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Running Two Different Tyre Sizes... Help

Discussion in 'A3/S3 Forum (8L Chassis)' started by Gmac, Aug 17, 2014.

  1. Gmac
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    Gmac Active Member

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    [Aug 17, 2014]
    Needing help/thoughts...

    Looking at getting winters for the S3 8l and I've seen 2 x 225/45/18 and 2 x 225/40/18

    So I was wondering if this would be ok to run with the haldex on the S3.

    Would these calculations be correct....

    225/40 = 225mm width and side wall 40% of this so 22.5 x4 = 90mm ie 9cm for side wall (4.5 top 4.5 bottom)

    225/45 = 225 width and side wall 45% of this so 90mm + 11.25mm so 101.25mm ie 10.12cm

    So 1cm different? (.5cm top and .5 bottom

    Tia [​IMG]
    #1
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    [Sep 21, 2014]

  3. monopole
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    monopole pro-monopole-ish-ism-istic

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    [Aug 17, 2014]
    I'm sure they would be fine on different axis, but you need better advice than I could offer on this
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  4. Gmac
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    Gmac Active Member

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    [Aug 18, 2014]
    Anyone else?:uhm:
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  5. Andrew@A.L.D
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    Andrew@A.L.D Cylinder Head Master

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    [Aug 18, 2014]
    if you have traction control you will have issues
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  6. Gmac
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    Gmac Active Member

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    [Aug 18, 2014]
    Not sure what you mean? do you mean the esp or do you mean the haldex controller might not like it?
    #5
  7. snowy
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    snowy Crunching Gears

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    [Aug 18, 2014]
    The ABS unit's speed sensors will detect the axles turning at different rates and assume slip

    It might try to do all sorts to fix this - eg using brakes or more power to rear axle

    You can use any width combo, but circumferences of wheels on both axles has to be the same
    #6
  8. Gmac
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    Gmac Active Member

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    [Aug 18, 2014]
    Great, cheers snowy! I'll just get the 225/45's and keep an eye out for some more of the same! Thanks folks!:arco:
    #7
  9. kryton
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    kryton Member

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    [Aug 18, 2014]
    It goes bananas and traction control light flashes . I tried this
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  10. Alex C
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    Alex C Well-Known Member

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    [Aug 18, 2014]
    When the 225/45 are doing 62.4mph the 225/40 are only doing 60.3,mph, so one set of tyres are walking slowly away from the other pair and subsequently the Haldex works overtime
    #9
  11. RobinJI
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    RobinJI Member

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    [Aug 18, 2014]
    Sounds like you're not going to try it anyway, but just for future reference, the size calcs are correct, but that's for each side of the wheel. So a 225/40 has 9cm top and 9cm at the bottom as well.

    (I'm not sure on this, but isn't the standard S3 size 225/45r17, so surely a 225/45r18's going to be an inch too big? I'm sure someone will know.)
    #10
  12. Nick_sheep
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    Nick_sheep All The Gears But No Ideas

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    [Aug 19, 2014]
    #11

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