Originally Posted by va_cyclist

New bike with Ultegra10. Shifted very crisply when new, 600 miles later, shifting has become somewhat sloppy. Downshifts are sometimes accompanied by the chain "sliding" as it tries to catch the larger cog; upshifts are generally noisier and clunkier than before; and the drivetrain is overall noisier. It still hits all 10 gears in back, and things in front seem fine. Cable stretch? Time for a tune-up? What's your call?