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wheel/tyre size changes- speedo incorrect??

Discussion in 'Handling' started by trekbiker, Oct 9, 2005.

  1. trekbiker
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    trekbiker Member

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    [Oct 9, 2005]
    I'm currently running 265/30/19 on a B6 avant , which i have been told by an experienced employee of ATS are 10mm bigger in overall circumference than the standard fit of 205/55/16 or 235/45/17 which would normally be standard fit.

    these wheels were fitted by an Audi dealer from new. I have 2 questions:-

    1. Would the speedo read slower than i'm actually going and by how much(is there a calculation?). would the mileage also be affected as my MPG, which i have worked out by brimming the tank against the mileage(supposedly) done?

    2. Would a smaller tyre, say a 235/35/19 be better? /ubbthreads/images/graemlins/noidea.gif

    Any help please!
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  3. sash
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    sash Member

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    [Oct 10, 2005]
    if you want the speedo to remain accurate you need to keep the rolling circumference pretty much the same.

    You can use this calculator to determine best tyre size:

    http://www.miata.net/garage/tirecalc.html
    #2
  4. trekbiker
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    trekbiker Member

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    [Oct 10, 2005]
    thats really handy, top link thanks /ubbthreads/images/graemlins/beerchug.gif
    #3
  5. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Oct 10, 2005]
    Silly question, do 265's fit on the front with no catching? and what brand tyres are they?
    #4
  6. trekbiker
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    trekbiker Member

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    [Oct 10, 2005]
    [ QUOTE ]
    Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

    [/ QUOTE ]

    no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle
    #5
  7. jojo
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    jojo S3 Drift King! Staff Member Moderator

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    [Oct 10, 2005]
    [ QUOTE ]
    [ QUOTE ]
    Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

    [/ QUOTE ]

    no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle

    [/ QUOTE ]

    Interesting, 265s seems overtyred for an A4, but if it doesn't catch.... why not huh
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  8. trekbiker
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    trekbiker Member

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    [Oct 11, 2005]
    [ QUOTE ]
    [ QUOTE ]
    [ QUOTE ]
    Silly question, do 265's fit on the front with no catching? and what brand tyres are they?

    [/ QUOTE ]

    no catching, Audi put them on as new. I have conti sport contacts and 'Nexus'(??), think the former are on front axle

    [/ QUOTE ]

    Interesting, 265s seems overtyred for an A4, but if it doesn't catch.... why not huh

    [/ QUOTE ]

    cos of the cost per corner perhaps???
    #7
  9. rojocho
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    rojocho Member

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    [Oct 16, 2005]
    try tyresave.co.uk for tyre diameters really easy, just fill in the sizes it does the rest.

    also if you have a larger rolling diameter your speedo will read slow compared to your actual road speed, not good for speed camera's! /ubbthreads/images/graemlins/beerchug.gif
    #8

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