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Different tires and wheels? Lower profile? Wider? Taller?

Discussion in 'Roadster' started by TEG, Jun 19, 2007.

  1. TEG

    TEG TMC Moderator

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    #1 TEG, Jun 19, 2007
    Last edited: Apr 19, 2010
    Over the years, the sizes and aspect ratios of tires has changed quite a bit. Isn't there one school of thought about how to do it right? Apparently not, as it appears to be "fad driven" to some extent.

    Just as a quick example, sports cars of the 1950s/60s/70s tended to have what we would consider (by today's standards) small wheels and very high profile tires.
    [​IMG]

    These days you find that sports cars have much bigger OEM wheels with much lower profile tires.
    [​IMG]

    These changes were gradual rather than sudden. Customizers have tended to do aftermarket resizing which sets a trend that the factory eventually follows.
    Aftermarket tire and wheel shops advertise "plus" packages to get larger wheels.
    http://type2.com/library/tires/tirefaq.htm
    "3.D. What's a Plus One, Plus Two or Plus Three conversion?
    Also shown as +1, +2 or +3, these designations indicate switching from stock rims to rims of 1, 2 or 3 inch larger diameter. Going to a larger diameter rim while keeping overall tire height about the same can allow for a significantly wider, shorter tire which can have a dramatic effect on a car's handling, ride and appearance. "

    For various reasons the manufacturers tend to say that they do not recommend or endorse these changes, but people go ahead and do them anyways. For instance, on old muscle cars it is typical to find them lowered, with much larger (than stock) wheels and much lower profile tires.
    [​IMG]

    I have heard some people say that doing the "plus" conversion is a good idea because the factory is overly conservative for reasons that don't really matter.
    For instance, they think:
    * Wheels are smaller than they need to be so snow chains can be fitted. (Yet I never drive the sports car in the snow.)
    * Wheels are smaller than they need to be because the factory was trying to save money. ( Yet I want to spend extra money to improve my car. )
    * Tires are higher profile than needed so they can absorb speed bumps. ( But I always drive slowly over speed bumps. )
    * The car is higher than it needs to be to meet USA headlight and bumper height standards, but the European version is lower (as it is "meant to be") so we should fix the problem.

    So given those sort of thoughts, are the Roadster tires and wheels already "perfect", or would someone be incllined to try to improve them with aftermarket parts?
    The market for aftermarket wheels is HUGE. Sometimes people change them just to have a different style, but could there be room for improvement?

    When lowering or changing tires sizes it is common to introduce problems that weren't there with the factory package. Common problems include:
    * Improper speedometer calibration.
    * Improper brake dive calculations for headlight leveling and/or electronic brake force distributions controls.
    * Heavier and/or less strong wheels (are they forged?)
    * Improper alignment
    * Rubbing / scraping
    * Excessive road noise, or vibration

    Is this an improvement?
    [​IMG]
    [​IMG]


    =================================================================

    For reference, the Roadster's OEM wheels are
    Front=175/55 R16
    Rear=225/45 R17
    [​IMG]
     
  2. tonybelding

    tonybelding Active Member

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    Also they were narrow by today's standards. I remember when I was looking at cars in the mid-1990s and being impressed with how wide tires had become, compared with the older cars. But I think it's one of those trends which has probably now been carried beyond the point of common sense.

    I tend to be very conservative in these matters.

    For example, in the almost two years I've had the Esprit V8, I've done nothing to it -- no customization at all, not even a "chip" for earlier boost and increased torque, which many Esprit owners tell me is a must-have upgrade. Well. . . I did a little research, and it turns out the transmission on the older cars can't handle as much torque, that's why the Lotus engineers programmed the chip the way they did. If you upgrade the chip, then you risk damaging the transmission, or else you have to upgrade the transmission components too, and then it becomes a much more expensive and involved project.

    I can understand the guys with the relatively cheaper and lower performance cars, like a Miata for example, wanting to bolt on a supercharger or something like that. But if you already have a $100,000 supercar in your garage, I reckon there's little to gain by second-guessing the engineers who designed it.

    Regarding tires and wheels. . . I don't see anything wrong with the Roadster's wheels, they look good to me. The tires are Yokohama Advan Neovas, they're possibly the most advanced tires available for a sports car. Why fix something that isn't broken?
     
  3. danny

    danny Administrator

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    One of the issues is making sure you have a good match of tire width in the front with the width in the back.
    If you look at most sports cars, they tend to have wider tires in the back. If you make tires wider without thinking about the technical side that the factory thought about, could you possibly introduce handling problems? I'm not sure of this, but i think based on the drivetrain and the weight distribution, you need a certain ratio of front to rear tire width. This can be calculated i believe by people who have far more idea of what they are talking about then i do.
    This also applies to brakes, I believe you can negatively affect brake performance by just going for some random bigger size discs. You need to get a certain ratio of front to back. Does this make sense to you? its easier to explain with a car infront of me.
     
  4. danny

    danny Administrator

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    Tony, i don't think hes talking about changing the brand of tire, rather the width and sidewall of the tire.
    Would wider tires on the roadster not give it more grip and there for better performance?
    I think yes, but there was obviously some engineering and balance decisions that had to be made.
    My guess would be that they are the size they are for a reason.
     
  5. TEG

    TEG TMC Moderator

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    #5 TEG, Jun 19, 2007
    Last edited: Apr 19, 2010
    I went though the whole process a while back with my 1st gen Rx7 Autocross car.

