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245/40/18 tyres - OK to run on the rear?

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by DALE_AVANT, May 11, 2012.

  1. DALE_AVANT
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    DALE_AVANT Avantage

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    [May 11, 2012]
    Hi guys.

    Would 245/40/18 tyres be fine for the rear on my Avant Sport? I have two spare so I may as well use them if I can.

    Many thanks
    #1
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  3. pink.teg
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    pink.teg Member

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    [May 12, 2012]
    Wat size rims are they
    ???
    #2
  4. DALE_AVANT
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    DALE_AVANT Avantage

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    [May 12, 2012]
    8J x 18".

    ET43.

    The width should not be an issue but I think the rolling radius will be out a little
    #3
  5. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [May 12, 2012]
    Rolling radius shouldn't matter on the rear, assuming your car isn't a quattro.
    #4
  6. DALE_AVANT
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    DALE_AVANT Avantage

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    [May 12, 2012]
    Nah it FWD. I meant in relation to space in the rear arches over bumps and such
    #5
  7. pink.teg
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    pink.teg Member

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    [May 12, 2012]
    In that sence ... No problems
    i have a Quattro
    and have 234/40/18 on front
    245/40/18 on rear and it's fine
    was on RR and the bloke that set up my map asked !
    and said the read out was fine !!
    #6
  8. jbcalvin
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    jbcalvin Member

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    [May 12, 2012]
    245 is the width of the tyre and will not have any effect on the rolling radius, 40 profile is right for 18" wheel, you should be fine with these, it's only 10mm wider than a normal 235....
    #7
  9. DALE_AVANT
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    DALE_AVANT Avantage

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    [May 12, 2012]
    245/40 has a larger rolling radius than 235/40, as the 40 represents a percentage of the 235/245.

    So 40% of 245 = a bigger overall tyre than 40% of 235 (iirc)
    #8
  10. PetrolDave
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    PetrolDave Well-Known Member

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    [May 12, 2012]
    #9
  11. BahnStormer77
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    BahnStormer77 BahnStormer

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    [May 14, 2012]
    FWD should be fine to run different rolling radius tyres, but you are putting a lot of completely pointless strain on the quattro differential by doing what you're doing... it'll run fine on RR or on the road, but it just works the differential constantly...
    #10
  12. pink.teg
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    pink.teg Member

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    [May 15, 2012]
    K
    will wack the 235's back on ASAP then

    Cool save them for the dry summer days ...
    #11
  13. BahnStormer77
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    BahnStormer77 BahnStormer

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    [May 16, 2012]
    other thing to bear in mind for anybody who's got FWD and wanting that hot-rod stnad with slightly chunkier tyres on the rear... it may seem really obvious, but wider tyres = more grip... so the back will grip more and increase understeer...

    One of the later model Polo GTI's (2008?) has NARROWER tyres on the back to give the car a more neutral balance on the limit :)
    #12
  14. quattrojames
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    quattrojames Moderator Staff Member Moderator

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    [May 16, 2012]
    I 'think' RS3's do too.
    #13
  15. avantsport
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    avantsport DIESEL DOG

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    [May 17, 2012]
    Will 245/40/18 on 8j et 43 go on the avant sport front and rear as i have a full set from an a6 but unsure if they will fit.
    #14
  16. archemist
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    archemist Member VCDS Map User

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    [May 17, 2012]
    they'll be about 2% bigger (RR / circumference ) than standard 215/55/16 baseline

    Tyre Calculator - Alloy Wheels - Specialist supplier of alloy wheels and tyres packages, Fast Delivery, Buy Online.

    gives you loads of option for tyre width / size.

    don't know about width (+5mm both in and out) but if people are running spacers and 35 et's then the ouside 'rim' shouldn't be a problem

    don't know about the 5mm nearer inner wheel liner though.
    #15

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