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Gearing question-road bikes

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Gearing question-road bikes

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Old 03-16-04, 09:33 PM
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RacerX
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Gearing question-road bikes

How do you figure out comparable gearing?
For example;
does a 53x12 = 52x11?
39x23 = 42x26?

I guess I'm asking if 1 tooth off the chainrings is the same as 1 tooth off the rear cogs.

I'm a dummy with this stuff so thanks in advance
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Old 03-16-04, 09:39 PM
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MacMan
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This doesn't exactly answer your question ... but it's quite cool anyway!

http://www.arachnoid.com/bike/
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Old 03-16-04, 09:44 PM
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Originally Posted by RacerX
I guess I'm asking if 1 tooth off the chainrings is the same as 1 tooth off the rear cogs.
No....
It's best to just convert your gearing combos into gear inches and work from there.......
Gear inches = #chainring divided by #cog and multiply that number by 27.

George
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Old 03-16-04, 10:18 PM
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SteveE
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Why dontcha' go here and plug in a few numbers?

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Old 03-16-04, 10:19 PM
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ok thanks. That link is pretty cool too
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Old 03-17-04, 09:37 AM
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Here is the one I use -

www.panix.com/~jbarrm/cycal/cycal.30f.htm

It gives you all you will need (except a degree in physics to make sense of it).

Now that you have all that information, it has been my experience that you will find what gears work best for you by good old trial and error! What ultimately works best for you is what you should use. Some pepole feel fine jumping up two or four teeth on the cassette while others do best with closer gear changes. Ultimately this will also give you some idea about what cassette will work best for you and your style of riding.

So much for my pontificating!!

Bill
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Old 03-17-04, 09:49 AM
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It seems on the surface that it would work out to be the same but 52/11 = 4.72 and 53/12 = 4.42. The number closer to 1 is easier to push. If you think about say a triple set up with a 30 chain ring and a 30 rear cog that ratio is 30/30=1 and is very easy to push. raising the tooth count up front to say a 32 now 32/30 is some number greater than 1 and harder to push...
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Old 03-17-04, 11:39 AM
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It's a matter of ratios. To get the "equivalent" chainring for a cog change, multiply the gear ratio by the new cog size.

Example: 53/12*11 = 48.6

So the closest gear to a 53/12 using an 11T cog is 49/11.

To get the "equivalent" cog for a chainring change, divide the new chainring size by the gear ratio.

Example: 42/(39/23) = 24.8

So the closest gear to a 39/23 usnig a 42T chainring is 42/25
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Old 03-17-04, 11:41 AM
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Originally Posted by jfmckenna
It seems on the surface that it would work out to be the same but 52/11 = 4.72 and 53/12 = 4.42.
....and factor in the actual wheel diameter, then you'll get 128 and 119 gear inches, respectively......which is a noticable difference.

George
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Old 03-17-04, 12:22 PM
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Originally Posted by wlevey
Here is the one I use -

www.panix.com/~jbarrm/cycal/cycal.30f.htm



Bill
Link doesn't work
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Old 03-17-04, 12:27 PM
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Add an l to the URL: http://www.panix.com/~jbarrm/cycal/cycal.30f.html
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Old 03-17-04, 12:30 PM
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Originally Posted by The Fixer
....and factor in the actual wheel diameter, then you'll get 128 and 119 gear inches, respectively......which is a noticable difference.

George
So that means for every rotation of the wheel you go 9 inches farther with the 52x11 compared to the 53x12? Is that right?
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Old 03-17-04, 12:43 PM
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I did this a few weeks ago and found it useful. It was relatively easy with Excel.

link here

-mark
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Old 03-17-04, 12:59 PM
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[QUOTE=RacerX]So that means for every rotation of the wheel you go 9 inches farther with the 52x11 compared to the 53x12? Is that right?[/QUOTE

.....should read... 'for every rotation of the crank'.....
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