Joined: Feb 2012
Posts: 19,381
Likes: 5,527
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
So a new cassette and rear der with old chain?
If so first thought is a chain/cog wear miss match skip. With the longer cage but the same length chain the cage will rotate so the guide pulley is further from the cog's undersides when in the middle ring, compared to the granny ring. And when in the large ring the entire der gets pulled forward. So in both large and granny the chain can wrap further around the cogs. Just speculation. But a new chain is an easy try and what most will say should have been replaced when the cassette was. Andy
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AndrewRStewart