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Have I made a total c*ck-up?

benjie Dec 5, 2013

  1. benjie

    benjie Well-Known Member

    Had a rather spectacular tyre blow-out today. Not fun on the M4 at 6.30am. Ive already ordered a pair of new tyres, due for fitting Friday. I've just checked & noticed I've ordered the wrong size. On the back I have 235/40/18 and on the front I will have 235/45/18 - a 5% difference in the aspect ratio. Will this have a negative effect on the car…it's quattro & I don't want to ruin the diff.
  2. DieselJake

    DieselJake Well-Known Member

    It'll knock the speedo out a bit but it's not the end of the world, ask to change for the same set of tyres though if you can.
  3. desertstorm

    desertstorm Moderator Staff Member Moderator VCDS Map User quattro Audi A4 Audi Avant Owner Group TDi

    From what I have read certainly not adviseable to run different size tyres front an rear on a proper quattro car with a torsen diff.
    Tyre Size Calculator - Legal Requirements - Etyres says there is 3.7% difference in the diameter which translates to the 235/45 tyre being 24 mm bigger in diameter than the 235/40 . So the car will have 12mm more goround clearance at the front and it will be quite noticeable i would have thought.
    The manual says all wheels should have tyres of the same make, tread pattern and size, I think thats taking it a little far.
    Other posts I have seem where people are unning staggered set ups seem to indicate a 3% difference at maximum is OK.
    As you are outside of event that and there is a noticeable difference in the size I would say don't fit them.

  4. Mike.M

    Mike.M Well-Known Member

    I would try and cancel/exchange the order with the 40 profile myself
  5. benjie

    benjie Well-Known Member

    Thanks for the input guys, just wanted to check. I'm going to replace all of them - better to be safe than sorry. I was planning on it after Christmas anyway.

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