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Join Date: Feb 2012
Location: Rochester, NY
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Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
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Yes, I think you would find that some of your 24 "speeds" are dups (or very close) of each other. And that one nor the other of a dup set will have the chain in a less angled run. Or one will be easier to shift into from the ratio ine is currently in.
The absolute best, no math and no counting dirty teeth, way to see what gear ratios really do is to do a roll out for each cog/ring combo. You'll need a long enough tape measure, a couple of pencils/pens/nails and your bike (oh, and a paper and pen to record your findings). Shift the bike into the small front ring and the largest rear cog (your lowest uphill gear). Place the rear wheel so that the valve is at the ground and place one of the markers on the ground right at the valve. Place the cranks so one is exactly at the bottom of the stroke. With your hands roll the bike forward while also turning the crank around one full rotation. Stop when that same crank arm is again at the bottom and mark the rear wheels contact point with the ground. You have found out how far forward the bike goes in this gear for one rotation of the crank. Measure and record. Repeat for each cog/ring combo. You will end up with 24 measurements of how far each gear allows the bike to travel. This is an analog version of a ratio chart. You will see that some gears are nearly the same travel forward as another gear is. These are your duplicates.
In the USA we refer to a gear ratio in what's called inches of development. This is what the imaginary rear wheel diameter would need to be to result in the bike's travel forward IF the cranks were directly connected to that wheel (much like a kid's tricycle or a unicycle has). You will see that in your fastest downhill gears the virtual wheel diameter is many times your leg length and would be impossible to straddle and pedal if you didn't have cogs and rings. In Europe where the metric system rules (bad pun) they use the distance the bike travels forward as the gear reference (once again showing how much more sense the Metric system makes). Andy
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AndrewRStewart