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Trail Junky
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1x12 shifting problem
06/07/20 at 9:50am
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Hey,

I have an SRAM Eagle SX 1x12 setup new late August 2019, and the derailleur won't shift from larger to smaller cogs when tension is on the chain.  Well, it might eventually shift and then jump more than cog.  It does move reliably up and down the cassette with the chain removed.  Although the derailleur is also be having some trouble shifting from smaller to larger cogs, this might be due to the chain as some links seem to be not wanting to move freely as they rotate around the cassette.  The high and low limits seem to be set correctly, and the chain is not worn enough for a gauge to fit.  I see no obviously bent teeth in the cassette.  Is there an wisdom to be shared?

Thanks,
-Clay
  

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Trail Junky
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Re: 1x12 shifting problem
Reply #1 - 06/07/20 at 10:16am
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I should add that I didn't notice a problem with shifting Uwharrie during my last ride on Sunday 5/31.  I washed the bike the next morning and oiled the chain after everything had dried.  I then noticed the shifting problem.
  

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Tom F
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Re: 1x12 shifting problem
Reply #2 - 06/07/20 at 12:39pm
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Your chain has issues. The first step is to either replace the chain or free those stiff links.
Leave the limit screws alone!
Clean the cassette, derailleur with a stiff brush. Lightly lube the pivot points. 
Check for a bent hanger.

Failing that take it to a shop and either have it repaired or buy a new bike. Smiley
  

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Re: 1x12 shifting problem
Reply #3 - 06/07/20 at 1:57pm
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Thanks Tom for the info.  I found this when I returned to post an update.  I was able to resolve the problem since posting my request for help.  The whole bike is new as of August 2019.  It proved to be the chain being too short.  I had a link break right in front of or behind the quick link a several weeks back at Sherman.  I removed this trail-side and the next one since it seemed to be problematic at the time.  I had not yet replaced the chain since everything seemed to be working fine in subsequent rides.  With the new chain set to match the original length and installed, shifting was again behaving properly.
  

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Tom F
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Re: 1x12 shifting problem
Reply #4 - 06/07/20 at 10:42pm
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Trail Junky wrote on 06/07/20 at 1:57pm:
Thanks Tom for the info.  I found this when I returned to post an update.  I was able to resolve the problem since posting my request for help.  The whole bike is new as of August 2019.  It proved to be the chain being too short.  I had a link break right in front of or behind the quick link a several weeks back at Sherman.  I removed this trail-side and the next one since it seemed to be problematic at the time.  I had not yet replaced the chain since everything seemed to be working fine in subsequent rides.  With the new chain set to match the original length and installed, shifting was again behaving properly.



Yup a short chain would for sure cause problems! 
Glad you won't need a new bike, unless you want one of course. Smiley
  

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Re: 1x12 shifting problem
Reply #5 - 07/02/20 at 1:50am
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Trail Junky wrote on 06/07/20 at 1:57pm:
Thanks Tom for the info.  I found this when I returned to post an update.  I was able to resolve the problem since posting my request for help.  The whole bike is new as of August 2019.  It proved to be the chain being too short.  I had a link break right in front of or behind the quick link a several weeks back at Sherman.  I removed this trail-side and the next one since it seemed to be problematic at the time.  I had not yet replaced the chain since everything seemed to be working fine in subsequent rides.  With the new chain set to match the original length and installed, shifting was again behaving properly.

Whenever you shorten or lengthen the chain on SRAM 1x11 or 1x12 you must readjust the B tension screw.  The guide pulley on the derailleur is offset from the pivot and chain length changes affect the distance from the guide pulley to the cassette.  Too short a chain made too much distance between the two creating a lag in your shifting.
  

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