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Tire Load Index Question

Discussion in 'Model 3' started by Probllama, Oct 8, 2019.

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  1. Probllama

    Probllama Member

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    I have a set of 225/4518 XL winter tires with 95 load index in my current car and I am considering to get a LR AWD pretty soon and wanted to check if anyone knows whether I could safely use them on the Model 3? Looks like the factory 18 inch tires have 98 load index, has anyone tried to use 95 load index tires on their LR AWD Model 3?
     
  2. MountainRatMat

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    Dangerous and not recommended...you'd probably survive if you did though.
     
    • Disagree x 1
  3. Daniel in SD

    Daniel in SD Well-Known Member

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    The 20" PS4S tires have a load index of 92 so I'm guessing it will be fine.
     
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  4. Probllama

    Probllama Member

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    Oh great point, thanks! That makes me feel better about using 95 load index tires...
     
  5. afadeev

    afadeev Member

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    Here is the info on tire markings, including load index:
    https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35

    Load index of 95 corresponds to a designed load rating of 1,521 lbs per corner, or 6,084 lbs in total.
    That's about 50% above Model 3's weight.
    TM3 LR weights 3,805 lb, so technically, anything above load index of 79 (or 81 for AWD/P cars) is perfectly safe.
    Tesla Model 3 - Wikipedia

    Since you can not even buy a Michelin tire (S4, MXX4, etc) in 18+" sizes with a load rating below 84, load rating # is basically a non-issue.

    For all practical purposes, any tire of the stock diameter will always have a load rating well above the minimum for your Model 3. I can't even recall the last time I bothered looking at load ratings when shopping for tires.

    Your 225/45-18 size is going to be only -0.25" lower than stock, with -1.9% lower speedometer reading. All perfectly fine.
    Go for it!

    a
     
    • Informative x 1
  6. Probllama

    Probllama Member

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    Thanks for the explanation! I guess if you have 4 or 5 adults in the car that can add another 1000 pounds or so to the weight but that still puts it safely under the 6,084 number you calculated. I am not too happy about the slightly lowered ride height when snow/slush requires all the ground clearance you can get but I can live with quarter of an inch drop as long as I don't have to invest on a new set of winter tires...
     
  7. MountainRatMat

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    I stand corrected. So much for trusting the people at the tire shops, that was my source, They wouldn't put anything that was lower rated than stock on my car.
     
    • Like x 1
  8. afadeev

    afadeev Member

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    1/4" tire diameter drop is also a non-issue.
    If you think about it, most tires are sold with 10/32 of tread depth when new, and should be replaced when they get to wear bars at 2/32nds of tread depth remaining. That's 8/32 == 1/4" of tire height variance as an average tire tread wears off.

    For clearance, driving into a 1+ feet of snow can be a challenge. Eventually, you will start plowing it with your nose, and as snow compacts under the floor of the car, it will start lifting the wheels off the road. BTDT, not fun.
    1/4" of clearance really won't move the needle here.

    a
     

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