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From: fish@ihu1g.UUCP (Bob Fishell)
Newsgroups: net.bicycle
Subject: Re: Gear Ratios
Message-ID: <353@ihu1g.UUCP>
Date: Wed, 16-May-84 12:06:00 EDT
Article-I.D.: ihu1g.353
Posted: Wed May 16 12:06:00 1984
Date-Received: Thu, 17-May-84 03:12:34 EDT
References: <1474@sdccs6.UUCP>
Organization: AT&T Bell Labs, Naperville, IL
Lines: 16

(oo)
The references to "33-inch gears," etc. goes back to the old velocipedes
of bygone days.  A 33-inch gear is the equivalent of having the crank
connected directly to a wheel of 33 inches in diameter.  The bigger the
gear, the bigger the virtual wheel, and the faster you go per rpm.

Gear ratios are easily computed.  Just count the teeth on your chain
wheels and the freewheel.  If you have a 27" wheel diameter, the
virtual wheel size is 27 * #teeth in chain wheel / #teeth in freewheel.
For example, a 52-tooth chain wheel coupled with a 14-tooth freewheel
gear on a 27" bike gives a 27*52/14=100.28" virtual wheel.  This is
commonly called a "100-inch gear."
-- 

                               Bob Fishell
                               ihnp4!ihu1g!fish