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Inside Tire Wear, my take

Discussion in 'Model S: Driving Dynamics' started by CAdreamin, Jan 22, 2014.

  1. CAdreamin

    CAdreamin Member

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    Inside tire wear is primarily caused by negative camber. Every car has a small amount of negative camber. The air suspension however increases negative camber as the MS lowers itself. (ie the wheel angle leans towards the body at the top) If you do not have air suspension then if the alignment is right, you shouldn't have excessive inside tire wear.

    If you have directional tires, they can not be swapped from left to right. With non-directional tires you can do this to get more miles from your tires.

    Also cars get knocked out of alignment if you hit chuck holes at high speed. So alignment does play a role in excessive tire wear.

    Then there is the UTG tire rating which gives you some idea of projected tire wear, ie 160-400 - the lower number being a softer rubber and wearing out faster than a higher rated tire.

    Since the MS is heavy with great torque, it is not surprising then that tires are wearing out at 7K miles.

    An AWD MS would help the tire wear issue since 4 tires gripping the road provides more tractiion and less slip. So I hope there will be an AWD MS. I understand there has been testing done on AWD MS.

    Jerry
     
  2. AmpedRealtor

    AmpedRealtor Active Member

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    Service center told me that they don't see a need to rotate my tires after 5,000 miles, and that my rear tires show absolutely no tread wear at all. Oddly, they said they could observe a normal amount of wear on the fronts, but the rears were almost like new. They did not rotate because they said Tesla policy is to keep the tires with the most tread on the rears. They told me to come back at 7,000 miles for a re-check.
     
  3. Zextraterrestrial

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    for 100$ or less you can have a set of directional tires flipped on you wheels.
     
  4. jerry33

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

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    The negative camber amplifies any other misalignment (it's not considered a wear angle in and of itself). The main cause of the excessive shoulder wear is toe. It only takes a small amount of toe out in the rear for the negative camber to try to fold the outer tire under during cornering.
     
  5. STxTesla

    STxTesla Sig #1278

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    I had to get new rear tires at 8K miles and every time that I think of this....I think about trading in my Model S for something else.

    Do you think that the software change disabling the low setting of the air suspension during lowering on acceleration will change the tire wear?
    I am somewhat jaded about the safety factor with regards to the tires....and have not been very happy with Tesla's response to the situation.
     
  6. lolachampcar

    lolachampcar Active Member

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    Less rear toe makes for more hunting on the highway (and increased range). I've tried everything from near zero toe in to 0.6 degrees of total toe in.

    There are ways to take out camber in the rear if you are willing to change parts.

    I've routinely rotated tires ACROSS the rear of a car to get the maximum life from them. Yes, this is running the outside label on the inside of the installed tire. My thoughts are I would rather have one less rain groove on the inside of the tire with 85% remaining tread depth than one more (standard) groove and 30% tread depth. I've typically done this on fun cars as I do not put up with high tire wear on my daily driver.

    Lastly, yes, MS uses the same geometry on the coil spring and air spring cars. The coil cars ride much higher than the air cars and thus camber gain for the air cars is what is causing the roughly -2 degrees of negative camber on air as opposed to roughly -1 on coil.
     
  7. wycolo

    wycolo Active Member

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    > I think about trading in my Model S for something else. [STx]

    Just trade in those 21s for 19s. Whole different kettle of fish.
    --
     
  8. mckemie

    mckemie Member

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    I rotated my 19" tires at about 25k miles when I found excessive wear on the inside rears. I eventually took it to the service center to try to get the rear suspension geometry fixed. They told me the geometry was correct and there was nothing they were willing to do to fix the un-even tire wear. They did tell me that the two wheels with worn tires, now on the front, were "bent" and suggested that I pay $1k+ for new wheels. They denied warranty replacement. I declined to replace wheels that were apparently very fragile; I don't believe the wheels had been subjected to anything other than normal pot holes. The car continues to roll VERY smoothly.

    I believe you can view rotation photos here:
    December 1, 2013
    Note that photos can be viewed at high resolution that shows wear pretty well.
     
  9. Tommy

    Tommy Member

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    As @jerry33 has correctly pointed out in a previous post, the rears are suppose to be the tires with the most tread; this is to prevent excessive oversteer from occurring if the car needed to be suddenly turned in an emergency situation. That is the reason why Costco and other tire installers will not install new tires on the front if you have worn front tires on the front and the rear tires do not need replacement. Instead they will move the rear tires to the front and put the new tires on the rear; this assumes you are purchasing just two tires.

    In 5k miles, how much of a wear difference between the front and the rear was there that Tesla felt this difference would create the oversteer problem. My worry is in your case, the front tires are wearing at a faster rate than your rear tires and the tread depth difference between the front and the rear tires is only going to become greater. That means Tesla will never rotate your tires and nether will anybody else if the difference becomes too great.

