Originally Posted by
whitehare
To FBinNY
The shifting problem is on my brand new 2015 GT Grade tiagra. When they built it the mechanic supposedly spent an hour setting up the derailers and when I took it out for a quick 2 mile test ride I noticed the the shifting in the rear would sometimes not shift and sometimes would shift 2 gears at once. They said it has to due with the shift cables being fully sheathed and it should break in.
Baloney! Fiddling with the derailleur for an hour on a new bike tells me that the mechanic hasn't figured it out. If you brought that bike to me the first thing that I would do would be to check the derailleur hanger alignment. It doesn't have to be off by much to make it act exactly like you indicated. It's possible, of course, that hanger alignment isn't the problem but, when I was doing a lot of that type of repair, I found I was time ahead by checking that first.