My rear derailleur has started skipping gears and balking when shifting; since I bought the bike four years ago, I assume it's a stretched shifter cable. Trouble is, since the bike was new it's always dropped the second cog when shifting up – that is, when passing from third gear to second, it's always hesitated on second for a few cranks, then spontaneously fallen down to the highest gear. When I shifted back to second it would calm down and stay put. This was the only shifting problem I had until now.
Because I seldom use those gears and prefer riding to tweaking, I just lived with it. But now I find myself wondering if the assembler cut the cable housing to the right length, since I'd have to remedy that if I expect a new cable to solve the whole problem. The loop at the derailleur has always seemed flat; most bikes have a nice graceful curve there. (See photos, taken in highest and lowest gear.)
I'd appreciate any input on this issue. Could a too-short housing have caused the original spontaneous shift from second cog to first? For that matter, do you agree that the problems I'm having now are probably down to an old, stretched cable?
Thanks.