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Staggered alloys and tyres?

Discussion in 'A3/S3 Forum (8L Chassis)' started by Swervedriver, Jul 30, 2014.

  1. Swervedriver
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    Swervedriver Member

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    [Jul 30, 2014]
    Been offered a set of 8 and 9 x 18 alloys, with 225/40/18 tyres all round, to go on my S3 8L. Two questions, is the 225 a bit stretched on a 9 inch rim, and because of the stretch, will this reduce the rolling radius of the rears, and cause any problems with the 4wd?

    Regards

    Craig.
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  3. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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  4. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Jul 30, 2014]
    According to tyre fitment calculator tuffty posted up, the width of the rim has no effect on tyre circumference(on the basis the tyre fits on), so is the calculator flawed or correct? lol

    Online Wheel and Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit
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  5. 45bvtc
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    45bvtc Well-Known Member

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    [Jul 30, 2014]
    No Craig, you've a Haldex 'Quattro' system, so there'll be no problems with the 4wd.

    Had you a Torsen 'Quattro' system then yes, you'd certainly develop problems.

    A for the tyres, a 7.5 to 9J rim is recommended for a 225/40/18 tyre.

    However, consider the Audi RS3, this car has 235/35 fronts and 225/35 rears on 19-inch/8J rims and that's the Audi STANDARD.

    However, on my RS3 I'm using 255/30 fronts and 225/35 rears on 19-inch/8.5J front and 19-inch 8J rear rims, and that's the Audi OPTION for the RS3.

    NOTE: The RS3 has bespoke carbon fibre front wings to accommodate the 'larger' front wheel and tyre; your S3 8L will not have that same arrangement so take care.

    Hope this helps...:thumbsup:
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  6. 2.8 30v
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    2.8 30v Member

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    [Jul 30, 2014]
    Is that right your running wider wheels at the front
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  7. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 30, 2014]
    Haldex or no haldex... the rolling radius needs to be more or less the same across all four wheels else it messes about with the ABS sensors which in turn effects ESP and Haldex operation...

    Audi used different width wheels on the TTS QS... 8" front and 8.5" rear and used 235/40/18 tyres...

    225's are possibly a little on the stretched side for 9" rims and could alter the final rolling radius...

    <tuffty/>
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  8. Swervedriver
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    Swervedriver Member

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    [Jul 30, 2014]
    Thanks for the replies guys. Tuffty, would the rolling radius be much different, than say, a pair of half, or part worn tyres on one axle, and a new set on the other?
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  9. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Jul 30, 2014]
    Don't know without measuring them....

    tbh its a bit out of my realm of experience... never personally done it some can't really comment other than I know that if one axle reads xx different to the other axle the ABS unit would start throwing implausible signal faults which switches off things like ABS, ESP and haldex control on quattros... what the tolerance is exactly I don't know..

    You could be ok but generally speaking the 9" ones will be a smaller rolling radius to start with on the same size tyre so tyre wear may tip it over if you are bringing it too close to its tolerance...

    <tuffty/>
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  10. 45bvtc
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    45bvtc Well-Known Member

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    [Jul 30, 2014]
    YES... :drag: And for 2-years now...

    8.5J fronts with 255/30s and 8J rears with 235/35s, superb ride and handling...

    And here's the difference between an 8.5J with a 255/30 and a, 8J with a 235/35: BOTH are Audi STANDARD for the RS3:

    [​IMG]

    GO Audi RS3...:eyebrows:
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  11. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Jul 31, 2014]
    The thing is John, Audi would have calibrated the RS3 Haldex to run those size tyres/rolling radius. On an 8L, the Haldex allows a 2% rolling radius difference to accommodate tyre wear, before it thinks it's slipping, and kicks in.
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  12. 45bvtc
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    45bvtc Well-Known Member

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    [Jul 31, 2014]
    Thanks jojo, I didn't know that.

    Such a GREAT forum audi-sport is as there is so much knowledge available.

    Thank you... :hi:

    For the record, here's the RS3 setup:


    [​IMG]
    Last edited: Jul 31, 2014
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  13. Swervedriver
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    Swervedriver Member

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    [Jul 31, 2014]
    Couldn't agree more.
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  14. Swervedriver
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    Swervedriver Member

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    [Jul 31, 2014]
    Couldn't agree more.
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