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Negative Camber and Tire wear on MS

Discussion in 'Model S: Driving Dynamics' started by dbw77, Sep 6, 2013.

  1. dbw77

    dbw77 Member

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    Since I am relatively new here, I am not sure if this was discussed before, or may have already been quoted before as well.

    I see a lot of discussions about negative camber, and excessive or early tire wear, especially on the 21" (which I am getting on my MS)... So I was trying to research "negative camber and tire wear" I came across this, which I find interesting, especially about the aggressive v.s. conservative cornering having an effect on tire wear (I thought it would be the opposite).

    So I am wondering, for those who have suffered from excessive early tire wear, was it because of misalignment issues, or do you know if cornering aggressively or conservatively had any impact?


    "Since street suspensions cannot completely compensate for the outer tire tipping towards the outside when the vehicle leans in a corner, there isn't a magical camber setting that will allow the tires to remain vertical when traveling straight down the road (for more even wear), and remain perpendicular to the road during hard cornering (for more generous grip).
    Different driving styles can also influence the desired camber angle as well. An enthusiastic driver who corners faster than a reserved driver will receive more cornering grip and longer tire life from a tire aligned with more negative camber. However with the aggressive negative camber, a reserved driver's lower cornering speeds would cause the inside edges of the tires to wear faster than the outside edges.

    What's the downside to negative camber? Negative camber leans both tires on the axle towards the center of the vehicle. Each tire develops an equal and offsetting "camber thrust" force (the same principle that causes a motorcycle to turn when it leans) even when the vehicle is driven straight ahead. If the vehicle encounters a bump that only causes one tire to lose some of its grip, the other tire's negative camber will push the vehicle in the direction of the tire that lost grip. The vehicle may feel more "nervous" and become more susceptible to tramlining. Excessive camber will also reduce the available straight-line grip required for rapid acceleration and hard stops."

    From: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

     
  2. JPP

    JPP Active Member

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    ...if you search out lolachampcar (many posts here and on TM forums), he has lots of real world experience and expertise (former race car driver) and has lots of insight into this...
     
  3. texex91

    texex91 Banned

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    I'm more interested in what Tesla has to say, and what they are doing to make sure we get as much life out of our tires as possible.
     
  4. dbw77

    dbw77 Member

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    Thanks for that, I will take a look...
     
  5. SCW-Greg

    SCW-Greg Active Member

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    Well there's tire wear, and then there's car handling performance - with an emphasis in safe handling in a crisis. They don't always go together. BMW and others use this same approach to prevent oversteer in an emergency... at the sacrifice of tire wear.

    Not necessarily the answer we want to hear... but as JPP mentioned above, there's quite a lengthy discussion about this: Negative Camber in the Rear and Expensive Tires
     
  6. texex91

    texex91 Banned

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    #6 texex91, Sep 6, 2013
    Last edited: Sep 6, 2013
    I understand Greg. I've owned many a high performance cars, and never heard of 5K serious tire wear with regular driving (as you noted in another post). This is begging for a class action lawsuit if they don't fix it.

    I sure hope I don't have any problems--and if I do they replace the tires at their cost with as many issues that have been reported. I've owned many 911's, and none of these issues. So the 'oh it's 21's' doesn't cut it.

    They sell them, they need to back it up or tell prospective buyers in on the website--"IF YOU BUY THIS CAR WITH 21's YOU MOST LIKELY WILL NEED TO REPLACE WITH 5000 miles". Definitely not arguing, just saying, I smell some serious legal issues if this does not get cleared up ASAP.

    People spending $100K won't put up with this--I certainly won't.
     
  7. Jason S

    Jason S Model S Sig Perf (P85)

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    For the 21" Contis, 10000 miles is more normal wear from "correct" aligned rear tires. The 5000 mile ones tend to be badly aligned for one reason or another.

    And 20000 miles from front tires seems normal to me.

    The PS2s wear faster tho.
     
  8. texex91

    texex91 Banned

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    #8 texex91, Sep 6, 2013
    Last edited: Sep 6, 2013
    I think the big question is what is "correct" when it comes to alignment? Not sure the Tesla SC know. Who else would have answers?

    Seems like Greg only got 5K miles with normal driving. So just curious if we could get a definitive answer from Tesla on 21's, and do their SC know how to align correctly? That was a question I don't know.

    Bottom line I love the car (can't wait for it to arrive) and spent $115K, just trying to get this resolved.
     
  9. lloyds

    lloyds Member

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    I have 4k on the odo and starting to see slight wear on the inners of the rear. Perhaps another 4k and the tires will have to go. :(
     
  10. FlasherZ

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

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    Mine took 9,500 miles with proper rotation. The inside shoulders of the rear tires get about 4,500-5,000 miles without rotation.

    I was informed by the service center that the alignment specs have changed compared to how some of the oldest cars came off the line.

    I have heard recently that Tesla may be issuing a "kit" to adjust things a bit, given the number of cases they're seeing. Was told to hold tight.
     
  11. SCW-Greg

    SCW-Greg Active Member

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    While I had mine rotated today, and the rears had 4/32 left, now that they're on the front, I expect (with less aggressive driving) I should get another 5k+ out of all 4 of them. We'll see.
     
  12. brianman

    brianman Burrito Founder

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    Three not-very-random data points on the OEM Conti 21s:
    1. my P85, replaced at 8,500 mi (user-inflicted wear w/ 50 autocross laps in one day didn't help)
    2. friend with 85, replaced at 19,000 mi
    3. forum member that I met in person at a Tesla event, 23,000 miles and tires aren't even ready to be replaced yet

    YMMV.
     
  13. kvietor

    kvietor Model S S280 VIN 168

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    13000+ miles, rotated once. 7/32 left on all tires. 21" continentals.

