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Old 06-13-19, 12:20 PM
  #1  
monstorr
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Upgrade

Hi Everyone, just had a quick question that would probably be answered very easily.

I would like to upgrade the bike to have a 2x instead of the current 3x on there. I aim to ride this bike for cyclocross so im guessing a 46/36t? The bike has 8 speed STI shifters and a 12-25t cassette in the back.

Are there any supporting mods I should do before/after changing the crank?

Thanks in advance for any tips!

-Richard
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Old 06-13-19, 12:46 PM
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caloso
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I don't think there's much to do other than make sure your lower FD limit is set so you don't accidentally shift your chain off. You'll have useless click, but other than a totally slack cable, I don't think there's any issue.
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Old 06-13-19, 01:44 PM
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Depending on what type of STI you have, you can decide which shift positions to use, small to middle or middle to large. Then use the FD limit screw to lock-out the unused position.

The differences between the position (S->M) vs. (M->L) are:
*Trim position availability, if you have and/or want them.
*Cable pull/tension, with Shimano STI the SM shift pull a little more cable than the ML shift. This is designed-in to take up any extra slack. This may help shifting speed and allow you to use a lower tension in the small ring.
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Old 06-13-19, 04:26 PM
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dsbrantjr
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A possible downside to locking out the M>L shift is that if you forget and force the shift you may jam the ratchet such that you cannot shift back down; you could even damage the mechanism.

Personally I would not consider going from 3x to 2x an upgrade but others might; I would miss those low range gears, and to get the same range out of 2 rings would necessarily spread out the remaining gears so the gaps would be bigger.
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Old 06-13-19, 05:54 PM
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Originally Posted by dsbrantjr View Post
A possible downside to locking out the M>L shift is that if you forget and force the shift you may jam the ratchet such that you cannot shift back down; you could even damage the mechanism.

Personally I would not consider going from 3x to 2x an upgrade but others might; I would miss those low range gears, and to get the same range out of 2 rings would necessarily spread out the remaining gears so the gaps would be bigger.
I was very excited to build up my 8 speed bike with a triple (it's Campy Chorus). Didn't take me long to decide I hated it and switch to a compact crankset.

YOu might need to consider chain length depending on your new gear set.
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Old 06-13-19, 06:09 PM
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caloso
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Originally Posted by dsbrantjr View Post
A possible downside to locking out the M>L shift is that if you forget and force the shift you may jam the ratchet such that you cannot shift back down; you could even damage the mechanism.

Personally I would not consider going from 3x to 2x an upgrade but others might; I would miss those low range gears, and to get the same range out of 2 rings would necessarily spread out the remaining gears so the gaps would be bigger.
He said he's using the bike for cyclocross so on anything you'd need an ultra-low gear, you're probably better off dismounting and running up anyway. There aren't a lot of mile-long grinders on CX courses, just short steep pitches where you want to carry speed and muscle over it, if possible. Dismount and shoulder if not.
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