After 4,863 miles of shifting nirvana (5,217 total miles on my Di2 drivetrain), today I had a bad shift.  I’ve grown so accustomed to absolutely perfect shifting with Ultegra Di2 that this was a rather soul-wrenching experience.  The reason I don’t have 5,217 perfect  miles is that it took me a little over 300 miles in the beginning to figure out that Di2 is less forgiving of lateral chain sway than a conventional drivetrain.  Once that was solved, Di2 has been a dream.  What follows is the reason my record of perfect shifting ended today.

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