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Some insight on TPM from my Service Advisor

Discussion in 'Model S' started by boonedocks, Sep 3, 2015.

  1. boonedocks

    boonedocks Member

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    On a recent visit to have a screw replaced in the cup holder slider and my noisy brake pedal looked at and finally LTE upgrade (well worth it by the way) I asked my SA not to allow any one to mess with my FOBO tire sensors as my pressure was perfect as I showed him on my phone. He said "wow that's cool, why did you install those tho?" I proceeded to tell him that I have 21" wheels and don't want to find out the hard way that one was too low. He said the car will warn you!! I said yes but at what point? You can't monitor the pressure without physically cracking so I invested in the FOBO sensors. I said if my car told me the same pressure I wouldn't need them.

    Finally the reason for NOT displaying the tire pressure came out. There is such a fluctuation in pressure that people freak out thinking there is something wrong when really everything is fine.

    I can personally attest to that now. I have had the FOBO sensors for about a month and set all tires at 42psi in my garage at 81 degrees on a Sunday morning. There is as much as a 11 degree difference from 39 to almost 50 depending on driving, ambient temperature and road temperature.

    Here is a screen shot of what the systems looks like on the iPhone app:
    image.png
     
  2. AmpedRealtor

    AmpedRealtor Active Member

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    I think the SvC gave you a silly reason. Every other car on the planet at half the price shows tire pressure readouts.

    At least he/she didn't say the car wasn't capable of it. That's a relief. My service center also told me that they can see individual tire pressures in their backend systems on my August 2013 car.
     
  3. ERP

    ERP Ludicrous Member

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    Car manufacturers have been during this for years with the engine coolant temp gauge. They set a large temp range to register perfectly centered on the gauge. This is why newer cars appear to warm up more quickly than older ones. The temp gets to 150 F and the needle moves to center. This unfortunately turns it into a 'dumb' gauge and makes trouble shooting more difficult.

    I have the FOBO sensors for my Elise and use them on track days. I'll see an 8 psi increase in ~10 minutes of track time. PV=nRT
     
  4. boonedocks

    boonedocks Member

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    I don't see it as "silly" at all. If an uninformed driver saw their 42psi tires at 39 or 50 they very well might freak out. I understand exactly were he was coming from.
     
  5. kenkamm

    kenkamm Member

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    This.
     
  6. AmpedRealtor

    AmpedRealtor Active Member

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    Huh, then I wonder why all of the other car manufacturers are giving their drivers information over which they might "freak out"? Is Toyota unnecessarily "freaking out" its customer base by offering the convenience of individual tire pressure readouts? Or is the SvC advisor saying that the intelligence of the average Tesla customer is too low to give them information that every other car maker feels their customers are intelligent enough to process?
     
  7. skboston

    skboston Member

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    I've seen the tire pressure readings on the screen while it's in "Maintenance" mode, I really don't know why they don't just make it visible to all owners...
     
  8. islandbayy

    islandbayy Active Member

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    I can attest. I keep mine all at 50psi. Much better ride in my opinion, and better range too. the recommended pressures feel too squirly to me.

    Anyways, since the radiator vents, well, vent directly on the front tires, on a hot day with the AC going, or supercharging during the summer time, I've measured the front tires MUCH hotter, and as much as 10 psi higher then the rears. It also will trip the over-pressure alert on the car.

    So solution to that, I keep the fronts 1-3 PSI lower then the rears, Problem solved. I suppose, straight Nitrogen Fill would solve that, but my tires just leak too darn much. I add about 5lbs/week to all 4. Been like that since factory :(
     
  9. eye.surgeon

    eye.surgeon Member

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    I had real time TPM on a motorcycle and I agree, it's shocking how much the pressure fluctuates from early on a cold morning to the hot end of that same day.
     
  10. jerry33

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

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    But knowing how much it increases normally lets you also know when there is a change that warrants investigation.
     
  11. Tdriver

    Tdriver Member

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    I got a tire pressure warning yesterday. The display said my RR was low. I checked and it was 1-2 lbs lower than the other three.
    The car knows whats going on.
     
  12. apacheguy

    apacheguy Sig 255, VIN 320

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    Apparently only the newer VINs have this capability. The others merely alert that TP is low but do not specify the tire.

    BTW, when I first saw the subject I thought TPM = Trusted Platform Management in light of the Defcon hack
     
  13. PatD

    PatD Member

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    My 2006 Acura TL showed me the pressure. Of course it fluctuates! Every 10 degrees change in air/tire temp results in 1 PSI change. So imagine in winter when you jump in the car in the morning and it's 20 degrees ambient. What happens to that tire pressure when you arrive at work 30 minutes later and the tires are 80 degrees?
     
  14. Only Trons

    Only Trons Member

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    Wow!!! 5 lbs per week? I've experienced pressure loss like that only when my tires/wheels/stems had a problem.
     
  15. Soolim

    Soolim Member

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    I agree 101%. In any case, seasonal temperature changes should be accounted for by the owner in adjusting tire pressure (when cold). Just give us the reading for our convenience and we will take care of correcting tire pressure as needed.

    - - - Updated - - -

    It is silly because tire pressure changes due to ambient temperature will be uniform for all 4 wheels, and the driver would understand that.
     
  16. boonedocks

    boonedocks Member

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    That's why I purchased a FOBO set. Silly or not, you few (myself inccluded) would be fine with the car display, but the masses freak out when they see a 42psi tire at 38 or 50 when I it is completely normal on a daily commute. Life as is has to be dumbed down for the masses. That is the real "silly" part
     
  17. hpham007

    hpham007 Banned

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    No they don't. Quit making up stuff to support your silly reasoning.
     
  18. bollar

    bollar Disgruntled Member

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    IMO, 38 is not normal and it should be corrected -- especially on 21's. The cold tire pressure really needs to be at least 42 and one of the owner's tasks as we get into fall and winter is making sure the tires remain inflated to the correct pressure as ambient temperatures drop.

    Otherwise, every car we have owned over the past fifteen years has had TPMS displays and I don't see any "Chicken Little" behavior from my better half. She happily lets her tires get -20 PSI without a care in the world. :cursing: :smile:
     
  19. boonedocks

    boonedocks Member

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    The reality is "It is what it is". Not making that up. It's not my "reasoning"
     
  20. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    I suspect the TPMS system changeover that occurred last year is probably a lead-up to Tesla delivering some of those values to us. Not sure we'll ever see it in the classic cars with the older TPMS system, but at least in the newer ones it reports which wheel is low, meaning the alert system knows more information. I wouldn't be surprised if it appeared down the road somewhere.
     

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