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Speedo seems quite far out?

heap1000 Dec 4, 2012

  1. heap1000

    heap1000 Member

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    Had my Audi A3 2.0 tdi SE 2004 for a couple of weeks now, while driving on the motorway I have noticed that when I drive at 70 in the first lane it feels like I am going slower?
    Lots of cars over take me and I never seem to overtake anyone.
    I could even do 80 and it was very similar. This got me thinking that the speedo could be out?
    Last night I decided to plug the sat nav in to see what speed that gave me. I while doing 80mph on the speedo the satnav showed I was doing 72mph!
    Is this normal? Or could I have a fault somewhere?

    Thanks
     
  2. JPK

    JPK Active Member

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    What is your tyre spec?
     
  3. audicruiser

    audicruiser Audi Heaven

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    +1... Sounds like your running the wrong size tyres to be that far out.
     
  4. heap1000

    heap1000 Member

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    Hi thanks for the reply. The tyres on at the moment are

    HANKOOK ventus V12 EVO.

    205/55 ZR 16 94W

    Car is in at some point this week to have 2 new tyres.
     
  5. becks2012

    becks2012 New Member

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    If it was me can you not get a friend to follow you on the motorway to compare speeds before you start any fault finding the tyre sizes sound ok for that car
     
  6. heap1000

    heap1000 Member

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    I was thinking that myself. Will try and get someone to go down the motorway with me. Glad the tyres are ok because I have ordered 2 new ones.
     
  7. becks2012

    becks2012 New Member

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    Its not so much tyres its the wheel size i.e. 16" 17" and so on. The only way the speedo would be out is if its had bigger wheels on it and someone has re-coded ABS ecu which is possible but very unlikely I think your just driving to slow thats why everyone overtaking you
     
  8. audicruiser

    audicruiser Audi Heaven

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    The tyre size is right for 16" wheels on the A3. The speedo's will always read lower than the GPS on a sat nav, they are designed that way to help you keep your licence! Also there is an allowable 10% margin for speedo readings, so if the Sat nav says your doing 80mph and the speedo shows 72mph then it's within the tolerances.
     
  9. heap1000

    heap1000 Member

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    It's the other way round. Speedo says 80 satnav says 72. I have heard about the tolerance but did not know it was that much.
     

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