"Resound" <
[email protected]> wrote in message
news:
[email protected]...
>
>
> Of course, if you just want the value you need, set it to 2179
> (~2207/1.013)
>
That would work......assuming that the km markers are exactly 5km apart.
From memory (and it has been a while since I had to set one), my speedo
manual states 2210mm for a 622-23 (ie. 700c) tyre and 2205mm for a 2.1 inch
wide mtb tyre (ie. 26"). I usually accept these values as being close
enough although I can remember a mate of mine some years ago spending a bit
more time in getting an accurate result....
The simple way to measure circumference is to draw a line on the ground and
line up the valve on your wheel with the line.....wheel your bike forwards
until the valve rotates around to the ground again....draw another
line....distance between lines is what you enter into the
speedo.....simple!! But this was not accurate enough for my mate.....he
insisted that he had to be on the bike as this would compress the tyres,
effectively reducing the circumference. He also had to buy a speedo that
used the rear wheel as it is less prone to wobble about and travel further
than you have actually gone. Finally, he wasn't happy with measuring one
rotation and so I got roped into helping him measure 10 rotations,
effectively reducing any measurement errors by a factor of 10. At the time
I can remember being tempted to ask him how much confidence he had in the
tape measure that we were using but I didn't want to spoil it all for him!!!
I can't remember the final figure that he entered but I do remember that
when we rode side by side we would have the same speedo measurement!!!
For a 1.3% error at say 30km/h, you are only going to be out by 0.39
km/h......do you need it to be more accurate than this??
Gags