D
Dex
Guest
Accurate calibration of cycle computer
I measure the distance convered by several revolutions of the wheel
that I am calibrating. Make a scratch mark on the surface with the
valve stem at the bottom of the wheel. Make several revolutions of
the wheel and make another scratch mark with the stem at the bottom
again. I usually use 10 wheel revolutions. Measure this distance and
record it. If the distance was measured in feet, you usually have to
convert it to centimeters to use it in setting your wheel
circumferance. First, find your wheel circumferance by dividing the
distance by the number of wheel revolutions. Then multiply this
answer 30.48 -- this will be the number you use to set the wheel
size. Some cyclocomputers require different inputs for KPH or MPH. -
If you need to use a conversion factor to change from KPM to MPH,
simply divide the kilometer wheel size number by 1.61 - this should
give you speed and distance in miles instead of kilometers.
The tables included with bicycle electronic speedometers work pretty
well, but I like to calibrate them accurately, so I inflate my tires
to working pressure and sit on the bike while doing the wheel
measurements so that they will be more typical of actual operation.
I measure the distance convered by several revolutions of the wheel
that I am calibrating. Make a scratch mark on the surface with the
valve stem at the bottom of the wheel. Make several revolutions of
the wheel and make another scratch mark with the stem at the bottom
again. I usually use 10 wheel revolutions. Measure this distance and
record it. If the distance was measured in feet, you usually have to
convert it to centimeters to use it in setting your wheel
circumferance. First, find your wheel circumferance by dividing the
distance by the number of wheel revolutions. Then multiply this
answer 30.48 -- this will be the number you use to set the wheel
size. Some cyclocomputers require different inputs for KPH or MPH. -
If you need to use a conversion factor to change from KPM to MPH,
simply divide the kilometer wheel size number by 1.61 - this should
give you speed and distance in miles instead of kilometers.
The tables included with bicycle electronic speedometers work pretty
well, but I like to calibrate them accurately, so I inflate my tires
to working pressure and sit on the bike while doing the wheel
measurements so that they will be more typical of actual operation.