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Tire pressure

Discussion in 'Model S: Driving Dynamics' started by mackgoo, Feb 3, 2015.

  1. mackgoo

    mackgoo Member

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    What's everyone running for tire pressure? The reason I ask is I've been maintaining pressure at 45 psi. I recently had my tires rotated, when I did my weekly pressure check I found my cold pressure to be 47. Obviously the service center brought the pressures up to 47 psi. I "corrected" to 45. Now I'm thinking I liked the way the car felt at 47 and if that's what the service center left it at, maybe that's the way to go. I guess I should speak to the service center also.
     
  2. benjiejr

    benjiejr Technogeekextraordinaire

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    45 here
     
  3. roblab

    roblab Active Member

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    I was running my tires at 50. Service put them at 46. Then last time, Service put them at 45. I don't notice any difference. Temperature swings change the pressure a tiny bit, too, so it's variable. Starting at 45, driving fast on a sunny day, they could go up to 47. I wouldn't base too much driving feel on what I think my pressure is at any given moment, because it probably isn't/
     
  4. David99

    David99 Active Member

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    #4 David99, Feb 3, 2015
    Last edited: Feb 3, 2015
    According to test you can get a 6% increase in range if you inflate the tires by 5 psi over recommended. So that's what I'm doing. I'm still far away from the 55 maximum for the tires.

    Here are the results from the Mythbuster test
    Control, 35psi (manufacturer recomendation)

    tyres at 10psi = 3.7% increase in consumption
    tyres at 30psi = 1.2% increase in consumption
    tyres at 40psi = 6.2% decrease in consumption
    tyres at 60psi = 7.6% decrease in consumption

    Test car Ford Taurus
     
  5. scottm

    scottm Active Member

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    45 psi.

    +/- 1 psi (gauge error)

    But I haven't checked for months.

    I rely on TPMS's to tell me if one, or all, are too far out of whack.

    Damn! Now, I'm going to worry about it and check them tonight.

    Thank you.
     
  6. jerry33

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

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    1. Always check the tire pressure the morning after any work is done on the car.

    2. Use an accurate gauge (regardless of what you might hear or read, there is no cheap accurate gauge).

    3. If the ambient temperature was different today than yesterday, the tire pressure will change.

    4. The vehicle placard pressure is based on a set of assumptions--change those assumptions and the pressure needs to change. Most people do things backwards. They use the speed limit as the minimum speed, and the vehicle placard pressure as the maximum pressure. In most cases the vehicle placard pressure is the pressure you never want to go below for normal on-road use (doesn't include track use or off-road use although I don't suppose many owners do off-roading in their Model S).

    5. By the time the TPMS warns you there is probably already underinflation damage done to the tire. Only rely on your own accurate pressure gauge.
     
  7. mackgoo

    mackgoo Member

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    So, based on your accurate pressure gauge. What pressure do you maintain in your S?
     
  8. jerry33

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

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    I use 51. In Texas the typical problem is heat. The cooler you can keep your tires the longer they will last (and the safer you will be). As you drive, the tires will increase pressure until the cooling effect of air equals the heating effect of flexing (which is reduced as pressure increases) and ambient temperature increase over the day (this is called reaching thermal equilibrium), so you can either wait for the tires to heat up enough to even out or you can put some air in to start with. The end pressure will be about the same, but the tires' temperature will be far different between the two approaches.
     
  9. mackgoo

    mackgoo Member

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    If you over inflate can't you run the risk of the tires running too cold?
     
  10. jerry33

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

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    1. Overinflation is setting the pressure to higher than the maximum rating shown on the tire's sidewall when the tires are cold (first thing in the morning before driving). Adjusting the pressure to suit your driving conditions is NOT overinflation.

    2. If the ambient temperature is below what the tires are designed for, inflation doesn't make a bit of difference (e.g. some high performance summer tires' tread compounds can be ruined if used at below 40 F / 5 C). It only takes a mile or two of driving to warm the tires up.

    3. Other than the hp tires at low temperatures mentioned above, there is virtually no such thing as too cold for ordinary road use (track use is another story). Certainly not when the temperature is 25 C or more.
     

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