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Old 07-16-19, 08:09 AM
Andrew R Stewart 
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Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder

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The route cause of frame flex induced shifting is that the cables don't run through the tubes' centers and that the shift lever will migrate bit by bit with each cycle of flex. I've mentioned this for years and back when screwed and glued AL frames were just coming onto the market came up with the proof test.

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
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