chain stay length, gear ratio chart...

[Thepoolman]

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!

[montymitch]

http://www.vitalbmx.com/forums/General-BMX-Talk,2/Gear-Ratios-and-chain-stay-length,1282702

[Thepoolman]

I saw that... but the only thing that helps me off that is 30/9.     the old bg chart had 31 and 33.   

[Narcoleptic Insomniac]

http://eehouse.org/fixin/formfmu.php

[dersou ousala]

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

[Thepoolman]

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.

[weedbix]

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

[montymitch]

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.

[dude...]

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

[weedbix]

True, there is variation. But it's variation from a value we CAN totally predict

[dude...]

totally true, people just sometimes forget that there will be a bit of variation over time as things bed in

[Sasha]

I'd be surprised if most BMX companies didn't just weld on random length rear ends making this totally useless.