    IMG_0912.JPG
     
  14. Sundy

    Sundy Member

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    Lolachampcar did an informal survey about tire wear, and there seems to be a lot of variability. I wouldn't assume 5000, nor 20,000. For most with 21" wheels, the answer seems to be somewhere in between. Downside of the P+ is you can't rotate back to front, but the stiffer suspension might be a positive.

    Look for the thread with this title:

    Thread: 19" and 21" Tire Wear (informal) Survey
     
  15. SCW-Greg

    SCW-Greg Active Member

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    Well your 7/32 look a lot like my 4/32 (which have now been rotated to the front)...

    image.jpg

    I'm thinking I still got some miles left on them.
     
  16. texex91

    texex91 Banned

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    Okay, looks as though 5K-10K. I am glad per one post that Tesla does know there's an issue. As stated above the + you cannot rotate, so keeping perfect alignment, etc is important I would assume.

    All looks okay and the world is indeed not ending (as long as Tesla fixes :biggrin:)
     
  17. lolachampcar

    lolachampcar Active Member

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    Tesla made a conscious decision to run the same suspension geometry on the coil spring and air suspension cars. In doing this, they knew rear camber in Standard ride height on air suspension cars could go as high as -2.1 degrees. This will increase to somewhere in the -2.5 degrees in low mode when the car is on the freeway. It is designed into the car on purpose and it will require a conscious decision on Tesla's part to change that. WRT the "my 911s do not do this" comment, I've dealt with many a 911 with lowering springs that had to have GT3R lower arms to stop them from shredding rear tires in 4K miles so, yes, 911s have this issue when they have been mucked with.

    There is a huge disparity in wear which does not seem to be directly tied to driving style. There are aggressive drivers who report good wear while some very mild drivers are getting hammered. There have been reports of excessive toe (both in and, if you can believe this, OUT). As Jerry would say, camber is not a wearing suspension angle but it will amplify any other alignment issue. Given the wide disparity in wear, it is advisable to watch your rears closely and head things off early before you loose a set of tires.

    My current guess is that coil spring cars will not see a problem at all. I've not put a camber gauge on my wife's car but my eyeball tells me the rear is around -1 degrees of camber. Air cars are lower in Standard mode then the coil spring cars and lower further on the highway. These are the cars that will see very high negative camber values and thus be subject to possible high wear. Stiffer, wider profile 21s are less compliant and thus more susceptible to the wear issue. Rear toe set anywhere near the maximum allowable toe in will be prime candidates.

    The above is just a guess on my part. The data points this direction but the sample size and follow up is not sufficient to form concrete conclusions.

    My P85+ is lowered 1/2" from stock and the links allow around -1.2 degrees of negative camber at Standard ride height (which is within Tesla's allowable range for coil spring cars). Wear is even across the back at 2500 miles and I expect to rotate the tires across the back at 7500 for a total life of 15K. I consider this acceptable for the weight of the car and my driving style (315 WHr/mile lifetime).
     
  18. texex91

    texex91 Banned

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    Yes, well I didn't 'muck' with my 911 tires, and they were fine. Anytime you muck with something it will probably mess something else up (especially if not factory spec).

    However, the rest of your post makes complete sense regarding the air suspension and explanation as to wear because of it. Hummm, makes me wonder if I should have stuck with just P85 no air? NA! I want something closer to my 911's handling and suspension wise, so I guess I will just have 'pay to play' on tires.

    Good reply and info. Just curious how are you going to rotate back tires across?
     
  19. lolachampcar

    lolachampcar Active Member

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    My logic on rotating across the back (dismounting and remounting the rear tires) is that I would prefer one less rain groove with 80% of the available tread depth then the extra rain groove with 30% depth. The relative tread depth numbers and rotation time frame were determined by trial and error from my Maranello and may not be the exact ones for MS. The directional nature of the tires is tied to the rain grooves only and I have had great success in the past running tires "inside out". That being said, this practice does fall under the mucking with it category (along with lowering links and upper suspension/camber arms) and should probably be done with thought if at all.
     
  20. Blurry_Eyed

    Blurry_Eyed MS Sig #267, MX Sig # 761

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    #20 Blurry_Eyed, Sep 7, 2013
    Last edited: Sep 8, 2013

    Perhaps the wide disparity in tire wear has to do more with the type of driving (vs. style) people are doing. Since the Air suspension cars in low mode increase the negative camber, if someone is doing the majority of their driving that engages the low mode, might that negatively impact their tire life? Also if a subset of those cars were initially out of spec with respect to the camber and other alignment factors to begin with (Or in spec, but at the boundary of spec - which I believe can be up to -2.15 degrees of camber for example) that in combination with the increase in negative camber in low mode could be a factory that could help explain the wide disparity in tire wear?

    For example, my wife is the primary driver of our Model S. We are at about 15,500 miles on our original set of 21" Continentals. We have them regularly rotated (Did it at 6,500 miles and at 12,500) and have made sure the alignment is spot on. The type of driving she primarily does is city driving. I'd say the mix is probably about 90% city (Standard suspension mode), 10% highway (Low suspension mode). I don't have the tread depth readings, but the alignment shop we go to noted the wear on the inside of our tires as soon as 6,500 miles but our tires have held up well since their first visual inspection at 6,500. If we are lucky, we may end up getting close to 20,000 miles out of this set.

    Just some thoughts that I had after reading lolachampcar's post.

    ======

    Update - I just curbed the wheels while driving (9-7-2013 & my wife wants me to make sure people know it was me that did it and not her!) and damaged the sidewalls - about a 2 inch straight cut on the FR and a quarter sized gouge out of the tire on the RR. I'll probably have to end up replacing them both. I'm taking the car in on Monday to have things looked at...
     

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