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Comparing new Roadster exterior dimensions to original Roadster

Discussion in 'Roadster 2022' started by ecarfan, Nov 17, 2017.

  1. ggnykk

    ggnykk Active Member

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    Michelin official specs say rear tire overall diameter is only 28.7 inch, how you get 30 inch? Remember 28.7 inch not only include the visible tire side wall, but also include the tire tread that sticks out from the tire (which you can't see or measure clearly in the picture).

    Your math is clearly wrong coz 118.75 inch is clearly outside of the range from 105.7 inch up to 114.9 inch that I defined earlier using wheel rim calculation. 118.75 inch is also 2 inch LONGER than Model S and X, which is impossible.

    That's why I use the rear wheel well as the most accurate way to doing the math here, like what I have laid out previously. I really think the wheel base fall anywhere between 110 inch to 114 inch for the new roadster. It is possible that Tesla just use the same wheelbase as Model 3 for the new roadster in length, and only make it wider in width.
     
  2. mongo

    mongo Well-Known Member

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    I got that from what a 325/35-R21 tire is supposed to be (325*.35/25.4)*2+21. I searched web for Michelin reference, but did not see one. Would be happy to correct with a reference (sure you are not thinking of 325/35 R20).
    Do you have a front diameter? In my measurement they both matched the expected.

    How is my estimating the edge of rubber on a larger measurement any worse that your guessing the tire bead seating surface on a smaller measurement?

    Why does my number not matching your number make my number wrong?

    Why is it impossible to have a longer wheelbase?

    How can you call that accurate when you are guessing what the gap is?
    I realize I may be slightly off in capturing the tread edge. However, the margin of error is <=5 pixels out of 200+ so 2.5% max. 97.5%*118.5=115.5.
     
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  3. mongo

    mongo Well-Known Member

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    I get 156 pixels for the bead seat, which comes out to 21.08 - 21.12 based on my previously measured tire sizes.
     

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  4. shokunin

    shokunin P85 & M3

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    To me, the front tire looks to be 265/35/20 and not 295/35/20 as some have reported, not sure if that affects your calcs. I don't think Michelin even makes a 295/35/20 Michelin Pilot Sport Cup 2.

    A 265 should have a diameter of 27.3" and the 325 a diameter of 28.7".
     
  5. mongo

    mongo Well-Known Member

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    I'm using 265/35/20 in front 325/35/21 in rear. But my use of tire calculators says there are 28.3 and 30 inch respectively. I haven't found manufacturer data on the rears. Where did you get those diameters from?
     
  6. shokunin

    shokunin P85 & M3

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    I've attached the spec sheet from Michelin.
     

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  7. mongo

    mongo Well-Known Member

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    Thanks. I found the problem. The post I pulled tire data from had a typo it said they were 325/35/21 but the picture shows they were really 325/30/21 which fits the data sheet at 28.7".

    @ggnykk My measurements may be off by ~4.5%. Which puts the wheelbase at around 113 and lines up with your results. Which is weird since the front and rear were in the right ratio. The render may not have the same tires? While redoing measurement in Solidworks, I noticed that the render has perspective which may be skewing things too.


    Still looks like barely enough area for 200kWh.
     
  8. shokunin

    shokunin P85 & M3

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  9. Brando

    Brando Active Member

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    computer controlled, traction control = little, if any, wheel spin [right?]
     
  10. Colasec

    Colasec Member

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    Thanks, [email protected] and friends. Can you take a shot at the height as well, please? And maybe distance from the ground to the floor pan?
     
  11. mongo

    mongo Well-Known Member

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    I'm wary to do that because the artificial perspective may give false numbers, but if I can figure out what the scale should be, I'll try.
     
  12. gregd

    gregd Active Member

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    Ground clearance is probably the next most important dimension to figure out. At first glance, the new car may have the same problem with curbs, driveways, speed bumps, etc. that make driving the current car a bit too, um, "tactile". No word if the car will have SAS or not, but I'm guessing not (for weight).

    I have a 1x6" piece of wood at the base of our downward-sloping driveway that I drive over in order to not bury the nose of the car in the garage floor as I enter...
     
  13. Carl W

    Carl W 2008, #311 thunder gray 1.5

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    I have a convoluted downhill driveway that requires me to alway enter my driveway from one direction in order to not scrape. So when I come from the other direction, I have to U-turn. I think my neighbors wonder about my sanity "did he miss his house again???"
     
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  14. Carl W

    Carl W 2008, #311 thunder gray 1.5

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    I agree that traction control will prevent wheel spin (though in the videos, sounds like the wheels chirp!). By the numbers, though, I'd think that there's 10 times more torque available than will ever be allowed to drive the car. I pity the person than turns off their traction control.
     
  15. Carl W

    Carl W 2008, #311 thunder gray 1.5

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    Thanks and I wonder if your answer "yes, that is the current assumption" should have been "yes, that is the current assumption"
     
  16. Carl W

    Carl W 2008, #311 thunder gray 1.5

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    nevermind. 10000NM is the wheel torque not motor.
     
  17. mongo

    mongo Well-Known Member

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    The overhangs on the front and rear look fairly small, may help with approach and departure angle ( just don't go over speed bumps)
     
  18. Carl W

    Carl W 2008, #311 thunder gray 1.5

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    My problem is scraping in the middle of the bottom of the car because my driveway abruptly goes downhill from the street. However, I've got my method that works, so no worries!
     
  19. CarlK

    CarlK Active Member

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    Another reason would be two separate motors are needed to conduct torque vectoring on rear wheels. Steering system took care of front wheels there is little need to add torque vectoring there. May not even be desirable to do that.
     
  20. goldface

    goldface New Member

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    Hi,
    Are there any news about the official car measurements?
     

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