Bicycle Mechanics - Shimano STI Shifter - Cable Return Problem

My Specialized Allez is about 3 months old and has only a couple hundred miles on it, but those are miles on bumpy Boston city streets. The left shifter, which is a Shimano ST-4500 in the Tiagra groupset, seems to be not returning the cable at all. When I try to shift onto the larger chainring, the shifting lever just stops about halfway through its travel and the derailleur does as well.

The derailleur moves just fine, so it isn't a limit/cable tension issue. I can plainly see the head of the cable being slightly buried in the little window on the side of the shifter, and I understand the head should be plainly visible there.

For now, I've unhooked the cable and just limited out the derailleur so I can ride with the chain on the large ring. Ideally I'd like to fix this problem myself so that I don't have to be without transportation for too long. Does anyone have any experience with this kind of problem?

Thanks so much!

I would just bring it in if the bike is that new. If the brifter is the problem you won't be able to fix it yourself, in fact the shop won't be able to either. Shimano brifters are not field servicable.

Possible the cable is hung up inside, or there is gunk in the shifter. Removing/replacing the cable and flushing the innards with wd-40 or suchlike are good first steps.

Beyond that you're getting into disassembly, which is possible if you're careful (tip: on reassembly use a piece of dental floss to pull the end of the return spring in place), but finding replacement parts is hard.

i must concure with the above. besides checking to see if the problem lies in the shifter cables/housings, also check to make sure your derailleurs are adjusted right. if the shop you got it from will look at it for you, as any good shop would follow up, i'd do that. and sad but true, shimano sti brifters are not user servicable, like prev. mentioned.

Thanks a lot for your help, everyone. After taking off the rubber covering of the shifter, I took one look around in there and decided not to get involved. :) It's covered under warranty at my shop, so hopefully a replacement shifter is in order. I wonder what happened?

Possible the cable is hung up inside, or there is gunk in the shifter. Removing/replacing the cable and flushing the innards with wd-40 or suchlike are good first steps.

+1.

Cables that tear themselves apart in any fashion are not fun to deal with.

I'd take the cable out, and try to operate the brifter cable-less, if you can, to pinpoint the issue to either the cable or the brifter.