said tire, then the absolute HOT tire pressures are not your goal, your goal should be to have even tire temperatures right after you exit the track. Yes take the outside, center and inside of left and right side front and rear. Then change the pressure to make sure all tires are at their optimum recommended compound temperature for the current track conditions.

    *This is what we did in motorcycle road racing, albeit with only front and rear, not left and right, but its really the same if you think about it. The compound works best at a specific HOT temp. Too hot and it wears fast, or gets greasy, too cold and its not sticky enough.
     
  5. porcupine

    porcupine Rookie

    Jul 23, 2010
    38
    #5 porcupine, Aug 30, 2012
    Thanks everyone. I actually did take tire temperatures on inside/middle/outside but did not mention this in my original post. The differences between these three temperatures on each tire were plus minus 1.5 degrees F. But there were differences between right hand side tires and left hand side tires which are of course directly correlated with tire pressures that I mentioned.

    If I understand your responses correctly; I should aim for similar temperatures on ALL tires with the constraint that across the three points on each tire the temperatures should also be even and the overall temperature should match the compound’s proper hot temperature.

    Thanks again.
     
  6. DanS*

    DanS* Karting

    May 29, 2012
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    #6 DanS*, Aug 30, 2012
    Yes. So on track you'll have the correct temp all around. Cold you'll have different pressures left and right (and usually front to back).
    With 4 different cold pressures, notes will be extra handy.
     
  7. Trent

    Trent Formula 3

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    #7 Trent, Aug 30, 2012
    +1; Agree and agree.
     
  8. porcupine

    porcupine Rookie

    Jul 23, 2010
    38
    #8 porcupine, Aug 30, 2012
    Perfect. Thank you all for helping.
     
  9. justinn

    justinn Karting

    Jan 5, 2011
    114
    Austin TX
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    #9 justinn, Aug 30, 2012
    Out of curiosity...

    How long did you wait before measuring the temps? 1.5F difference on the tire only? I think they had already cooled quite a bit.

    The pressure variation between hot and cold is normal. Set your tires by the temperature. It is not uncommon to use varying tire pressures depending on how your track is set up.

    Justin

     
  10. porcupine

    porcupine Rookie

    Jul 23, 2010
    38
    #10 porcupine, Aug 31, 2012
    Tire temperature mesurements were not as scientific as i wanted it to be. First off all it was after a cooldown lap and due to other reasons i was not able to measure tempretures immidiately after i came to a stop. But in general i took measurements a few minutes after i stopped.
     
  11. DanS*

    DanS* Karting

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    #11 DanS*, Aug 31, 2012
    There's usually the issue of a cool down and delay.
    You could always pull into the pits just before the end of the session.
    Anyway, as soon as possible i.e., less than 3 minutes is probably fine for amateurs.
    Tire pyrometers are a lot more accurate that non contact IR Thermometers. Also a lot more expensive.
     
  12. ferrari355gtb

    ferrari355gtb Formula 3

    Nov 3, 2003
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    #12 ferrari355gtb, Sep 1, 2012
    Using nitrogen in the tyres ?
     
  13. porcupine

    porcupine Rookie

    Jul 23, 2010
    38
    #13 porcupine, Sep 1, 2012
    No nitrogen. Just air. I also used a tire pyrometer with tire temperature measuring probe which is like a little needle that you stick into the tire.
     
  14. DanS*

    DanS* Karting

    May 29, 2012
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    Manhattan Beach, CA
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    #14 DanS*, Sep 1, 2012
    +1
    Nitrogen is 98% hype. Tire pyrometers are much better than IR sensor, But they ain't cheap.
     

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