Back in spring 2002 there was some discussion about how to mount a computer
and route the wire without insulting the correct look of your classic. I
have a substitute for the bike computer that requires a watch with second
hand and functioning gray matter.
You need a spot on the rim or the hub that allows you to count revolutions.
For most road bikes, count wheel revs for 10 seconds and divide by two, or 15
seconds and divide by three. This gives you instant speed in MPH. Of course
its approximate. On one of my bikes it is accurate at 30 seconds/33 but
thats a long time to concentrate on counting revs esp on a busy road.
Distance can be approximated by multiple readings during flats, climbs, and
descents and applying a weighted average. But its easier to consult a map,
or use total time vs a known road distance for that. Just an idea to eschew
the computer.
The math is: precise diameter of the wheel (outside of tire) x Pi = distance
traveled in one revolution. Divide 1056 inches by your factor= number of
revs per minute for ONE MPH. In my example a 27" wheel is about 12 revs per
minute for 1 mph, thus 3 revs in 15 secs for 1 MPH. Metric calculations
parallel this.
Keith Bolog
Kenosha WI