As a former amateur racing cyclist, I can give you the definitive answer.
It's the effective diameter of the wheel for a given gear. My bicycle was a
10-speed. The two chain wheels had 49 and 46 sprockets. The "five-block" on
the rear wheel had 14, 16, 18, 20 and 22 sprockets. The wheels were 27"
(this was Britain in 1956) with sprint rims and tubular tires ("sew-ups" is
the American term). Top gear was 94.5 inches (27*(49/14)). Bottom gear was
56 inches (27*(46/22)).
Obviously, these days, I would be talking about 69 cm wheels and a 144 cm to
240 cm gear range..
Bill Potts, CMS
Roseville, CA
http://metric1.org [SI Navigator]
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
>Behalf Of Michael Payne
>Sent: Wednesday, March 05, 2003 09:54
>To: U.S. Metric Association
>Subject: [USMA:25032] Gear Inches
>
>
>I recently received a copy of the Washington Consumer Checkbook
>(www.checkbook.ord), a Consumer Reports style magazine for the Greater
>Washington DC area. It's published by the Center for the Study of Services.
>On an article on bikes, it states the gear ratios of a bicycle are
>described in terms of gear-inches. I've never heard of this before,
>fortunately most everything on bicycles is in metric, including all the
>wrenches, the mass of different parts are expressed in grams in most
>catalogs.
>I'd like to find out what the correct term here is so i can write to them.
>I'm sure its supposed to be a ratio of how many teeth per cog.
>
>Thanks
>
>
>--- Michael Payne
>--- [EMAIL PROTECTED]
>--- EarthLink: The #1 provider of the Real Internet.
>
