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This math nut's dream drivetrain :-)
#1
Heck, I'm probably more of a math nerd than a serious bicyclist, but whatever. I happened across, and downloaded, an Excel spreadsheet that allows one to enter one's tire size and calculates gear inches based on that size. I proceeded to highlight all my gear ratios by coloring the cells bright green, and then happened upon the idea of an "ideal" drivetrain while looking at other cells in the sheet.

I came up with this, and I'd like to hear what y'all think:

Chainwheels -- 44/34/24

10-speed cassette -- 11/13/14/16/18/21/24/27/30/34

For those familiar with gear inches, this gives a range of 20 (in the 24 front/34 rear combination) to 113 (in the 44/11 combination) for my bike, with 700x45 tires. Furthermore, most of the ratios are pretty close to being 12% different from the adjacent one, which avoids a lot of huge jumps from one gear to the next. (My current bike has a couple 25%+ jumps when using a reasonable shifting pattern.)

The following shift pattern in this "dream" drivetrain only skips one 12%-ish ratio jump on the way up: (front number/rear number)

1/1, shift only the rear up to 1/5
Double shift from 1/5 to 2/4
Shift only the rear from 2/4 to 2/8
Double shift from 2/8 to 3/7
3/7 up to 3/10

The only place there is a greater than 12% jump is the double shift from 1/5 to 2/4, where the ratio jumps about 25%. With a two-gear right-hand shift here, going from 1/5 into 2/3, the 12% jumps are preserved, albeit at the expense of having to execute a more complex shift.
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#2
Well, I'm no serious cyclist either, bit it seems to me that I only use 3 or 4 sprockets ("gears") out of the possible 12 available on my Schwinn Super Le Tour. I think many people are the same way. And the latest trend has been to throw all that stuff out and build a single-speed. Why? I have no idea. But like I said, I rarely use all the available sprockets.

Steve
Junkyard Tools rescued from the junkyard!
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#3
less is more
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#4
resurrecting an old post, interesting discussion here about number of gears.
http://www.jakesbikes.co.uk/content/348.php
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#5
I have 3 bikes,two with 21 gears and one with 27. I never miss the extra gears on my 21 speed bikes. And when the drivetrain wears out on my 21 gear "town" bike I'm thinking of changing it to a single speed to make it simpler and easier to maintain. Getting rid of the heavy steel deraileurs on this cheap and rather heavy bike, along with the extra chainrings, sprockets and cables will probably lighten it by two or three pounds as well.

I also quite like the idea of hub gears which have evenly spaced ratios and no duplicates, like Rohloff: http://www.rohloff.de/en/. If they were a bit lighter and a lot less expensive I'd be very tempted. Shimano, SRAM and Sturmey Archer also produce hub gears and their popularity on commuter/hybrid type bikes seems to be growing, so their may be some interesting products a bit further down the line.
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#6
(10-14-2010, 11:19 AM)trevgbb Wrote:  resurrecting an old post, interesting discussion here about number of gears.
http://www.jakesbikes.co.uk/content/348.php

Thanks, that is an XLNT article and I strongly agree with it. All you have to do is count the teeth on the freewheel/hub's sprockets to get the high and low gearing to see that most all bicycles are pretty much the same, except some have more gears (sprockets) in-between and choices than others. (roughly 12-14 for high and 28 to 32 for low) So why complicate something mechanical? That just means there is more to go wrong with it.

The high number of gears today is just a marketing gimmick to sell more NEW bikes. . . .kinda like that guy with the ceramic bearings that turned to dust. Smile

Message to bike manufacturers: If it works, don't fix it.

Steve
Junkyard Tools rescued from the junkyard!
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