How much tire pressure for 1/2 mile?

Discussion in 'SRT Hellcat Racing Forum' started by roostinyfz, Dec 4, 2015.

  1. roostinyfz

    roostinyfz Hellcat Member

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    I'm running the 1/2 mile at a 40 mph roll with summer Pirelli tires here in Phoenix next weekend. How much tire pressure should I run? Is 20 lbs to low?
     
    Last edited: Dec 5, 2015
  2. BODUKE

    BODUKE Gold Member

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    I think you need to run max air pressure.
     
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  3. Lord Hellcat

    Lord Hellcat Gold Member Hellcat Car Club Gold Supporting Member HCC UK President HCC Charter Member

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    Standard pressures which are from memory 32psi all around.
     
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  4. roostinyfz

    roostinyfz Hellcat Member

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    People are running 19lbs in the 1/4 mile. Traction is a major problem. Why not lower it down at least some for the half mile. I'm definitely not running max tire pressure at 50 psi that's just crazy.
     
  5. Teo

    Teo Judge Yooper

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  6. roostinyfz

    roostinyfz Hellcat Member

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    Last edited: Dec 5, 2015
  7. Hemi Rocket

    Hemi Rocket Gold Member

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    For the standing 1/4 you need to lower the rear tire pressure to increase traction and increase pressure in the front tires to minimize rolling resistance. As for a flying 1/2 go up on pressure on all four. Get some heat in the tires a roll the throttle on. Flying starts and standing starts take two different approaches.
     
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  8. Aarcuda

    Aarcuda Gold Member

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    in a drag race you lower the pressures to get more sidewall flex so the tire can bite in at the launch for traction.

    In high speed events (1/5 mile, superspeedway, autobahn, etc) you increase the pressure for stability and less deflection.

    dont think of the high speed at the end of a 1/4 mile as being the same as top speed on the autobahn. its completely different
     
  9. roostinyfz

    roostinyfz Hellcat Member

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    I understand what is being said, however, reading through the threads for 1/2 mile drags, even at a roll traction has been a problem and they have said they needed drag radials and or needed lower tire pressure down. That is why I am asking. I understand you want some stability and this can be an issue, but where I am running stock summer tires, with 20's and run flats to boot, I personally don't think that sidewall flex, stability is too much of an issue in a 1/2 mile drag? Maybe I'm just flat out stubborn and crazy for thinking of it that way? However I don't want to be sideways going 155+ either!

    This is my point about a 1/2 mile drag, it is the same as the 1/4 mile just faster. No corners.
     
  10. Aarcuda

    Aarcuda Gold Member

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    no! You spend a heck of a lot more time at high speed than you do trying to get traction off the line.

    Pump those tires UP! Peddle it off the line until you can full throttle it. I wouldnt want to be the guy dointg 140 mph + with underinflated tires. they will explode- remember the firestone tires that were under inflated?
     
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  11. Teo

    Teo Judge Yooper

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    Learning the extremely hard way, is sometimes the only way for some.:oops: Doing the Research (they are more than willing to help) with the MFG's themselves will yield a bucket full of useful info (tire brands, models and AIR pressure recommendations for 1/2 to 1 mile high speed runs) as to being SAFE vs trying to pick-up an extra 1/10 in a time slip. And ALL of them (the MFG's ) have toll free numbers to call! :cool:
     
  12. BODUKE

    BODUKE Gold Member

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    I gave this same advice.
     
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  13. Fast cat

    Fast cat BANNED Hellcat Car Club

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    Think about it! Do you really want to be running 150+ and wounding if your tires are safe to drive on at that speed ? There is a big difference in 1/4 and 1/2
     
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  14. roostinyfz

    roostinyfz Hellcat Member

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    Ok you guys are right! The rolling resistance in a 1/2 mile drag of under inflated tires is greater than the benefit of traction at a good start. I'm not going to crash my car and die, thanks for the kind prediction Teo.That's why I'm here asking the question.

    However I still maintain that a tire pressure albeit perhaps not safe set at 20-25lbs in a 1/2 mile will not generate enough heat to de-tread and blow out like the firestone ford controversy. There are many people toying with all kinds of tire pressures both in the 1/4 and 1/2 that are much much greater speeds than we run. Particularly drag radials at well over 200 mph with very very little air pressure in them.
     
  15. sublime6spd

    sublime6spd Gold Member

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    Myself and at least one other that have posted in this thread have already run a 1/2 mile.
    Do yourself and all folks at the event a favour. At the very least leave your tire pressure at factory recommended level,
    Do NOT LOWER IT!!
    There was a recent video of a hellcat crashing on a airstrip with a woman driver and I've wondered if the tires were Under inflated and that lead to the crash??!!
    My 6spd was doing 140MPH by the end of the run, try that on flat tires and it won't end well.
    As others have said 1/4 and 1/2 mile are COMPLETELY different.
    Be safe, don't learn the hard way
     

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