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22 Inch Rims Question

Discussion in 'Model X: Driving Dynamics' started by dragonxt, Nov 13, 2016.

  1. dragonxt

    dragonxt Active Member

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    Tesla says the performance tires with 22 inch rims lose 10-15% range. Would opting for different tires solve the issue?
    I like the look of the bigger wheels. But I'm wondering if there is a workaround for the range loss.
     
  2. goneskiian

    goneskiian Active Member

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    There is not. It's a question of rolling resistance and lower profile tires just have more. Yay physics!
     
  3. Garlan Garner

    Garlan Garner Well-Known Member

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    I can't believe that this is true or "why" its true.

    Aside from the weight...I can't imagine how there could be such a range loss.
     
  4. vandacca

    vandacca ReActive Member

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    I may be over-simplifying it, but imagine bouncing a solid rubber ball versus a steel ballbearing with a thin rubber coating. The solid rubber ball loses very little after each bounce, while the steel/rubber ball quickly comes to a stop. All that rubber is much more effective at storing and returning energy than the steel/rubber combination.
     
  5. Garlan Garner

    Garlan Garner Well-Known Member

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    The difference between a 19 inch rim and a 22 in rim ( 3 inches ) is like a rubber ball and a steel ball covered in rubber?

    That's amazing. That's hard to believe, however I have nothing that says that you are wrong. Thanks for the information.
     
  6. goneskiian

    goneskiian Active Member

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    #6 goneskiian, Nov 17, 2016
    Last edited: Nov 17, 2016
    My apologies,
    I could be spreading misinformation (again). I've been trying to find the answer to this but it sounds like it's actually more about the mass of the wheel/tire combo that is the larger driver of the efficiency loss. So perhaps a lighter 22" wheel (than what Tesla offers) will actually be as efficient as the 20" OEM wheels.

    My misinformation here is likely coming from the bicycle tire rolling resistance information I've been reading a lot about lately where larger volume, supple casing tires roll much more efficiently than smaller tires. Anyway...

    Perhaps someone with more auto racing experience like @lolachampcar will chime in here and add some insight.

    Cheers!

    Edit: Here's one article I found that seems to back this up...

    Effects of Upsized Wheels and Tires Tested - Tech Dept.
     
  7. Garlan Garner

    Garlan Garner Well-Known Member

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    I would have expected that it was a matter of weight also. I'm having some wheels built for my new Tesla and I have the opportunity to select the weight of the wheel.
    The lighter the wheel the more susceptible it will be to damage. I'll take that over the loss of 0-60 times. However...I'm talking about a change in weight of a few pounds. I know that most would not follow my idea, however its what I want to do and I can afford it.
     
  8. Zaphod

    Zaphod Galaxy President (former)

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    Yes, this primarily has to do with the overall mass of the wheel and tire combination. Metal wheels weigh more than rubber tires obviously and larger diameter wheels typically weigh more than smaller diameter ones. At steady state highway speeds, the weight difference doesn't have that much impact. However in stop and go or city traffic, the extra weight of the heavier wheels takes more energy to overcome the additional inertia. Also, it's not necessarily the total wheel weight, it is where the weight is distributed. Larger diameter wheels will have more weight further out of the wheel diameter. More weight further out = more inertia to start it rolling.

    I would imagine a lighter forged 22" wheel compared to the OEM 22", would improve the range hit but will most likely never be as good as smaller diameter wheels. The sidewall stiffness of the 22" tires, with shorter sidewalls, also will play into the equation, but I believe the weight has the most significant impact.
     
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  9. vandacca

    vandacca ReActive Member

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    #9 vandacca, Nov 17, 2016
    Last edited: Nov 17, 2016
    @Garlan Garner , in math and physics, it's sometimes easier to explain phenomena by considering the extremes. I'm not saying that 19" and 22" rims are like rubber and steel balls, but it's easier to see/understand the effect when you exaggerate the circumstances.

    A better analogy would be two 6" rubber balls, one with an inner 2" steel ball and the other with an inner 4" steel ball. Problem is, that this image isn't as easy to predict the outcome.

    Anyway, I'm not saying that the elastic forces is the major contributor to the efficiency loss, but it definitely will play a part. As @goneskiian has indicated, weight probably plays more of a factor, and as @Zaphod correctly states, weight distribution is critical. I have a set of Cobalt RIMs (Crank Brothers) on my mountain bike that take advantage of weight distribution by having most of the weight near the axle. Makes a huge difference.

    There are also benefits with going with 22" wheels like stiffness and handling.

    Anyway, I'm waiting for a reasonably priced carbon rim to come to market. :D
     
  10. Garlan Garner

    Garlan Garner Well-Known Member

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    I agree with you concerning the weight.

    I looked at the weight of Tesla wheels and found that they are heavier than some custom wheels. Tesla wheels were coming in on average at 33 pounds.

    The Tesla Model S Wheel Guide - Tsportline

    The custom 21 inch wheels I'm having made are sitting around 35 pounds. I can't imagine that 2 pounds per wheel is really going to make any difference at all in my 0-60 times. That's only 8 pounds. 2 good lunches...I'm sitting 8 pounds heavier in the drivers seat.
     
  11. Garlan Garner

    Garlan Garner Well-Known Member

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    I wish I liked the look of dark rims.

    Now if they came out with White Carbon Fiber rims. I'm all in.
     
  12. shokunin

    shokunin P85 & S40

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    It's not just the weight but also the location of the weight. Even in a 22 vs 20 rim, there's more mass further away from the center of the axle in a 22" rim + tire than a 20" rim + tire. Wheel design might also come into play with the slipstream design being more efficient, causing less air turbulence than the 22" turbines.
     
  13. Garlan Garner

    Garlan Garner Well-Known Member

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    So which is better? Weight toward the center or weight towards the outer?
     
  14. Colby Boles

    Colby Boles Member

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    Center. The rotational inertia increases as the square of the radial distance from the center, but the mass needs to go up too considering the increased circumference and the metal being of similar thickness, so now you are talking about a cubic relationship. So, if the wheel was just a rim with no spokes, it would be (22/20)^3 = 33% more inertia for the outer part of the rim.
     
  15. Shumdit

    Shumdit Member

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    I think to minimize losses you would want to get as light of a wheel and tire and possible (the tire being more important to save weight due to the way higher inertia required to get the weigh spinning and to slow it down the further away from the hub that it is). Also keeping the tire as narrow as possible would minimize frontal area and rolling resistance vs. the same tire in wider cross section. That is what the i8 has really narrow tires for a Sports car.
     
  16. Garlan Garner

    Garlan Garner Well-Known Member

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    I agree that the narrower the tire the lest resistance, however.....I need grip in the rain. Right?
     
  17. Shumdit

    Shumdit Member

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    A wider tire does not necessarily grip better in rain. Actually the odds of hydroplaning increase with a wider tire, but there are a lot of variables (like tread design/depth, etc.)
     
  18. UnpluggedP

    UnpluggedP Vendor

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    For those looking for lightweight wheel options for Model X, check out or forged UP-02 wheels. We recently tested and found that not only are the 22" UP-02's lighter than the factory 20" wheels but 22" UP-02's with tires are lighter than the factory 20" wheels with tires as well. This is a significant accomplishment considering the weight of the larger tires. UP-02s are also available in 20" fitment and all new sets will be even lighter.

    One of our 21s for Model S for reference.

    14695354_10154760123653324_6631882582961848964_n.jpg
     
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  19. Tsportline

    Tsportline Vendor

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    • Like x 1
  20. Garlan Garner

    Garlan Garner Well-Known Member

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    That's absolutely gorgeous.
     

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