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Increase Range by reducing Tire Width

Discussion in 'Roadster' started by lmore, Jun 20, 2012.

  1. lmore

    lmore Member

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    I wonder if anyone here has tested the Roadster range using different wheels.

    From my experience, reducing the rear wheel width from 225/45R17 to 205/55R16 increases the range as much as 10-20 %. Of course it will depend on the type of tire as well, the 205/55R16-tires I tested were winter and low-rolling resistance tires. It could also be related to the weight of the wheels, as 16" weighs less than 17". A disadvantage for the driver is that the car gets less stable and more easly drifts to the side.

    I was thinking about 135/80R15 on the front wheels and 185/60R16 rear wheels.
    Is it insane to reduce the tire width this much, will the car be impossible to drive?
    Of course this is not for high speed driving...
    How much range increase could this give?

    How much does it depend on the type of wheel keeping the width constant?
    From the rolling resistance tests I have seen, the range will change only 2 %.
     
  2. qwk

    qwk Model S P2681

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    I really doubt that the brakes will clear 17" wheels, let alone 16". 15" wheels are definately not going to work.
     
  3. richkae

    richkae VIN587

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    He is talking about the Roadster. It already has 16s in front and 17s in back. Eyeballing the brake disk and caliper it looks like you could shrink the wheel at least an inch and still have clearance.
    According to Tesla's spreadsheet, the tires provide 22% of the drag at 60mph.
    If rolling resistance is linear with tire width ( no idea if that is true ) then changing a 175 to a 135 and a 225 to a 185 would reduce the drag from the tires about 20% and increase your range about 5% at 60mph.
     
  4. lmore

    lmore Member

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    I tested at lower speeds (range 20-55 mph) and found an increases in range as much as 10-20 % just by reducing the rear wheel size as described above. I agree that testing at 60 mph could give a much lower increase. Could not find Tesla's spreadsheet, would be nice to have.
     
  5. richkae

    richkae VIN587

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  6. GSP

    GSP Member

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    I highly recommend Goodyear's Assurance FuelMax tires. They have very good performance on the Volt, and low rolling restance as well.

    GoodyearAssurance Fuel Max

    If I had a roadster I would buy them in the factory approved size. They also would be great for experimenting with smaller sizes to maximize range.

    GSP
     
  7. Pantera Dude

    Pantera Dude Member

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    A 135 tire sounds like a bicycle or dragster tire.:biggrin: It doesn't even sound safe to me? I think your car would lose a significant amont of lateral grip as well as increasing your stopping distance. It seems to me that you would be giving up a lot more than you would gain.
     
  8. TEG

    TEG TMC Moderator

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    Custom cars built to set efficiency records tend to have ultra-skinny, shrouded wheels/tires.
    [​IMG]
     
  9. TEG

    TEG TMC Moderator

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    Look closely at the super narrow tires on the VW XL1 concept:
    xl1-b.jpg
     
  10. TEG

    TEG TMC Moderator

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    Aptera prototype:
    [​IMG]


    ( Roadster was intended to have sports-car handling, so didn't go the way of extreme efficiency wheels. )
    ( They also didn't want to make a car that looks 'goofy'. )
     
  11. lmore

    lmore Member

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    Thanks for the feedback! The guys I asked at the wheel shop said it would be OK to drive using such narrow tires, but that I would not attract women ;)

    Some questions: If I get an extra set of wheels to try this, any suggestions on what to test/compare or something I should keep in mind?
    I plan to compare at higher speed 100 km/h (60 mph), as it was pointed out it is at higher speeds range is important. Also I will try to measure breaking distance. How to compare lateral grip?

    Is the bolt pattern 5x110 for both the front and rear wheels?
    I have been unoriginal wheels with bolt pattern 5x112, they seem to fit also, is that unsafe or will influence the car handling? I have asked around and searched Internet if this matters. Some (where I bought the wheels) say no, and some say yes, some say I should use "wobble bolts".
     
  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    You compare lateral grip by getting a g-force metre and running both types of tires on a skid pad. Your local auto sports club can help you with that.

    The bolts will not fully seat and will be unsafe. Use the correct size.

    Don't even think about it. ( If you go this route, be sure that your family has lots of paid-up life insurance on you)
     
  13. hcsharp

    hcsharp Active Member

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    I was wondering when the "where do I get narrower wheels?" question would come up. AFIK nobody but Tesla makes wheels that will safely fit the Roadster. And Jerry's comment about "wobble bolts" is dead right.
     

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