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Old 07-17-19, 03:58 PM
  #21  
HTupolev
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Originally Posted by Andrew R Stewart View Post
Detach the rear shift cable from the der and secure it with masking tape to the stays. Take a short piece of inner cable with a head on one end. Thread it through your der's casing stop/adjuster so the cable head is nestled inside the stop. With your hands shift the der into a central cog and while holding it there secure the cable to the anchor bolt. You can use the cable adjuster to trap the der directly under the cog, effectively creating a single speed. Now go out and ride in the way that would have caused the ghost shifting. You won't get any because the cable is no longer tugging on the shift lever. Andy
That doesn't sound like a very complete test, since the cable on the derailleur is no longer subject to flex between stops on the frame.

To test whether frame flex can cause ghost shifts by tugging on the cable (without budging the shifter), it seems like you'd need to use a long shift cable and anchor it at the location where downtube shifters or the downtube cable stops go. Then, if it does cause ghost shifts, you could also fiddle with the adjuster at the derailleur to test how prone the bike is to ghost shifts when the derailleur is at various degrees of off-centerness below the cog.
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