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P85D 19" tire pressure recommendation is now 50psi

Discussion in 'Model S: Driving Dynamics' started by commasign, Apr 6, 2015.

  1. commasign

    commasign Active Member

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    Just had my tires rotated. Tesla is now recommending and inflating tires to 50psi for 19" tires on P85D despite the sticker saying 45psi. Makes sense and may give a bit more range.
     
  2. yobigd20

    yobigd20 Well-Known Member

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    would this be specific to the P85D or 19" on all models? I don't see why a 'D' would be different than the other models.
     
  3. dirkhh

    dirkhh Middle-aged Member

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    I guess a 'D' is heavier with the second motor... (and a P85D is heavier than the 85D because of the bigger rear motor).
    I gotta look what my tires are at; I bought the pump from them when I got my 60 and had a leaking tire early on.
     
  4. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    Was there a service bulletin? Or just a tech who told you this?
     
  5. artsci

    artsci Sponsor

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    That's a very important question as 50 psi is the upper pressure limit for a number of tires. Inquiring minds want to know:)
     
  6. yobigd20

    yobigd20 Well-Known Member

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    Isn't the rear P85D motor and rear P85 motor exactly the same?
     
  7. dirkhh

    dirkhh Middle-aged Member

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    I believe so, but last time I checked the P85 didn't have a motor in front. Hence my comment that the P85D was heavier.
    Having said that, the more I think about this the less I can believe that this alone is justification to raise the tire pressure by 11%
     
  8. sorka

    sorka Active Member

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    My new P85D says 50 psi on the door sticker.

    Isn't 51 psi the max inflation pressure for the Primacys? Mine came 51 psi on all 4 corners from the factory last week. Warm, they're 54 psi.

    I wonder why they changed it? Seems dangerous.
     
  9. bluetinc

    bluetinc Member

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    The psi listed on the sidewall of the tire notes that it is for the tire cold. It is expected to rise above the cold pressure setting when the tire is used.


     
  10. commasign

    commasign Active Member

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    FullSizeRender 11.jpg

    From my service rep. I saw the work order, and mentioned that my door jam sticker says 45psi. He double checked with two techs and the foreman, and they all confirmed that P85D 19" is supposed to be 50psi. From the other posts above, looks like recent deliveries have an updated door jam sticker showing 50psi.
     
  11. yobigd20

    yobigd20 Well-Known Member

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    But the front motor probably only adds 50-75lbs or so....not enough to justify raising tire pressure so high. I mean honestly adding a passenger to the car adds more weight than the front motor does.
     
  12. jerry33

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

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    Reading the fine print on the tire, most are 51. However, that's cold pressure first thing in the morning before driving. It's just fine to have them increase over that during the day. It won't hurt them a bit as tires are designed to be able to do that. Typically there is around an 8% pressure increase after driving on the highway for a bit. This might be 15% if the day gets significantly warmer.

    - - - Updated - - -

    If you look at the load/inflation tables you'll see that the carrying capacity stops somewhere around 45 psi (from memory). The additional pressure is to keep the tire cool at high speeds without adding any load capacity. I really don't understand why people are so afraid of pressure in a tire--as long as they're not putting in way more than what it says on the sidewall. The vehicle placard pressure is a starting point only, not a maximum because it's based on a set of assumptions--change any of the assumptions and the pressure needs to be changed (although with 51 psi tires, there's not a lot of room left if the placard pressure is 50). I suspect the next generation of tires will have even higher pressures.
     
  13. jepicken

    jepicken VIN: 80322

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    My S85, delivered March 28, came with the tires inflated to 50 psi, though the door jam sticker says 45 psi. So the increased pressure is not only for the P85D.
     
  14. yobigd20

    yobigd20 Well-Known Member

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    Googling a bit came up with a few interesting hits. Particularly this older thread where these guys run 60-70psi in 44max psi rated tires to get better mpg. Tire pressure above 44 psi? - CleanMPG Forums There was a mention of someone running 120psi and a mention from an engineer that said tires wouldn't spontaneously blow up until well after 200psi. I may go out and pump up my tires to 50psi and see if it makes any difference. It's probably negligible.
     
  15. Todd Burch

    Todd Burch Electron Pilot

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    Since the Ds are not traction limited, it makes sense to raise the pressure for reduced tire wear and better efficiency. The RWD models (Ps at least) are traction-limited typically, so that ends itself to lower pressures to increase the contact patch.
     
  16. yobigd20

    yobigd20 Well-Known Member

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    My P is not traction limited bc I'm running 255/45ZR19 Michelin Pilot Sport A/S 3 but this tire has def taken a 10-20% hit to my Wh/mi. Running higher psi to get some of that back would be nice if possible.
     
  17. Bet TSLA

    Bet TSLA Member

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    I got my P85 19" Michelin tires rotated on March 23. They inflated to 45psi according to the work order. Just another data point.
     
  18. jerry33

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

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    That would be on new tires with no injuries. For long term, I wouldn't go anywhere near that. Anecdote: A 4x4 buddy put 150 psi in the spare so that he could use it to rapidly inflate his other tires as trail conditions changed without carrying a lot of extra weight. Worked for about six months, then the cords unwrapped from the bead.

    I think you may be surprised. I can always tell when my tires are down a couple of psi.

    - - - Updated - - -

    That's my take on it. I've been running 51 for a couple of years now, as i consider the vehicle placard pressure to be a pressure I never want to go below (in the Model S and other on-road cars, SUVs 4x4s, etc. are another story).
     
  19. mknox

    mknox Well-Known Member

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    FWIW, a couple of times my service center has reported that my tire pressure was too low (no dash warning light) and had adjusted. When I checked cold myself the next day, they are usually set to around 50 PSI. This is on my 2 year old S85. I had always set to 45 when checking myself.
     

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