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Discussion Starter · #1 ·
At the risk of sounding like an idiot...

I have an '08 Air 9 that I want to run SS on. So I did my research and found that everyone is running the 32/20 "magic gear". I have a truvativ 32t ring on the front and 20t from an old cassette on the back. I have a brand new SRAM 8 speed chain with 47 links plus the quick link (47 outer plates). There is definitely too much slack with this combination.

However, if I put on my old 9 speed chain with 46 outer plates plus the quick link that is stretched, the chain is way too tight and I can't even get the wheel in the drops.

Did niner change the geometry from 08 to 09? Is it possible that my chain stays are longer or shorter than the current models?

Any help is greatly appreciated!
 

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This site:
http://eehouse.org/fixin/fixmeup.php

has pretty good instructions on figuring out what ratios you can run based on the chainstay length. You might want to measure them and then use their tool.

Or you can just get a tensioner and run a slightly longer chain. Not as pretty looking, but works.

EDIT: You can also look into an eccentric hub. I think ENO makes one. You might run into problems if you use a rear disk brake though.
 

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Angry bunny
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4,948 Posts
wrxg33k said:
The air9 stays are 44cm inches right? According to that calculator, with 44cm stays, 32/20 isn't a magic gear. Am I reading it wrong?
Please re-read my post that I linked.
The calculator that I used suggests that 32/21 is the magic gear for an Air9.
 

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Nompton, OK
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141 Posts
I ran into the same problem, I kept dropping the chain no matter which kind I was running. So I just decided to run a cheap tensioner from pricepoint that works flawlessly, and is fairly silent... It was incredibly frustrating when the magic ratio didnt work for me at first, but I got over it when I put on the tensioner and was able to hammer the AIR to my delight!
 

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Go Fast, Take Chances.
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I also run a tensioner(Surly Singulator in push up mode) on my Air 9 and have no issues what so ever. I don't really buy into the magic gear deal either, and here's why, chains stretch. If your riding a SS you are going to be mashing and putting some serious torque down and that's going to stretch your chain out, therefore, making your magic gear not so magic. Just my 2 pennies.
 
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