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Tyres! i need the FACTS not the opinions.

Discussion in 'A3/S3/Sportback (8P Chassis)' started by JJ.Foulds, Apr 16, 2013.

  1. JJ.Foulds
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    JJ.Foulds Well-Known Member

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    i cant seem to find a solid answer on the interwebs so here goes...

    Right... tyres on the A3, standard is 225/45/17 correct? now as far as i understand with the naked eye 245 is a wider tyre. the wheel size would be 245/40/17 which would be overall slightly smaller but mostly the same.

    Now am i right in thinking a 245 has more grip over a 225, obviously of the same tyre?

    So if the answer to the above question is YES, how does the SIDEWALL affect grip in a straight line? or while cornering? or is the sidewall still big enough at /40/ to not make a difference?

    Ok second set of questions.
    Why doesn't everyone have the widest tyre they can fit for better grip and just general safety? (what do the high powered S3's run?)

    Quattro Haldex and the use of a different sized tyre on the rear. Would this mess things up when the quattro kicks in and even show a decrease in grip? or would it not make a difference.

    And finally.
    Im guessing i can easily fit 245/40/17 on the rear with no rubbing problems, but what about the front, should i leave them as 225 in a perfect world, or would the same size also fit the fronts?

    And how can i tell if the 17" rim would support the 245?

    I apologise for the mass of questions, but its something that really has baffled me.

    Thanks alot.

    JJ.
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  2. sliced
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    sliced Drive safe, stay alive.

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    I don't get it, are you running a stretch ATM?
    Putting 245 would surely make a bulge in the middle of the tread as its gonna pinch the sidewalls if you put oversized tyres on a wheel
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  3. JJ.Foulds
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    JJ.Foulds Well-Known Member

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    I realise this might sound stupid bit im a newb and a bit confused lol
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  4. B5NUT
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    B5NUT Well-Known Member

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    What ever you do don't run different size tyres with Quattro.
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  5. olethalb
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    olethalb Member

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    use the miata tyre calculator to work out rolling radius

    40 is not a measurement more of a ratio or percentage so a 40 sidewall on a 225 will be taller than a 40 sidewall on a 205 for example
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  6. olethalb
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    olethalb Member

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  7. olethalb
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    olethalb Member

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    also regards grip best options to get more grip is to have a decent brand tyre, correct pressures and 4 wheel allignment - not forgetting general condition of suspension components and bushes.

    you'll be wasting your time fitting a set of contis if your geometry is out, may as well get some wanli :D
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  8. JJ.Foulds
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    JJ.Foulds Well-Known Member

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    Right ok, thanks for that.! Has been a help, normally i stick with eagle f1 aso's so all shud br good there.

    JJ
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  9. box500
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    box500 Member

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    Wider tyres do not always mean extra grip !

    It's more to do with the size of the contact patch, pressures, tyre compounds etc etc
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