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Inaccurate Tire Pressure Readings

Discussion in 'Model S' started by PetersRD, Nov 7, 2018.

  1. PetersRD

    PetersRD Member

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    Jul 22, 2018
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    Location:
    Scottsdale, AZ
    My 2018 Model S came up with a low tire pressure warning yesterday, showing three tires at 40 psi and one at 38. I checked all four and found that the three reporting at 40 were actually at 44, and the one reporting 38 was at 43. I used two different tire gauges when I measured. So is there a way to calibrate the car's TPMS so I can believe the readings?
     
  2. Dan Baldwin

    Dan Baldwin Member

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    Location:
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    I went through this same thing. Finally got ahold of service who said to reset the TPMS (forget where in settings this is), despite the fact that the manual warns not to do it. Before I did it I made sure that the tires were cold and were within 0.5 psi of the required values. I haven't had any trouble since.
     
  3. PetersRD

    PetersRD Member

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    Thanks, I'll try that in the morning after inflating to 45 while they're cold. Last night I did do the TPMS reset (ignoring the warning) but it made matters worse, lowering two of the other tire pressures to below 40. But they weren't cold and I had not added any air. Now it says I have three low tires. Mind you they're really still at 43+
     
  4. GHammer

    GHammer What a long strange trip its been.

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    What kind of tire gauges are you using? The pop-up turkey thermometer type that are so prevalent are notoriously inaccurate. If it's those type I would trust the TPMS over the gauges. I use a large analog dial gauge and it is always been spot on with the TPMS on a range of cars.
     
  5. PetersRD

    PetersRD Member

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    I used two of the stick type, one of which (plastic) read waaaay high, so I tossed it. The other is metal and is my old reliable, but I'm tossing it, too in favor of getting a new one. After reading a bunch of reviews of types and brands, I just ordered a digital gauge from Amazon. I also have a gauge on my compressor, but I'm not sure how accurate it is. Should have the new one on Friday, so Saturday morning I'll give it a shot.
     
  6. steelers100d

    steelers100d Member

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    What is the proper setting for the tires? On a model S (18)?
     
  7. GHammer

    GHammer What a long strange trip its been.

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    It's listed on the car's doorjamb, however in general it is 45psi for 19's and 42psi for 21's.
     
  8. PetersRD

    PetersRD Member

    Joined:
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    Location:
    Scottsdale, AZ
    So my $3.95 digital gauge came in and I tried it on the Model S. It reads within 1/2 psi of what the car reports, so my old stick gauge was reading high by about 3 psi. After airing up the tires to 41 and driving for an hour or so the low-tire alert went away. My wife already thinks the ride is too bumpy with the tires at 41, but I'm going to put them at 45 and see what she thinks.
     
  9. Dbj77

    Dbj77 Member

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    Location:
    Washington, DC
    Which type of gauge did you buy from amazon? I’m having the same problem- would like a more accurate reading. Thanks!
     
  10. How D

    How D New Member

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    Oct 17, 2019
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    Location:
    Colorado Springs, CO
    My tires have been consistently reading low by 2-3 PSI at all times on all tires. I spoke with ranger today and he said the low readings are common. I verified my pressures with a digital tire gauge from Amazon as well as my own pump, which both agree at 45 PSI. When I inflate to 45 PSI the Tesla tire senor reads about 42 PSI. I have not tried to reset, as the difference of 2-3 PSI is consistent over time.
    I stronly recommend testing pressure each month as PV = nRT and the pressure is strongly dependent on temperature. I tend to fill to 45 PSI when temperatures are the lower side that month. Also, as a chemist, I believe using N2 is a waste of money unless one lives in a very humid climate.
     
  11. Barry

    Barry Active Member

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    It is NORMAL to read 3 psi low along the front range. There's an explanation somewhere on the tirerack.com web site, but in a nutshell, since the pressure sensors have no external reference, they read 3 psi low at 5000-6000 ft ASL. If you travel to sea level and recalibrate them (which is currently impossible as they removed the recalibrate button in a recent firmware update), it would be correct. Just add 3 to what it reads.
     
  12. jdw

    jdw Supporting Member

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    Location:
    Montreal, Canada
    Have the same problem and am at 170 feet above sea level. While I can easily add 3 to the number, it is a problem if I actually want to run at 42PSI actual, as 39 PSI sets off the low pressure alert. Used to be able to reset the TPMS and fix things like this, but that option is now gone. I'll live with it until I have a reason to visit service. The outside temperature also reads 3-4 degrees high ...
     
  13. Big Toys

    Big Toys Member

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    Jan 19, 2019
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    Location:
    Florida
    One of the brand name auto store used to sell a round analogue gauge with a dial indicator. I've had it for years, it's still accurate, and no batteries to replace.
     
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