On Mon, 05 Jul 2004 12:56:36 GMT, "Mike"
<
[email protected]> wrote:
>
>On Sun, 04 Jul 2004 09:44:20 -0700, smokey wrote:
>
>>
>> My favorite has been my Planet Bike 8.0. Just the
>> necessary functions, and easy to set up and re-set. You
>> can get them at Performancebike.com.
http://www.performa-
>> ncebike.com/shop/Profile.cfm?SKU=12090
>
>How small a wheel diameter will it calibrate to? Will it
>calibrate for a 20" (409) wheel - and to what accuracy?
>I've seen posts on this and other NGs recently mentioning
>calibrations in the range of 100-200, to me that's not
>accurate enough - does is have 4 digits of calibraton?
>
>mike
Dear Mike,
Here are some reviews of the Planet Bike 8.0:
http://www.roadbikereview.com/Computers/Planet%20Bike,Plane-
t,Bike,Protege,8.0,Cyclocomputer/PRD_132758_1624crx.aspx
Most cyclocomputers allow entering a wheel circumference in
millimeters, either from a printed table of average sizes or
else from your own measurements.
For a ridiculously small 1% inaccuracy, you'd have to be
10mm off on a 1000mm tire, or 20mm off on a 2000mm tire, so
this is overkill anyway.
Most tables list a 700c tire at 2124mm, while a 20" is
listed at 1596mm. Technically, the smaller tire will be less
accurate because it has roughly the same measuring error
(plus or minus about an eighth of an inch) as the larger
tire, repeated more times in the same distance.
However, the 20" tire does have the inestimable advantage
that it may be just small enough for someone to build an
odometer that reads in thousandths of a mile (5.23 feet per
spin) instead of the lamentably coarse hundredths of a mile
of larger tires.
Carl Fogel