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Originally Posted by lottos one thing that is interesting with these cycle odometers etc. is how they say to get the circumference of the wheel for inputting into the unit, yet when it comes to placing the censor on the wheel, it's no where near the circumference of the wheel - it's placed on the spokes which has a much smaller circumference than the outside of the wheel!  |
The sensor counts the revolutions and adds the wheel circumference to the distance each revolution.
The technique I use to determine the circumfirence of the tyre is:-
Pump tyres to normal riding pressure
with the rider on the bike
(I use a straight length of footpath)
mark start position with tyre valve stem at bottom of wheel
roll the bike in as straight line as possible for 10 wheel revolutions with the bike taking the weight of the rider.
mark the end position after 10 revolutions.
measure the distance between start and end positions in cm.
Enter the distance for 10 revolutions, for example 2050cm, as 2050mm as wheel circumference in mm.
A 25 to 30 metre tape is required.
if sensor is on rear wheel, rear wheel must be measured, for 10 revolutions of rear wheel.
Other number of wheel revolutions can be used(2, 4, 5, 8 etc), but distance
measured must be divided by the number of wheel revolutions.
10 is the easiest if you have the longer tape measure.
Mike