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Going from a 54/42 to a 50/34, help?

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Going from a 54/42 to a 50/34, help?

Old 06-23-11, 12:26 PM
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CJ C
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Going from a 54/42 to a 50/34, help?

hello all you wonderfully knowledgeable people that are so kind.

ok the kiss up is done now to the meat. Well i have a late 80's 12speed road bike which i assume has a 54/42 crankset i have a friend at work that will giving me a FSA carbon 50/34 crankset and Bottom bracket that is used and scratched up.

first will it even fit?
second how odd will the gearing be?
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Old 06-23-11, 12:39 PM
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Originally Posted by CJ C View Post
hello all you wonderfully knowledgeable people that are so kind.

ok the kiss up is done now to the meat. Well i have a late 80's 12speed road bike which i assume has a 54/42 crankset i have a friend at work that will giving me a FSA carbon 50/34 crankset and Bottom bracket that is used and scratched up.

first will it even fit?
second how odd will the gearing be?
The answer is - it depends. You will probably be okay with threading of the bottom bracket because the majority of bikes use English threading but that isn't guaranteed. The 50/34 is going to have significantly lower gearing with a 6 speed. I'm assuming a freewheel with a 13 or 14 tooth gear on it. If it's a 14 tooth gear, you'll drop from a 104 gear inch high to a 96 gear inch high.
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Old 06-23-11, 01:14 PM
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Originally Posted by cyccommute View Post
The answer is - it depends. You will probably be okay with threading of the bottom bracket because the majority of bikes use English threading but that isn't guaranteed. The 50/34 is going to have significantly lower gearing with a 6 speed. I'm assuming a freewheel with a 13 or 14 tooth gear on it. If it's a 14 tooth gear, you'll drop from a 104 gear inch high to a 96 gear inch high.
thanks cyccommute, i think the gearing might be to low for me as i dont even use the 4 lowest gears ever and after a stop light i jump to the big front ring after about a block. (could be i am pedaling and shifting wrong as i am clue less on that)

I will just tell him thanks but no thanks and to craigslist it and get some money for it.
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Old 06-23-11, 02:51 PM
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Originally Posted by CJ C View Post
hello all you wonderfully knowledgeable people that are so kind.

ok the kiss up is done now to the meat. Well i have a late 80's 12speed road bike which i assume has a 54/42 crankset
Why assume. If you don't know count the teeth. The odds are good that your crankset is a 52/42 or 52/39. Unless you are a professional road racer it's a good bet that smaller rings and a higher cadence would help you. And a lot depends on what kind of terrain you are riding and the number of teeth on the freewheel cog set.
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Old 06-23-11, 02:53 PM
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Taking the top end down from 54T to 50T is roughly the same as a one tooth change on the cassette/freewheel. Not huge but only you can answer that.
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Old 06-23-11, 07:30 PM
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Originally Posted by CJ C View Post
Well i have a late 80's 12speed road bike which i assume has a 54/42 crankset i have a friend at work that will giving me a FSA carbon 50/34 crankset and Bottom bracket that is used and scratched up.

first will it even fit?
second how odd will the gearing be?
Wouldn't know til I see the bike and the crank. And the bottom bracket.
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Old 06-24-11, 07:31 AM
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Originally Posted by Al1943 View Post
Why assume. If you don't know count the teeth. The odds are good that your crankset is a 52/42 or 52/39. Unless you are a professional road racer it's a good bet that smaller rings and a higher cadence would help you. And a lot depends on what kind of terrain you are riding and the number of teeth on the freewheel cog set.
counted them last night it is a 52/42. I ride pancake flat terrain but get some tough winds and wind gusts. still havent taught myself to spin at a high cadence i keep falling back to the habit of mashing away at the pedals.
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Old 06-24-11, 07:34 AM
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Originally Posted by CACycling View Post
Taking the top end down from 54T to 50T is roughly the same as a one tooth change on the cassette/freewheel. Not huge but only you can answer that.

im am just worried that with the lower gears i wont ever use them and then not having enough top speed. well i guess anyways i shouldnt really go that fast in an old road bike i fixed myself
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Old 06-24-11, 07:45 AM
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Originally Posted by CJ C View Post
im am just worried that with the lower gears i wont ever use them and then not having enough top speed. well i guess anyways i shouldnt really go that fast in an old road bike i fixed myself
Go run the numbers. This gear calculator lets you see the gears in a nice format. Very intuitive.
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Old 06-24-11, 10:02 AM
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Originally Posted by cyccommute View Post
Go run the numbers. This gear calculator lets you see the gears in a nice format. Very intuitive.
Oh nice! That site is way helpful, thanks for the link!
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Old 06-24-11, 10:41 AM
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Originally Posted by cyccommute View Post
Go run the numbers. This gear calculator lets you see the gears in a nice format. Very intuitive.

that is the coolest website, thank you for that!
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