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Author Topic: chain stay length, gear ratio chart...  (Read 10417 times)

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Offline Thepoolman

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chain stay length, gear ratio chart...
« on: March 17, 2016, 05:36:35 PM »
haven't been on here in ages... what happened to the chain stay length/ gear ratio chart...

or what would the  length of  30-9 - 31-9     33-9 33-10 be?

trying to get slammed on a 13.75 frame.   but also need that man gear ratio.     I used to always run 27-9  but i need a much harder ratio.   

 Thanks!


Offline Thepoolman

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Re: chain stay length, gear ratio chart...
« Reply #2 on: March 18, 2016, 08:22:02 PM »
I saw that... but the only thing that helps me off that is 30/9.     the old bg chart had 31 and 33.   

Offline Narcoleptic Insomniac

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Offline dersou ousala

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Re: chain stay length, gear ratio chart...
« Reply #4 on: March 19, 2016, 05:48:27 PM »
31/9 and 33/9 would be good for 13.75. The other would sit at 13.875 or 13.625.
but damn... 33/9 thats a manly gear ratio

Offline Thepoolman

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Re: chain stay length, gear ratio chart...
« Reply #5 on: March 19, 2016, 10:44:13 PM »
I'm running 33-10 now and its too easy.  Riding around the city is way way too much work with an easy ratio and I rarely pedal when at skateparks.   Looks like ill be staying with 33-10 or 31-9.   Thanks dudes.

Offline weedbix

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Re: chain stay length, gear ratio chart...
« Reply #6 on: March 19, 2016, 10:57:19 PM »
That chart is wrong. The BG chart was wrong too. This one is the most accurate:

http://eehouse.org/fixin/formfmu.php?maxRing=33&minRing=30&maxCog=9&minCog=9&stayLen=13.75&wheelDiam=19.15&isMetric=0&display=table&useHalfLink=1&stretch=0.00&axleAdjust=vert&sortKey=Stay_length

Be aware that the way some frames rear ends' are measured is inconsistent

Offline montymitch

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Re: chain stay length, gear ratio chart...
« Reply #7 on: March 20, 2016, 10:31:46 AM »
I think there are simply too many variables to have a 100% accurate chart. They only time I've needed one was to see if changing from a 28t to 25t would require a half link adjustment. Chain stretch, sprocket wear, chain line, and the current moon phase all figure in to the reality of making things work right.

Offline dude...

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Re: chain stay length, gear ratio chart...
« Reply #8 on: March 22, 2016, 12:34:00 AM »
yeah, once a new chain stretches it can make your back end at least half a cm longer, even more. so many threads on here about slamming the back end about 8 years ago lolz
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Offline weedbix

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Re: chain stay length, gear ratio chart...
« Reply #9 on: March 22, 2016, 04:09:21 AM »
True, there is variation. But it's variation from a value we CAN totally predict

Offline dude...

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Re: chain stay length, gear ratio chart...
« Reply #10 on: March 23, 2016, 07:12:07 PM »
totally true, people just sometimes forget that there will be a bit of variation over time as things bed in
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Offline Sasha

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Re: chain stay length, gear ratio chart...
« Reply #11 on: March 24, 2016, 11:44:20 AM »
I'd be surprised if most BMX companies didn't just weld on random length rear ends making this totally useless.

Bikeguide.org - Bike maintenance for BMX'ers

Re: chain stay length, gear ratio chart...
« Reply #11 on: March 24, 2016, 11:44:20 AM »

 

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