shifter/derailleur stuck in first gear

m00nbadger

Had a bit of problem when i was out on the bike today. Hadn't ridden it for a few weeks and all was well then. Cleaned it yday then went to Llandegla today

When it first gear, I'd move the trigger shifter to go down through the gears. trigger was working as normal with no different feeling, but the derailleur wasn't moving. went back up/down the gears a few times but was till stuck. managed to free it by going all the way down to 10th (the highest gear/smallest cog), and then worked fine. as long as I didn't go back into first (as when I did it happened again)

Any ideas on what the problem could be, and/or where I should start trying to look to fix things?

Cheers

The Rookie

To clarify, first gear is the largest sprocket, from there you can only go UP through the gears not down, so you are saying it was getting stuck on the largest sprocket?

First check is the cable, is it going slack as you shift up? If it is then it's nothing to do with cable or shifter, if it isn't then it's nothing to do with the mech.

LimitedGarry

Just guessing here, might be the mech is too far from the cassette (try messing with the third not-sure-what-it's-called screw). Might also be too high cable tensions. Might be a cassette problem (but unlikely).

If I understand your problem correctly, you're unable to shift up from your lowest gear unless you shift all the way up to the smallest gear? That seems like a pretty odd problem, because from experience, the mech will not physically move there (at least shouldn't) because the chain doesn't have enough flexibility. The only exlanation I can think of is the cable tension being too high, but you'd notice that across the entire range of your cassette. Bent hanger also causes issues and typically for very specific sprockets, but that still doesn't explain why it gets stuck on the first gear and doesn't shift higher unless you go all the way to the lowest gear.

If you're able to, post a video. Or at least a picture of your mech and cassette. Anyways, this doesn't sound to me like a problem with something not adjusted properly, but rather something screwed up beyond recognition. I've had some mishaps when it comes to wrong adjustment of the rear derailleur in the past (learning curve) but never anything like this.

The Rookie

Garry is referring to the b-screw.

m00nbadger

so to explain a bit better, when on the largest sprocket and you shift to go up through the gears, no gear change happens. looking at the derailleur when changing gears, it doesn't move. when I shift all the way up into the smallest sprocket it seems to burst into lift and work again, however I'm thinking this is more to riding and the bike being jolted about maybe

once out of the largest sprocket shifting up/down through the gears is completely as normal, so thinking it is possibly related to the cable tension. however, not sure what I'd need to do so any ideas would be welcomed. will try get a video made if that would be of use too

thanks

JBA

Try winding the B screw in a couple of turns. If it is out too far the top jockey wheel could be too close to the sprocket and hold the rear mech in place when you try to shift up a gear.

cooldad

If you've checked the b screw and it hasn't helped.
Disconnect everything, clean and lube the mech, clean (or preferably change) the cables.
Read Parktools and index properly from scratch.
If that doesn't work it's new bike time.

FishFish

Also check the L screw - It may be limiting the chain too far 'in' and thus slightly off the lowest / largest cassette cog and maybe inhibiting its return as a result. The cable is used to pull the gears into lower gears and the spring returns them to a higher gear so have a look at that. If it is a 2x or 3x then look at the chain line - actually don't - but lube the chain a bit more.