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Significance of green dots on rear valve caps?

Discussion in 'Model S: Driving Dynamics' started by Musterion, Jun 30, 2013.

  1. Musterion

    Musterion 18h 03m 37s −24° 23′ 12″

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    I noticed my car and several other cars on delivery have green dots on the rear tire valve caps only. Also on mine the rear tires were inflated about 2psi lower than front. Otherwise all tires equivalent (19" wheels). What is the significance of the green dots? Nitrogen inflation? Something else different for rear wheel prep in factory?
     
  2. islandbayy

    islandbayy Active Member

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    Green dots or valve caps generally indicate nitrogen was used to fill tires instead of air. All 4 of my tires were 5lbs low on delivery, I only have air to top off with.
     
  3. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    That's just fine. Nitrogen inflation is mostly a scam unless it's free. POA (plain old air) is mostly nitrogen anyway. There are valid reasons for nitrogen inflation:

    1. High end race car drivers use it because it's guaranteed to be dry and so the pressure increase with heat from operation is very consistent. This helps when you're trying to tune the suspension for that last 1/100th second in lap time.

    2. Low end racers use it because many small tracks don't have electricity (or water) in the pits and nitrogen is as cheap and safe as anything else.

    3. Underground mine vehicles and subways use nitrogen because in an enclosed space the nitrogen doesn't add to combustion should a fire break out. High altitude airplanes use it for the same reason. There is plenty of oxygen in the atmosphere to support combustion, so for vehicles operating above ground there is no safety advantage.

    The best thing about nitrogen inflation is that it does no harm if you don't have to pay for it. Also if you go to a place that charges for nitrogen inflation, you can be certain they also promote other questionable practices.

    What nitrogen inflation doesn't do:

    1. Make the tires run cooler.
    2. Save energy.
    3. Improve tire life.
    4. Reduce sudden deflations.
     
  4. pimp-boy

    pimp-boy Member

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    Motorweek did a study or "test" with tires that were nitrogen filled and filled with regular air.

    1. Did not improve performance in any way. Track time was the same for both.
    2. Supposed to limit expansion of pressure... but the nitrogen tires had a higher PSI after going through the track by maybe 1-2 lbs as opposed to the regular air.
    3. No change in ride quality. (Motorweek just noted it).
    4. Waste of money!

    They said something like 85% of the air is nitrogen and is a waste to even consider. Good to know that using nitrogen air is basically not beneficial in any way that is significant to use.

     
  5. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    This is true if the air is dry (Motorweek likely used air dryers--highly recommended but not common, and of course they do no good unless there is electricity available to run the air compressor).

    Their basic point (#4. Waste of money) is correct for normal automotive use.

    Other scams to watch out for:

    1. Tire sipeing machines.

    2. Tire truing machines.

    Both of these come around about once every ten years or so.
     
  6. 60TTuC

    60TTuC Member

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    #6 60TTuC, Jun 30, 2013
    Last edited by a moderator: Mar 13, 2016
     
  7. Musterion

    Musterion 18h 03m 37s −24° 23′ 12″

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    All, my question was not on the merits of nitrogen inflation, but why Tesla is prepping the rear wheels differently, and taking the effort to mark them as such. (If indeed it is N2 then I agree it doesn't make sense both in general and to do just for rear). Did your Model S come the same way?
     
  8. J in MN

    J in MN S60 P12635

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    #8 J in MN, Jun 30, 2013
    Last edited: Jul 25, 2013
    On mine about half the cap is green and the other half is silver.
    IMG_0836.JPG IMG_0835.JPG
     
  9. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    No idea. Looks like overspray to me.
     
  10. Musterion

    Musterion 18h 03m 37s −24° 23′ 12″

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    Valve cap OEM supplier

    It is definitely green paint on grey plastic caps, because I can scrape off the green. I don't know the meaning of the green paint used only for rear wheels, but for anyone interested I found the OEM supplier of the valve caps. They are TPMS compatible sealing type from Dorman, p/n 609-130. Available for $7.65 for Qty.50 at Amazon, Amazon.com: Dorman 609-130 Plastic Tire Valve Caps - Pack of 50: Automotive

    photo 2.JPG
     
  11. klevins

    klevins Member

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    "They said something like 85% of the air is nitrogen..."

    How does anyone not know even approximately the makeup of the atmosphere of the planet that we live on? 78%. That's what it is. 78% of the atmosphere on this planet is nitrogen. Most people learn this somewhere between 5 and 8 years old. Jesus.


     
  12. brianman

    brianman Burrito Founder

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    Most humans don't have 100% retention of what they learn. Intentional and unintentional prioritization of information is applied as a coping tactic for limited storage capability. Be happy that your retention and/or prioritization is better than others. Feel free to use it to your advantage. But chastising others for their (perceived) disadvantage seems pointless.
     
  13. Discoducky

    Discoducky Active Member

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    Until reading this thread I had no idea there was a fee to fill tires with nitrogen. I'm still chuckling. In other news the universe is 13.7 billion years old. #ThingsThatILearnedInSchoolButForgotWhenIStartedWorkingForALivingThatDoesNotInvolveScience
     
  14. AireV

    AireV New Member

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    Not quite the same but green markings were shown in another thread where the charge port replacement was discussed. See the image of the chargeport behind the body panel in the link below. You can see the green markings on the head of the screws.
    Many commented that the green color was the check mark for the quality control. Would the green color on the valve cap be a similar protocol?

    First Ranger visit in progress. New Charge Port
     
  15. HHHH

    HHHH Member

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    I was in the car business for 7 years, and they would add an addendum to every car for nitrogen for $89. They would nickel and dime the customers, as well as other dealers (dealer trades) whenever a car would get sold.
     
  16. NigelM

    NigelM Recovering Member

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    Mod Note: some posts went to snippiness. Aoplogies to innocents who got caught up in the move. Play nice everyone.
     

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