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Tire size for 20" wheels

Discussion in 'Model S: Interior & Exterior' started by RealSnurf, Jul 30, 2016.

  1. RealSnurf

    RealSnurf Member

    Dec 20, 2015
    SF Bay Area, CA
    I have the new TST cyclone clone 20s. Staggered with 20x9 front and 20x10 rear. TST recommends 275/40 in the back with the 20x10 wheels. I just tried to get Americas Tire to sell/install them and they only had 275/35s as the closest approved size (won't install if it's not approved). Does it matter, or should I go somewhere else that will let me buy and install the 275/40s? Will 40s be more comfortable/quiet?

  2. siraj

    siraj Member

    May 2, 2016
    Fort Lauderdale
    I have the 20" tst staggered setup with 275/40s in the back. It's super comfortable and quiet.
  3. FlatSix911

    FlatSix911 Porsche 918 Hybrid

    Jun 15, 2015
    Silicon Valley
    I would stick with the recommended tire sizes: :cool:
    Pirelli P Zero 245/40-20″ for 20×9.0″ and 275/40-20″ for 20×10.0″.
  4. randall_s

    randall_s Member

    Apr 12, 2016
    Meridian, MS
    Are you using the Pirelli P Zero? I really like the Michelin PSS, which I have on the 21's now. I'm interested in the TST 20" wheels, but I'm hesitant about switching from the PSS as well as going to a 275 width. Do you have any comparisons on performance and energy usage? You say it's quiet and comfortable. What are you comparing it to? My current energy usage is about 340 wh/m lifetime on the staggered PSS.

  5. HebrHmr

    HebrHmr Member

    Mar 22, 2015
    Can you fit a 285?

    I'm going with 245/40/20 on a 20x9 and 285/35/20 on 20x10.5 with Michelin PSS.

    The 275/40 would only be 1/2" more sidewall than the 275/35
  6. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

    Mar 28, 2015
    Houston, TX
    TST recommends a tire size of 245/40R20 for the 20x9 wheel (front), and a tire size of 275/40R20 for the 20x10 wheel (rear). I actually disagree with that recommendation.

    The standard tire diameter for the Model S is 27.7", which is a circumference of 86.9", and 729 revolutions per mile. Any tire that is fitted on the Model S should be as close as possible to these numbers, since this is what the car expects for speedometer calibration, auto-park distance estimates, and energy calculations. Ideally, the tire fitment should be within 1% of these numbers.

    The 245/40R20 tire (front, for the 20x9) wheel is 27.7" diameter (0.0%), 86.5" circumference (-0.4%), and 732 revolutions per mile (+0.4%). This is well within the 1% tolerance.

    A 275/40R20 tire is 28.7" diameter (+3.6%), 90.0" circumference (+3.6%), and 704 revolutions per mile (-3.6%). This is a fairly significant difference, and I wouldn't want to put this tire on the Model S, especially with a significantly different size tire on the front axle.

    The 275/35R20 is 27.6" diameter (-0.4%), 86.6" circumference (-0.4%), and 732 revolutions per mile (+0.4%). This is within the 1% tolerance for the original fitment tires, and nearly exactly matches the front 245/40R20 tires.

    I would fit the TST staggered setup as:

    245/40R20 front
    275/35R20 rear

    Tire rack carries several brands in this size combination. My recommendations for summer performance tires would be:

    Michelin Pilot Super Sport
    Bridgestone Potenza S-04 Pole Position
    Continental ExtremeContact DW
    Pirelli P Zero

    I think the first 3 choices are better than the Pirelli in this category.

    If you want an all-season tire, look at the Continental ExtremeContact DWS 06.
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