    The car started out with 185/70R13 tires all around which seem to be rather high profile for a "sport car".
    When all was said and done, I ended up with 285/45R15s in the rear, and 225/50R15s in the front.
    It was quite a transformation, but I think I had overdone it on the rears. I ended up with fiberglass "IMSA" style body flares on the back to fit the big tires.
    (I started out with Pirelli P7 tires, then Yokohama AVS intermediates)


    The car had tremendous straight line and lateral grip, but I got this feeling like I was dragging the rear end around with me everywhere I went.
    The 350hp 13B propane turbo was good fun to power slide the rear end through corners, but it wasn't very competitive time wise to do it that way.

    Since then, having driven many other cars, and having a penchant for mid engined two seaters, I have come to the conclusion that the best handling cars have near 50/50 weight distribution and the same size tires on all 4 wheels.

    By the way, as has been stated, if you upgrade one thing you may find the limits of other parts.
    After I added the bigger tires and more powerful engine then I ended up breaking the rear differential a couple of times before buying a race part instead. The race part was rather noisy so wasn't very pleasant for street use.
    Also, the brake system needed to be upgraded to deal with the higher speeds and performance.
    (Amazingly the stock 5 speed transmission held up with 3x power and torque without a problem).
     
  6. W8MM

    W8MM R1.5 #325 + Mdl S #01380

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    After doggedly and unsuccessfully trying to outsmart car designers all through my youth, I now find it very amusing to watch others try it today.
     
  7. AGR

    AGR Member

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    First blush the Roadster's wheel and tires are on the small side. The front one are quite small probably due to the lack of a power steering, and to make it somewhat easy to park the car.The rear one are almost acceptable.

    They are the same size tires from the Lotus Elise which weighs quite a bit less.
     
  8. TEG

    TEG TMC Moderator

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  9. tonybelding

    tonybelding Active Member

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    To me those custom wheels don't look any better than the originals, or even as good. I really like the factory wheels.

    If I were going to make any changes to the wheels, it would more likely be some sort of dorky-looking but aerodynamic wheel cover.

    BTW, isn't it odd how the same car can look so different -- I mean the color -- in two different photos?
     
  10. TEG

    TEG TMC Moderator

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    Yeah, that first photo looks too pink.
    Color and white balance can differ a lot from camera to camera.
    (Some of it might be user error on the settings, and some might just be camera differences).
     
  11. neo914

    neo914 New Member

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    IMHO the Tesla roadster is a big improvement to the 2nd generation Elise design but could use something to make it stand out in the supercar arena. Larger diameter wheels and lower profile tires can enhance the look and improve performance. A taller and narrower (low rolling resistance) combination should even improve mileage. If anything they should have the lightest wheels available.

    There's high demand for wheels & tires which is why SEMA devotes a building to them. Of the many wheel designs, there are very few designs that stand on their own. Notable designs are Porsche Fuchs, BBS basket weave, Mercedes AMG monoblock, and some of the newer BMW wheels. Personally I would like to see a wheel design that mimics the electric motor rotor and windings.

    The collectors and conservative owners won't deviate from stock but the performance and youthful minded owners will likely want 18's or 19's maybe larger if they can be made to fit with the suspension height and other aspects compensated.

    My guess is the factory engineers have leveraged the Lotus specs and haven't had the time or need to test other sizes and components. If it's ever raced, more sizes will surely be tested. Maybe the factory or an independent group will create a "tuning" company that will offer more options in the future...
     
  12. Kardax

    Kardax Member

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    neo914, there's a certain balance to be obtained. Sure, you can put 19" rims on a little car like this, but you're probably making tradeoffs in ride comfort and handling if you do.

    Efficiency is important for the Tesla Roadster, but equally important is performance. This is a $100,000 sports car; it needs to drive like one if they want to break out of the rich greenie niche. This is why they're going through all the pain of developing their own transmission, using sport tires, and making aerodynamic compromises to keep the look good.

    -Ryan
     
  13. TEG

    TEG TMC Moderator

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    In NYC (I think):

    2332064692_26c7578dff_b.jpg
     
  14. Hunter

    Hunter Member

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    hmmm

    Wasn't there a bunch of talk a year or more ago concerning the wheel/tire design and how it was a carefully-selected balance between rolling resistance and handling performance? Seems like you could trade one for the other, but I'm guessing the Tesla engineers have already chosen what they consider the "sweet spot." On the same note, I doubt they got Yokohama on board for a new tire design without appropriate size/aspect choices.
     
  15. siry

    siry Member

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    same tires (yoko advan neova), same tire and wheel dimensions, different wheels (aftermarket testing) in this shot. These wheels are forged aluminum like the stock wheels but look different and are lighter. They are being testing for durability.
     
  16. TEG

    TEG TMC Moderator

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    I like the looks of them more than the stock wheels, although black isn't necessarily the best finish to go with all colors.

    It would be nice if they were offered in a "gun metal gray" color.

    DSCN0106.jpg
     
  17. doug

    doug Administrator / Head Moderator

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    Some info about these wheels posted on Lotustalk:
    2332064692_26c7578dff_b.jpg
     
  18. malcolm

    malcolm Active Member

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  19. graham

    graham Active Member

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    Sigh... It is obviously too early in the morning and I haven't had caffeine, yet. I read this as: "Edison-specific wheel design" and said out loud to my computer: "There is no way they called it that!" After pouring over the linked pdf, I finally figured out my mistake...
     
  20. vfx

    vfx Well-Known Member

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    I carefully read the quote:
    As a bit of hyperbole since we here all know that unlike other manufactures, there is no distinction between Tesla and Dealers.
     

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