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8 and 9j tyre size

Discussion in 'A3/S3 Forum (8L Chassis)' started by *P3nfold*, Apr 5, 2013.

  1. *P3nfold*
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    *P3nfold* Member

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    [Apr 5, 2013]
    Hi all,

    I currently have 225/40/18 on the current 8j's on the fronts and dont really want the stretched look on the rears to match, I like having solid tyre walls.....

    Could anyone recommend a tyre size what would match the fronts on 9j's please?
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  2. Routledge
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    Routledge Wind Deflector Trend-setter

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    [Apr 5, 2013]
    245/40/18.

    HTH
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  3. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Apr 5, 2013]
    255/35/18 is nearer 225/40/18 for rolling radius.
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  4. *P3nfold*
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    *P3nfold* Member

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    [Apr 5, 2013]
    Cheers fella,

    So thats

    225/40/18 Fronts
    245/40/18 Rears

    Funny enough I was looking at a tyre size calculator at 235/40/18 for the rears, do you think there will be stretch?
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  5. Routledge
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    Routledge Wind Deflector Trend-setter

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    [Apr 5, 2013]
    True, but he said he wanted something that matched the fronts so I figured he'd want the same. :p They're wider not bigger diameter.
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  6. Routledge
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    Routledge Wind Deflector Trend-setter

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    [Apr 5, 2013]
    A little by comparison to the fronts, but it won't be mental.. Like my 225/40 on 9.5J :)
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  7. BENJAMIN
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    BENJAMIN Active Member

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    [Apr 5, 2013]
    Very important to get the rolling radius front and rear close as possible. Get it wrong and the ESP throws a fit and the haldex clutches eat themselves.

    Routledge, profile is a percentage of the width so 245/40 has larger radius than 225/40.
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  8. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Apr 5, 2013]
    Thanks you. :icon_thumright:
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  9. Routledge
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    Routledge Wind Deflector Trend-setter

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    [Apr 6, 2013]
    Whoops, I thought it was a percentage of overall diameter. So, what you're saying is that me running 225/40/18 all round with staggered fitment wheels 8.5 and 9.5 will mean my ESP will go mental and cost me loads?

    I've not noticed any change :/
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  10. BENJAMIN
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    BENJAMIN Active Member

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    [Apr 6, 2013]
    Same size tyre so difference is minimal. There is a tolerance built in to allow for say, 2 new tyres at the front and 2 worn out tyres at the back. I'd imagine yours would fall into this allowance as its so minimal.

    You can't however run 225 40's at the front and 245 40's at the back.
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  11. Sam_
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    Sam_ Down under

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    [Apr 6, 2013]
    245s fit a 9 quite well. I run them all round but 245/40/17:

    [​IMG]
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  12. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    Thanks jojo. I looked at the tyre calculator today and there is marginal difference of -0.1% which is spot on.
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  13. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    Cheers Ben.
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  14. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    Sam she looks mean!!!
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  15. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    Do you think the s3 will look ok with 9j 255/35/18 on the rears with 8j 225/40/18?
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  16. Routledge
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    Routledge Wind Deflector Trend-setter

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    [Apr 6, 2013]
    Fair play. I'll go back to minding my own business then ;)

    EDIT: I'm due to have you fix something actually.. So I expect I'll be calling you soon.
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  17. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Apr 6, 2013]
    It will look fine, but squeezing 255s under the rear arches require the correct offset. What you could do is use 235/40R18 all round I guess?
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  18. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    ET on the rims are 35, I have a rear adjustable tie arm as well so I guess I can play round with that?

    Not sure on the 235/40/18, I dont really want any stretch on the 9s.

    humm this gets you thinking lol.
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  19. BENJAMIN
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    BENJAMIN Active Member

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    [Apr 6, 2013]
    235 on a 9 will be fine mate. 255 is a little large for the arches IMO
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  20. milli
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    milli Member

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    [Apr 6, 2013]
    Im running 225 on 9.5j and it looks fine
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  21. *P3nfold*
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    *P3nfold* Member

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    [Apr 6, 2013]
    Cheers Ben again. Looking forward to our project!!

    Kool do you have pictures?
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  22. Sam_
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    Sam_ Down under

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    [Apr 7, 2013]
    Yeah I reckon 255 would be ok on the rear but it'd be pretty crucial to get the offset spot on. I have a bit of space with 245s.
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  23. milli
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    milli Member

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    [Apr 7, 2013]
    Here is my 225 tyre on 9.5j

    [​IMG]
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  24. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Apr 7, 2013]
    He doesn't want stretch, that looks stretched! Lol
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  25. milli
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    milli Member

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    [Apr 7, 2013]
    He asked for a pic, i gave him one
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  26. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    And so he did, I shall crawl back under my rock. Lol
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  27. *P3nfold*
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    *P3nfold* Member

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    [Apr 8, 2013]
    Thanks milli

    Lol Cheers jojo

    Thats too much stretch for me. I've been there and done the stretch tyres with sub 300 bhp, did not feel safe to me. So tyre on the tarmac is for winners and solid tyre walls.

    So looking at the thread, so 235/40 on the 9s only will be fine? 1.26% is the difference between tyre sizes, so that equals 8mm diameter change.
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  28. limbo118118
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    limbo118118 LORD

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    [Jun 14, 2014]
    old thread now but im stuck! just bought new wheels...

    8.5j and 9.5j.... tires already on them 225/40 all round...

    clearly back has stretch as photo above...

    this setup ok on my s3 radius ok?

    i dont know how you work it out :s any idea what tire size i could get for the rear 9.5j for a little LESS stretch!? bit much for my liking! :/ thanks in advance!!!! :)
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  29. Sam_
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    Sam_ Down under

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    [Jun 14, 2014]
    235s or 245s are what you want really on a 9 or 9.5 unless you want scene points for "sik stretch". I'm getting new tyres on Monday (AD08Rs) and going for 255/40/17 rear and 245/40/17 front.

    This is a good tool to compare sizes and rolling radius differences:
    Visual Tyre Size Calculator | Kouki Tech
    I don't pay too much attention to the visual representation of the actual tyre size as it's a little off.
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  30. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Jun 15, 2014]
    If the tyre sizes are correct front and rear, then the rolling radius should be correct irrespective of stretch on the sidewalls?
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  31. CHRISTOPHÉ
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    CHRISTOPHÉ Member

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    [Jun 15, 2014]
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  32. limbo118118
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    limbo118118 LORD

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    [Jun 15, 2014]
    Tryed reading up loads on if tonight but iv can sit the wheels next too each other and the front sits higher and it has less stretch so would of thought that would of made a difference?
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  33. jojo
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    jojo Looking for Boost! Staff Member Moderator

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    [Jun 15, 2014]
    Fair enough, I walkways thought the stretch was in the sidewalls, it cam compress the tread area aswell to reduce the rolling radius. Another reason for me to never go with stretched tyres, as they are clearly not designed by the manufacturer to be used in such a form.

    Don't get me wrong, I have nothing against stretched tyres, but I just think I prefer my car, with it's 270odd horses to be unleashed on proper fitted tyres.
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  34. limbo118118
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    limbo118118 LORD

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    [Jun 15, 2014]
    Yeh i feel the same abit why im after a set of rear tyres for 9.5j's to fit with abit less strectch! Any idea how you calculate the rolling radios % out?
    #34

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