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Is your Model S suspension feeling less nimble?

Discussion in 'Model S: Driving Dynamics' started by ToddRLockwood, Aug 20, 2014.

  1. ToddRLockwood

    ToddRLockwood Active Member

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    #1 ToddRLockwood, Aug 20, 2014
    Last edited: Sep 2, 2014
    Recently, I thought my suspension was showing premature wear. My Model S felt a little sloppy on anything but smooth new pavement.

    The solution was very simple: I re-torqued the car's lug nuts. Even though I had done this two months ago, all but two of the car's 20 lug nuts were below spec, some taking nearly a quarter-turn. I don't think I was close to losing any of them, but apparently they were just loose enough to allow some wheel play.

    Given the weight of the Model S and the forces generated by its impressive cornering, this should not come as a big surprise. On top of this, the roads in New England are in particularly bad shape this year due to an unusually cold winter. Moral of the story: re-torque your wheels often! Tesla does this as a matter of course whenever a car comes in for service. But if you have a wheel removed for any reason, the lug nuts should be re-torqued after 50 miles of driving. Many tire dealers require you to come back to have this done.

    The easiest solution is to invest in a quality 1/2-inch torque wrench. There are plenty of decent ones on the market, but I'd be inclined to get the same one that the Tesla Rangers use:

    Snap-on Industrial Brand CDI Torque 2503MFRPH 1/2-Inch Drive Adjustable Micrometer Torque Wrench, Torque Range 30 to 250-Foot Pounds - - Amazon.com

    You'll also need a 21mm 1/2-inch-drive socket and a 4 or 6-inch socket extension. If you're not familiar with the procedure, have someone show you. It's not difficult and only takes about five minutes.

    The standard torque setting for either size wheel is: 130 lb/ft or 175 Nm. (Note: This is not listed in the owners manual.) If you have your tires changed at a non-Tesla dealer, be sure to give them this torque spec. Chances are, they've never seen a torque spec this high before. It's also a good idea to request that they "hand-torque" the lug nuts.

    -----------------

    UPDATE

    I would not have believed re-torquing would make such a difference without experiencing it first-hand. I've owned and maintained Ferraris in the past and never noticed this before. (The Ferrari torque spec is 40% lower than the Model S.) The difference, no doubt, is in the vehicle weight and the wheel diameter. These factors account for both the tendency for lug nuts to loosen, and the effect that "loose" lug nuts have on handling.

    I'm running 21-inch wheels with Michelin Pilot Super Sport XL tires on my P85. Both the tendency for lug nuts to loosen and the subsequent effect on handling are probably magnified with the 21-inch wheels due to their diameter and the stiffer sidewall on the 21-inch tires. Even so, I would not hesitate to check 19-inch wheels regularly too.

    The Model S is really a new category of car in terms of its combination of power, weight and low center-of-gravity. There have been few production automobiles that put such high lateral force on wheels and suspension.


    UPDATE 2

    Here we go again. It's barely two weeks since my last torque check. After a weekend of spirited driving in my P85, I checked the lug nuts again last night. Some of them took a 20-30 degree turn to get them back up to spec. For those with track experience in a high-horsepower car, this would not come as a big surprise. But the P85 pushes the envelope further with its flat torque curve, its weight, and the large diameter 21-inch wheels. Every P85 owner should own a torque wrench and check the lug nuts at least every 60 days.
     
    • Informative x 2
  2. iadbound

    iadbound Member

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    Thanks. Good to know. That's exactly the sort of problem I might have that I wouldn't be able to diagnose. That comes, of course, from knowing almost nothing about how to maintain a car by myself. Luckily a service center is opening very close to me.:biggrin:
     
  3. GoBlue88

    GoBlue88 Member

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    Thanks for the info and the recommendation on a torque wrench. I actually went to check the torque on my wheels shortly after I took delivery, but discovered that the current wrench I own doesn't go to that high of a torque setting!
     
  4. donv

    donv Member

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    That's a good suggestion. I'm planning on swapping my winter wheels on this fall, so maybe I should invest in a torque wrench.
     
  5. Tacket

    Tacket Member

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    Yes! Under torqued wheels and under inflated tires have been issues for me with the car feeling less stable at highway speeds.
     
  6. AndreyATC

    AndreyATC Member

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    I can understand the tire inflation but the lug nuts?
    even with less torque it should not create handling issues
    i mean it's not like rims are separating from its place
     
  7. ToddRLockwood

    ToddRLockwood Active Member

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    I wouldn't have believed it either, but it seems to make a difference. I'm running 21-inch wheels.
     
  8. galangg

    galangg Member

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    Anyone with 19" experiencing something similar?
     
  9. jerry33

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

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    I haven't, but it's possible. However because the rim of the wheel is further away from the bolts in the 21" there's going to be more stress on the bolts.
     
  10. N4HHE

    N4HHE Member

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    Harbor Freight has an interesting "torque wrench converter". A load cell mounted on a 1/2" extension. If you are not in a hurry they can be found on sale for $25, currently on sale for $30: http://www.harborfreight.com/digital-torue-adapter-68283.html

    Add a 1/2" breaker bar for $10 to $13 (depending on length)
    http://www.harborfreight.com/12-in-drive-18-in-breaker-bar-67932.html
    http://www.harborfreight.com/12-in-drive-25-in-breaker-bar-60819.html

    And a 13/16" socket for $4: http://www.harborfreight.com/1316-in-x-12-in-drive-deep-wall-impact-socket-67780.html

    Then you'll be in pretty good shape.
     
  11. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN 65513, Model 3: VIN 1913

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    Very subjective but, I've started to feel a bit of "floppiness" in my car's handling in high speed turns (banked sections of freeways and such). Tesla last touched the wheels in March so, maybe, it's time I got it checked out.
     
  12. ToddRLockwood

    ToddRLockwood Active Member

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    Also, with less tire sidewall flex on the 21's, stress on the bolts is increased. If you regularly drive twisting secondary roads that are less than smooth, I highly recommend trying this. If your wheels haven't been re-torqued in awhile, you'll be pleasantly surprised.
     
  13. aaron0k

    aaron0k Member

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    This post saved me a visit to the service center. Quite a noticeable improvement after a re-torque on all the wheels. Thanks.
     
    • Helpful x 1
  14. sorka

    sorka Active Member

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    The wheel diameter with the tires is the same. I know I have both 19 and 21" wheels and they are within 1mm of the same diameter when comparing similar wear.
     
  15. jerry33

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

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    You are thinking about the tire diameter, not the wheel diameter.
     
  16. sorka

    sorka Active Member

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    ...which is what matters.
     
  17. jerry33

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

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    It matters for the drive train gear ratio. However, I was referring to the rotating mass being closer to the centre of rotation. The closer the mass is to the centre of rotation, the less force is required to turn the wheel and keep it moving.
     
  18. sorka

    sorka Active Member

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    The wheel/tire combo of the 19 vs 21 weigh within a lb of each other. The rubber with steel belts has about the same mass as the aluminum. There is zero difference in acceleration between the the 19s and 21s. I have dozens of vbox runs comparing the two at the same charge, battery temperature/power output, and air temperature.

    Now if you're talking the wider 21" on the rear with the staggered then I can't speak to that as those ARE heavier. My setup is 21" square.

    Additionally, don't you think the lateral forces applied to the wheels during turning and corning pulling the bolts are more of a factor than the sheer force applied to the bolts from acceleration?
     

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