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Thread: Bc800

  1. #1


    I'm hoping someone is alive currently to help me solve the final step in installing my BC800.

    Trying to figure out the magic number that gets entered into the computer to give you accurate readings.

    1.) The instructions say the formula is mm x 3.14 x 10. Now this has to be incorrect. Say my wheel is 53cm x 10 is 530mm x 3.14 is 1664.2 x 10 is 16642. Now the chart is only allowing for numbers in the thousandths not the tens of thousandths. I'm assuming the formula SHOULD be cm x 3.14 x 10. So I believe my magic number is 1664.2

    2) Now looking at the table, the closest number to 1664.2 is 1590. Would I use that, or simply enter 1664?

    Any help would be greatly appreciated, I leave tomorrow at 11am for a weekend up in Ashcroft. Feel free to call me as well, 861-1829.



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  3. #2

    Does "tomorrow" mean Friday or Saturday...?

    In any case, you are correct the formula is in error.

    The "magic number" represents the wheel circumference in mm. In other words, how far the bike travels in one wheel rotation. For your example it is 1664 mm so enter that figure (the chart is only for people who don't care about their speedo accuracy...).

    By the way, any errors in this number creates the same errors in your speedo reading so get this number as correct as possible!!! Measuring the wheel diameter and multiplying by PI (3.14) is fine on a bicycle but a poor method on a motorbike.

    It's best to measure the distance the bike moves in one revolution directly to account for static tire shape/deflection due to the bikes weight. Dynamic errors are insignificant and can be ignored.


  4. #3
    Moderator Array TeeTee's Avatar
    Join Date
    Feb 2002
    Out to pasture in the 'Wack
    04 Kawi Z1000,
    That's right. Bicycle tires don't squish down as far as a motorcycle tire will. Use some tire chalk to mark the tire and the start point and roll it forward by one circle. Use a carpenters square to line up the axle center to the chalk mark to be sure that the wheel moves exactly one full turn.
    A backyard mechanic without a service manual is just like a hooker without a lamp pole.... they are both in the dark.

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