gearing question
Hello, how would I work out the crossover between the gears on the larger chainring and the gears on the smaller one?
ie is 5th gear on the large chainring the same as 10th gear on the smaller one? is there some mathematical formula? Any help gratefully received. |
Click here Good luck.
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It's better to think of it as the small chainring is for climbing and headwinds while the large is for flat, tailwinds and desents.
You're never going to move through the gears in an exact progression. If you did then you would be constantly switching chainrings and moving up and down the cassette. |
Originally Posted by GlennR
(Post 21663387)
It's better to think of it as the small chainring is for climbing and headwinds while the large is for flat, tailwinds and desents.
You're never going to move through the gears in an exact progression. If you did then you would be constantly switching chainrings and moving up and down the cassette. |
Originally Posted by GlennR
(Post 21663387)
It's better to think of it as the small chainring is for climbing and headwinds while the large is for flat, tailwinds and desents.
You're never going to move through the gears in an exact progression. If you did then you would be constantly switching chainrings and moving up and down the cassette. |
There are going to be times when you feel like you are in between gears on the one chainring, you are either spinning too fast, too easy or too slow, too hard.. Time to shift to the other chainring. Generally, if shifting from the small ring to the big ring up shift 2 gears before going to the big. If going from the big ring to the small ring, downshift 2 gears before going to the small. That is what works for me. Sometimes I will have to shift another gear once I have changed from one ring to the other. On long rides, it makes a difference in expended effort when in the proper gear.
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Originally Posted by benjamin163
(Post 21663366)
Hello, how would I work out the crossover between the gears on the larger chainring and the gears on the smaller one?
ie is 5th gear on the large chainring the same as 10th gear on the smaller one? is there some mathematical formula? Any help gratefully received. That said, the tool linked to in post #2 is very illustrative and easy to use. |
Ratio math quiz: count teeth .. it's a number . use those numbers, calculate, to learn the ratio ...
like 44:11 is 4:1 50:11 ,,,, is 1: 4.545454545454... |
Or if you have a triple -------------small chain ring for up hills-----------middle ring for most riding---------------large chain ring for down hills or with the wind.
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Originally Posted by rydabent
(Post 21663766)
Or if you have a triple -------------small chain ring for up hills-----------middle ring for most riding---------------large chain ring for down hills or with the wind.
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There should be about 2 gears in the rear difference between chainrings. You shouldn't be trying to use them that way though. As mentioned above choose your chainring based on the range you need. Then fine tune your shin with the rear gears.
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Originally Posted by benjamin163
(Post 21663366)
Hello, how would I work out the crossover between the gears on the larger chainring and the gears on the smaller one?
ie is 5th gear on the large chainring the same as 10th gear on the smaller one? is there some mathematical formula? Any help gratefully received. https://www.sheldonbrown.com/gear-theory.html I believe that piece was written around the turn of the century, but most of the information still applies to bikes made in the 2 decades since. Good luck! |
OP, calculating your gears is the way to "get" what you need to do to find shift patterns that match your riding style. (It might even encourage you to change the gears top better fit. See my gear choices above. I've never seen my choices on a stock bike but I love 'em. Before I aged, I rode 53-42-28 X a variety of freewheels and cassettes, all having 13,14,15,17,19 and adding more cogs as the numbers grew. I live around real hills, some quite steep and I love to climb. Having a bike that doesn't allow me to go up them doesn't work for me. (I've been known to pull out middle cogs and add 25 and 28 tooth cogs.) Ben |
Originally Posted by 79pmooney
(Post 21663876)
I couldn't get that calculator to run custom chainrings and cogs. (50-38-24 X 12,14-19, 21,23 9-speed) I hit :custom" but the chart just went blank. I saw no way to enter my sprockets.
OP, calculating your gears is the way to "get" what you need to do to find shift patterns that match your riding style. (It might even encourage you to change the gears top better fit. See my gear choices above. I've never seen my choices on a stock bike but I love 'em. Before I aged, I rode 53-42-28 X a variety of freewheels and cassettes, all having 13,14,15,17,19 and adding more cogs as the numbers grew. I live around real hills, some quite steep and I love to climb. Having a bike that doesn't allow me to go up them doesn't work for me. (I've been known to pull out middle cogs and add 25 and 28 tooth cogs.) Ben |
Originally Posted by fietsbob
(Post 21663741)
Ratio math quiz: count teeth .. it's a number . use those numbers, calculate, to learn the ratio ...
like 44:11 is 4:1 50:11 ,,,, is 1: 4.545454545454... OP, "gear inches" is simply the wheel an early bike rider on the high-wheeler of the 1880s was riding. (Also your kid's tricycle.) Both travel one wheel circumference with one complete pedal revolution. The bigger the wheel the farther you went. So riders talked about the "wheel" they were riding. (And racing started right away because that is whet we male humans do.) Everybody "got " that bigger wheels were faster. (And with the need to straddle that big wheel in those high-wheelers, small people needn't apply for jobs as pro bike racers.) Then chains came along. Suddenly anybody could ride any "wheel" they wanted. Since talking wheel diameter was accepted, people just kept doing exactly that, except now that "diameter" was the diameter of the equivalent high-wheel. Calculating it is simple measuring the outside diameter of the wheel you are riding and multiplying by the gear ratio used. (700c and 27" wheels with normal road tires come out close enough to 27".) Chainring Teeth / Cassette Teeth X Wheel diameter (27" for most of us) = Gear Inches. Say 39 teeth in front, 18 teeth in back: 39 /18 X 27 = 58.5" (or a higher-wheeler of just under 5 feet). Gears over 100" are considered "high". Gears in the 60s, 70s and 80s "normal" for flat ground. Gears down to the 20s for climbing. Below that for fully loaded touring climbing. (If you ever deviate from the common road wheels to say 29ers or folding bikes you will see where gear inches is much more useful than "ratios". You and your much smaller wife or kid can ride different wheeled bikes; both in 72" gears and pedal the same speed.) Ben |
Recently, right here on BF I learned you can print a gear chart and tape it to your stem or bars! :thumb:
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Originally Posted by caloso
(Post 21663906)
Click and drag the chainring on the left over to the line to add a chainring. You can move them wherever you want on the range. Same with the rear cogs in the line below.
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Originally Posted by shelbyfv
(Post 21663970)
Recently, right here on BF I learned you can print a gear chart and tape it to your stem or bars! :thumb:
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chain wheel : cog .. ratio x wheel diameter in inches, is 'gear inches'..
gear ratio x wheel circumference in meters is 'development' how far you go down the road, with 1 petal rotation.. |
Originally Posted by BoraxKid
(Post 21663829)
Nope, wrong again. My triple is used thusly: big ring for most riding, middle ring for most climbing, small ring for extreme and/or loaded climbing.
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Sheldon Brown's gear calculator:
https://sheldonbrown.com/gear-calc.html |
I like the Mike Sherman calculator the best
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Originally Posted by GlennR
(Post 21663387)
It's better to think of it as the small chainring is for climbing and headwinds while the large is for flat, tailwinds and desents.
You're never going to move through the gears in an exact progression. If you did then you would be constantly switching chainrings and moving up and down the cassette. |
I spent the time to make an Excel spreadsheet that calculates the ratios of all the gears on all my bikes, which was fun, but on the road it boils down to this:
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Originally Posted by BoraxKid
(Post 21663829)
Nope, wrong again. My triple is used thusly: big ring for most riding, middle ring for most climbing, small ring for extreme and/or loaded climbing.
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