Hi during a roubaix style race yesterday my gf's bike stopped shifting
she has a devinci road bike with 8 speed
I'm unable to make it shift even by pulling on the cable
the cable has lots of slack in it but does tighten up when I use the brifter and will develop slack again
I've already cleaned the bike and can't find anything jammed up
I'm going to start by replacing the cables but if that fails... I think her Sora RD might be shot though
Lets see if I understand this correctly:
We`re looking at a DeVinci with an 8 speed drivetrain and Shimano Sora rear derailleur that suddenly has become seized in top gear? And you think the derailleur is shot but want to start checking that by replacing the cables?
Suggest you start by disconnecting and removing the rear derailleur. If the derailleur is really siezed you won`t be able to flex it off the bike either. But a seized rear derailleur mechanism is fairly rare and is usually caused by corrosion - in which case you`d also likely have corossion issues with other parts of the bike too.
And since it just recently happenned I suspect it might be cable or shifter related and I`d suggest you start by checking the condition of those as well before you start replacing things. The cable should slide freely through the housing and the brifter should progressively provide cable pull.
Whichever doesn`t happen should teel you where the issue is.
Sounds like the cable is simply sliding through the clamp. First try if you can push the derailer sideways with your hand (Not too far though, mind the chain. If you want to be ultra-certain of not doing any damage, remove the wheel first.) If the derailer can move sideways, undo the clamp, take up the slack (make sure brifter is in high gear) and tighten clamp again. Now try shifting again. It'll probably be quite out of tune, but there should be some shifting action.