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Could 4 pound increase in tire pressure be cause of new vibration sound in cabin?

Discussion in 'Model S: Driving Dynamics' started by Andyw2100, Apr 11, 2015.

  1. Andyw2100

    Andyw2100 Well-Known Member

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    On Friday morning I increased the pressure in my P85D's 19 inch Pirelli Sottozero Series II snow tires (which are coming off in two weeks) from 46 PSI to 50 PSI, as per the new Tesla recommendations. On Friday afternoon I drove the car for the first time after increasing the tire pressure, and heard a vibration / rattle sound that I had not heard before that sounded like it was coming from somewhere around the dashboard, on the passenger side, after the car went over any small rough spot or seam in the road. I've driven the car a few more times today, and the vibration / rattle sound has persisted. Tomorrow, if I can get my wife to cooperate, I am hoping to get her to drive while I sit in the passenger seat and try to isolate where the sound is coming from.

    If anyone has experienced this, and can point me in the right direction, I'd certainly appreciate it.

    But I'm mainly interested in knowing if people think this new vibration / rattle sound could have manifested itself because of the four pound increase in tire pressure. If not, it's awfully coincidental.

    Thanks.
     
  2. jerry33

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

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    Whenever you change something, it's possible that there will be side-effects--something loose is now noticeable. Use the pencil test as a first attempt to isolate the problem.
     
  3. Barry

    Barry Member

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    Pencil test? Please explain, Jerry.
     
  4. jerry33

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

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    1. Get a pad of paper and a pencil (a felt pen works too, but not a ball point).

    2. Have someone drive the car until it exhibits the symptoms then keep that speed steady.

    3. Tap the pencil on the pad in time to the noise/vibration for one minute. (It can be done shorter time increments, but then you have to do more math.)

    4. Count the number of dots.

    This gives you the RPMinute for the vibration, and will often eliminate items that couldn't possibly be it. For example Tesla tires have an RPMile of around 550, so if your speed was 30 mph and there were 400 dots, you can rule out the tires because the tires would give you 275 dots.
     
  5. Andyw2100

    Andyw2100 Well-Known Member

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    Thanks for the advice, Jerry.

    The pencil test as described below wouldn't work because the vibration, when it occurs, only lasts for a second or two immediately after having passed over a small bump or seam in the road. On really perfectly smooth road, I can't hear it. But if there is any irregularity to the road surface, I'l hear it, but just very briefly each time the car rolls over an irregularity.

    Does that make sense?
     
  6. jerry33

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

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    That sounds like there is something rattling around, perhaps in the glove box or even the cup holders. This kind of rattle tends to be either very obvious (sunglasses), or incredibly difficult to find.
     
  7. 4us2bev

    4us2bev Member

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    FWIW, I had a persistent vibration after my Reus stereo upgrade. Turns out it was the shell of my USB stick vibrating against the body of the stick. You could also try emptying your console area and glovebox.

    -- David
     
  8. mspohr

    mspohr Active Member

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    If you want to go hi tech, there is a app for Android (and probably similar for iPhone) called Seismograph which gives nice 3D graphs of vibration. Just set your phone on a solid surface and it will measure the vibration and you can see (and save) amplitude and frequency.
     
  9. Andyw2100

    Andyw2100 Well-Known Member

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    Thanks.

    I had checked my glovebox first. I knew the only thing in there that could rattle was a small flashlight. (I bought one that uses one of the same 7104 batteries the car does.) That wasn't it. And there is nothing and never has been anything in the cupholders. (I had checked anyway, in case my wife had put something there without my knowing it. She had not.) I also had checked the door pocket areas, as we once had a "discussion" about her keeping a parking pass there. (She was pro--I was con. I didn't like the potential for rattle, and the idea that it could fall out and be lost.)


    Winner, winner, chicken dinner! (Well, maybe.) At least I hope that's it.

    While we were out driving around, we actually identified this on our own. I was coming back here to post, and post a picture, and found these ideas. While we are not 100% sure this is the cause of the rattle, I'd say at this point we're 90% certain. We just haven't driven enough with the USB memory stick removed to be certain.

    Here is a picture of my memory stick and the adapter:

    USB Memory.jpg

    That outer shell slides forward and back, and can lock in the forward position to protect the end of the USB adapter when not in use, if you were, say, carrying the USB stick in your pocket. But when inserted, the shell--the darker area--slides loosely back and forth, or, in my case, up and down because I have the adapter in place to change the orientation of the USB port so that the memory stick is flush against the car and not sticking out. (I bought that from Abstract Ocean, before I had the car.)

    Since I really don't need to protect the end of the USB stick when it's not in use, but I do need it to not rattle, my plan is to apply a couple of drops of crazy glue and attempt to glue the shell into the open position permanently. (Anyone think that's a terrible idea for some reason, or have a better idea?)

    I really appreciate the help! Just more evidence of how awesome TMC and the people that use it are!
     
  10. Terra117

    Terra117 Member

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    Absolutely it could.

    Racing teams work in units of 10th of pounds of tire pressure.

    Most vehicles I have owned recommend 35psi.

    Tesla is recommending 50psi which is near the max for common tires, including those I have run at 35psi.

    I once complained about ride qualities/noise on my M3. The dealer's response was it was a result of running at 40psi. They lowered the pressure to 35psi and all issues disappeared.

    My belief is that increase in tire pressures don't have a linear effect, but exponential. The differences being most pronounced at high pressures, especially when approaching max pressure for a tire.

    I question Tesla's reasoning/motivation for increacing tire pressure. My impression is that it is to protect fragile wheels on horrendeous road surfaces, and ignores ride quality and noise issues of the recommendaton.

    That said, if you are attempting VMAx (at Bonneville for instance), ramp the tire pressures up to max for those runs. Max speed runs are vastly differnt from everyday driving conditions, especially where comfort is a primary concern.
     
  11. Andyw2100

    Andyw2100 Well-Known Member

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    Yes, I'm reasonably confident that, assuming it was the USB stick shell rattling, it was the increase in pressure that caused it. Because I've been using that USB stick for a while, and I would have noticed the sound before. I noticed the new sound within five or ten minutes of getting in the car after increasing the tire pressures.
     
  12. xy46

    xy46 Member

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    Curious as to how people are being informed of the new tire pressure recommendations and Tesla's stated reason for doing so?

    I had my car in to the service center on 3/31 to have the Next Gen seats installed, and since then have noted that I thought the car was taking road bumps rather harshly - just not as smooth riding as I remembered. I kept telling myself that I needed to check the tire pressures assuming that maybe they were a little high now that the weather has warmed up. Then I read this forum, and looked on my service center report and see that the tire pressures were increased to 50 by the service center. I am planning to take them back down to 46 unless there is a strong reason not to do so.
     
  13. Andyw2100

    Andyw2100 Well-Known Member

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    There is talk in other threads of uneven tire wear. I think the general consensus is Tesla is changing the recommended pressure to minimize this tire wear. So the strong reason to leave your tire pressures set to 50 would be to minimize wear.
     
  14. Tdriver

    Tdriver Member

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    I think any uneven tire wear at these high pressures would be due to camber changes. Most cars will have pretty even wear at anything above 32 psi if alignment is ok. I will bet the high pressures for Tesla are to help maintain minimum rolling resistance and maximum range with little regard to comfort.
     
  15. Andyw2100

    Andyw2100 Well-Known Member

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    Well, that's not what's being said in the other threads. I'm just repeating and referencing what I've read (bold added):

    P85D 19 tire pressure recommendation is now 50psi - Page 3

     

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