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Thread: What is "COLD" tire pressure?

  1. #16
    Registered User greenwald's Avatar
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    Cool

    Quote Originally Posted by 40427 View Post
    AARRGH !!

    My head is going to explode !!

    Tire pressure recommendations sound like oil threads to me.

    What the heck are tire pressures supposed to be on an 85 a R80 with new technology tires ??

    I figure it's got to be different than 27 years ago , but how do you figure it out and get it right for the best long wear ???
    And I took a boatload of pot shots for a suggested 4-step oil change procedure?!

    Apparently, a government committee will need to be formed to look into this "cold tire' phenomenum - then lengthy Congressional hearings to get to the bottom of this!

    (Or, ..... you could just wait until tires are no longer hot from use and just check their air pressure.)
    Kevin Greenwald - Touring Tips Editor
    Nationally Certified Law Enforcement Motor Officer (Ret.)
    MSF RiderCoach # 121656 (BRC,SBRC,IS,IME,SMARTrainer,THE REF Staff)
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  2. #17
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by Greenwald View Post

    Apparently, a government committee will need to be formed to look into this "cold tire' phenomenum -
    Not really. By BMW specifications cold tire pressure is xx p.s.i. at 20 degrees celcius or 68 degrees fahrenheit. So if BMW says the cold pressure should be 36, then they mean at 20C. It would be higher at 22C or 25C and lower at 18C.

    I have a Smartire tire pressure monitor that displays actual pressure, internal tire air temperature, and a temperature correction shown as a + or -.

    When the specified amount of pressure and temperature are programmed in even if the tire is warm and the pressure increased the + or - 1 or 2 or 3 etc tells you whether the correct pressure is in the tire for the existing internal temperature.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  3. #18
    Registered User rkoreis's Avatar
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    From the company website:

    SmarTire for Motorcycles

    SmarTire products are no longer available in the motorcycle market and the company has ceased support for this product category.

    Parts may be available at your local dealer, however, we retain no inventory to support service parts.


  4. #19
    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by rkoreis View Post
    From the company website:

    SmarTire for Motorcycles

    SmarTire products are no longer available in the motorcycle market and the company has ceased support for this product category.

    Parts may be available at your local dealer, however, we retain no inventory to support service parts.

    Sure- mandatory on trucks and buses make that market more lucrative.

    But there are at least a half dozen other TPS makers out there. Not as good but better than tire kicking and the alarm function is very valuable. When a tire gets a little low they alarm!
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  5. #20
    Registered User greenwald's Avatar
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    Talking

    Quote Originally Posted by PGlaves View Post
    Not really. By BMW specifications cold tire pressure is xx p.s.i. at 20 degrees celcius or 68 degrees fahrenheit. So if BMW says the cold pressure should be 36, then they mean at 20C. It would be higher at 22C or 25C and lower at 18C.

    I have a Smartire tire pressure monitor that displays actual pressure, internal tire air temperature, and a temperature correction shown as a + or -.

    When the specified amount of pressure and temperature are programmed in even if the tire is warm and the pressure increased the + or - 1 or 2 or 3 etc tells you whether the correct pressure is in the tire for the existing internal temperature.
    You're the first person I'd lobby to be on the Committee!
    Kevin Greenwald - Touring Tips Editor
    Nationally Certified Law Enforcement Motor Officer (Ret.)
    MSF RiderCoach # 121656 (BRC,SBRC,IS,IME,SMARTrainer,THE REF Staff)
    Iron Butt Association Member # 34281

  6. #21
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    Quote Originally Posted by PGlaves View Post
    A given amount of air in a tire will produce a different pressure reading at different temperatures. So a "recommended" pressure has two values: a pressure reading in pounds per square inch (p.s.i.) or in Bar, or some other standard; and, a temperature.

    BMW specifies recommended "cold" pressures at 20 degrees Celsius, which translates to 68 degrees Fahrenheit. BMW actually specifies pressures in Bar (1Bar = 14.56 p.s.i.) such as 2 Bar, or 2.1 Bar, or 2.2 Bar etc. Those specifications in Bar are converted to p.s.i. in U.S. publications.

    BMW specifies pressures to the nearest .1 Bar = 1.46 p.s.i so are actually less fussy that many riders tend to be.

    So the short answer is that to be precise, "cold pressure" ought to be at 68 degrees. When checking add a pound if it is a bit warmer and subtract a pound if it is a bit colder. You will likely wind up within 1/10th Bar.
    Owner's Manual of my '12 GSA says 68 degrees. I run 36F/38R. Don't ask me what kind of oil I use or how often I change it!

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