Author Topic: Tyre size can it affect speedo reading  (Read 3124 times)

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  • Offline Dachley

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    Offline Dachley

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    Tyre size can it affect speedo reading
    on: Apr 30, 2018, 05.16 pm
    Apr 30, 2018, 05.16 pm
    My speedo is ridiculously out , reading 78mph at actual 70, but Honda says it is in spec. So with some new rubber due soon was looking at getting 150/80/17 at the rear instead of 150/70/17 which will give about 15mm extra wall height and 30mm diameter which hopefully will bring speedo closer to actual. What are people’s thoughts on this?

  • Offline scotsy

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    Offline scotsy

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    Re: Tyre size can it affect speedo reading
    Reply #1 on: Apr 30, 2018, 06.25 pm
    Apr 30, 2018, 06.25 pm
    Just learn to live with it like the rest of us, its no big deal to knock roughly 10% off whatever is showing. Those who ride with satnavs in view tend to use the GPS speed anyway as a guide.

    As a sidenote most Jap machinery (including cars) tend to read up to 10% fast (as they are allowed 10% by law)

    There are devices you can buy called 'speedo healers' if you feel the need for accuracy though.

    Ian  :305:

  • Offline Dachley

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    Offline Dachley

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    Re: Tyre size can it affect speedo reading
    Reply #2 on: Apr 30, 2018, 07.19 pm
    Apr 30, 2018, 07.19 pm
    I know what you mean but after returning to Honda after quite some time of Yamaha and Ducati bikes where they were pretty accurate I would prefer it to read right. Not sure what handling effects changing diameter may incur and wonder if anyone else has tried this.

  • Offline Maverick

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    Offline Maverick

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    Re: Tyre size can it affect speedo reading
    Reply #3 on: Apr 30, 2018, 07.27 pm
    Apr 30, 2018, 07.27 pm
    Yep, std Honda error....

    I would expect the speed is calcluated by gears and shaft rather than wheel rotation

    Satnav, speedo healer or change back to your other bikes.

  • Offline scotsy

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    Offline scotsy

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    Re: Tyre size can it affect speedo reading
    Reply #4 on: Apr 30, 2018, 08.58 pm
    Apr 30, 2018, 08.58 pm
    My Nissan car was exactly 10% fast also


  • Offline navigator1946   gb

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    Offline navigator1946

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    Re: Tyre size can it affect speedo reading
    Reply #5 on: Apr 30, 2018, 10.23 pm
    Apr 30, 2018, 10.23 pm
    My CT is also just less than 10% out, and it bugs me. Did reduce a bit when I replaced the original Battlewings with Metzeler Tourance tyres.  But as others have said, you get used to it.  Ironically, my Deauville was accurate to 1 or 2 mph even at 70.
    Just love my HONDA Crosstourer dct, and my manual TDM900.

  • Offline BiKenG

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    Offline BiKenG

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    Re: Tyre size can it affect speedo reading
    Reply #6 on: May 29, 2020, 10.47 am
    May 29, 2020, 10.47 am
    Speedos in most vehicles are deliberately set to read fast, by how much depends on the manufacturer. It is not 'error' as they could be made accurate if desired.

    On the VFR1200 the speedo reads from the rear wheel rotation and any change in tyre circumference will affect the speedo reading, but in the normal range of suitable tyre sizes, not by any significant amount.

    If you want an accurate speedo, just fit a Speedo Healer. They can be configured to be completely accurate.
    You can't have too many bikes.

  • Offline Max2007

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    Offline Max2007

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    Re: Tyre size can it affect speedo reading
    Reply #7 on: May 29, 2020, 11.15 am
    May 29, 2020, 11.15 am
    I do not very care about this, all my bikes do the same and  i m above speedlimits anyway!!
    Only my old Mercedes W124, is on another side when you go 100kmh GPS reads 105kmh!!!

     



    arab-exile