    So, measure the tread depth now and recheck every 1k miles to see if the wear begins to even out between the front and rear tires (which seems what Tesla is expecting) or if the difference becomes more pronounced. If the tread depth becomes more even than you can wait for Tesla to rotate your tires. If you see that the front tread depth is becoming less than the rear tires, it's pretty clear the tires needed to be rotated sooner to avoid the conundrum of having rotated tires with less tread depth to the rear.

    It doesn't seem like there is a hard and fast rule regarding how much tread depth difference there can be. Case in point, I have used Costco to purchase new tires and on one occasion I purchased just two tires due to a nail puncturing my front tire. I had 20k on the tires at the time. The new tires went on the rears and the rear tires moved up to the front. Costco told me to put 5k miles on the tires and I could rotate them again. The main reason to rotate the fronts to the rear is to minimize the wear pattern that develops from turning.
     
  10. lolachampcar

    lolachampcar Active Member

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    We are all knocking about the term oversteer margin (or similar). I very fun exercise is to find a big parking lot and yank the wheel from side to side as called out in FMVSS126 (Hard one way, hard back the other pausing a short bit before returning to straight) and see what your car does. I think everyone will find it plows like a pig no matter what tires you have where (within reason of course, space saver spares on the rear do not count). I think this would even be the case if you took a P+ and swapped the fronts and rears :)
     
  11. AmpedRealtor

    AmpedRealtor Active Member

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    Thank you so much for that detailed explanation. I will definitely keep an eye on things. I thought the same thing as you, however. If the tread wear continues in a linear fashion, my fronts will always be slightly more worn than my rears and the tires will never get rotated. What a conundrum! lol...
     
  12. rcc

    rcc Model S 85KW, VIN #2236

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    What are your driving habits and do you have regen set to standard or low?

    Reason I'm asking is that with 19" tires, my rear tires wore faster than my fronts. I make major use of regen braking though and while I don't hammer the car, I certainly use the power that it's got fairly often. So it wasn't a surprise to me that the rears do more work.
     
  13. wycolo

    wycolo Active Member

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    #13 wycolo, Jan 25, 2014
    Last edited: Jan 26, 2014
    @mckemie:

    "Bent Wheels" - This is measured in 'runout'. You can observe and measure this on any balancing machine. So what is that figure?

    2.5 k miles > OR < 25k miles ?!!
    --
     
  14. AmpedRealtor

    AmpedRealtor Active Member

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    I drive very conservatively compared to my other Model S owning brethren. My lifetime average is 293 Wh/mi and dropping. A few of my recent runs to town have average about 270 Wh/mi. I tend to drive with eye toward efficiency rather than performance. I use regen a lot, but accelerate rather slowly and in keeping with other vehicles. I hardly ever use the power available in the car. In that respect, I'm probably putting a lot less stress on the rears. However, there is still more stress on the rears than the fronts, which makes me curious why the fronts have more wear.
     
  15. jerry33

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

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    Check the front tires for feathering and you'll likely find that there is toe-in.
     
  16. pilotSteve

    pilotSteve Member

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    Certainly appears that wear varies greatly between our cars. Yesterday I replaced my Sig's 21" Continentals (with 19" Rial wheels/Michelan Primacy tires for winter) that have 12,600 miles on them and were rotated once at 6500 miles. Picture attached, you can see the wear is quite even and the tread wear indicators (D and W) are both visible so more than 4/32" available. Actually the rears (originally fronts) have the most tread depth.

    btw I really like the ride qualities of the Primacy's so far. Talk about "your milage may vary"!

    IMG_3376 sm.jpg
     
  17. TylerCA

    TylerCA Member

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    Happens to all of my RWD sports cars. They all wear out more in the rear.
     
  18. zwede

    zwede 2013 P85+

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    Yep. My Mustang has 11K miles on it. Front tires have about 1/2 left. Rears are getting close to the wear indicators. I'm not 18 any more, no smoky burnouts.
     
  19. AmpedRealtor

    AmpedRealtor Active Member

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    #19 AmpedRealtor, Jan 28, 2014
    Last edited: Jan 30, 2014
    Front left: -0.06 toe
    Front right: -0.04 toe
    Total front toe: -.10

    Rear left toe: .19
    Rear right toe: .19
    Total rear toe: .37
     
  20. wycolo

    wycolo Active Member

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    > -.10 front toe [AmpedRealtor]

    Jerry33 means 'excessive' front toe-in. All cars need a bit of front toe-in (negative toe value). So what is the MS acceptable range? The machine will know this - anyone? Regardless, over time your car will show feathering wear on the tread if indeed the toe is mis-aligned, along with handling issues quite possibly. If there is no feathering wear then this is not an issue.
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