Cycling UK Forum

I've a set of Stronglight (triple rings) largest 52 which will not change to largest ring.

Any ideas?

I've tried the usual adjustments and it gets very close rubbing on the ring but will not transfer -I had a similar episode a few years back and then seemed to sort it by juggling about with it.

Its not v.worn and reasonably well maintained I know I can take it to a local bike shop who'll bung it on a stand sort it and then a little while later when trying to change back up it won't go,

Any ideas?

Thanks in advance

What do you call the usual adjustments?

What's rubbing on the ring? If it's the front derailleur, then has it slipped down the seat post?

Could the front derailleur have been knocked? Is it still in line forwards-backwards?

Its the chain - having visually checked the front derailleur its not moved or been knocked I suppose it could have slipped but I can't prove it has or not

Although agree with mjr most likely its been knocked check its still parallel. have you changed the BB, is it the right length?

Hang the bike -up so the rear wheel is off the ground

turning the pedals pull cable by hand does it pull the mech far enough across i.e is enough to shift it just past the ring , look for if its pushing the chain at the right place.
do you have any adjustment left in the end stop ? (H screw)

has the current set-up worked in the past ?

The current set up did not work until 3-4 years ago when the tweiddling sorted it- its needed occasional fine tuning since then but has moved far enough across to take the chain onto the largest ring.

I think theres just about enough clearance to get it onto the largest ring but it will not move across - it it once last night but would not replicate it- very frustrating

What do you call the usual adjustments? Have you tried resetting the cable tension? When did it last have a new cable? Is it sticking or worn or corroded anywhere?

Its not sticking is not worn and the cable is about as tense as it can be

Limit screw?

If it is the limit screw which has slipped surely the problem is likely to re-occur?

I've used adjustment of the limit screw previously, to enable the derailleur to move dar enough across only for this to slip back-I've been using an adjuster in the middle of the cable ( by where the gear shifters on the down tube used to be for those of us preflight deck shifters- this has worked so far.

Its also a damn site easier to use than index screws

What is your model of shifters and front mech? Is the cable clamped correctly and firmly enough at the front mech that it can't slip under load? Is the front mech clamped parallel to the chainrings and at the correct height? It could also be too low and the inner cage plate could be grinding on the middle chainring even though the outer plate is clearing the teeth of the big ring. This would stop the cage from moving over far enough to allow the chain to engage big ring. Can you change into the big ring by pulling the front mech cage out with your hand while pushing the lever where the cable is clamped with your thumb (thereby isolating the action of the derailleur from the cable and shifters)? If you can't it might be a limit screw adjustment, positioning of the front mech or chainline issue. If you can get it to change by shifting at the front mech with your hand then it's likely to be a shift lever/cable problem. Have you got any in line cable adjusters? I had some that kept winding themselves back as the bars turned. Also check that your front mech cage isn't bent out of shape. It might be helpful to post some photos of your setup.

QUIST wrote:If it is the limit screw which has slipped surely the problem is likely to re-occur?

I've used adjustment of the limit screw previously, to enable the derailleur to move dar enough across only for this to slip back-I've been using an adjuster in the middle of the cable ( by where the gear shifters on the down tube used to be for those of us preflight deck shifters- this has worked so far.

Its also a damn site easier to use than index screws

But surely they don't do the same adjustment. The limit screw is a "stop" whereas your other adjuster is a cable length adjuster. Does or can the FR move so it's over the top of (and parallel with) the large chain wheel?

It will not move all the way across just beiny a teeny bit short but this is how it was previously and I sorted it out by fiddling withe cable adjuster not the stop. And as I said it an earlier post it moved straight across earlier this week but would not repeat the action when I tried it again

What is the FR?

Taking it from the top.
If the mech has the required amount of clearance between the outer cage plate and outer ring,about 3mm,and if the outer cage plate is parallel with the outer ring.
Either the cable isn't pulling the mech over far enough or the the H limit screw is preventing it doing so.
I'd recommend initially slacking off the H limit screw 1/4 of a turn and see if it helps,if not tighten the cable adjuster to pull a little more cable,or both.
If the mech is at full stretch ie; as far as it'll go with the H limt screw slacked off fully,and still not shifting the chain over onto the big ring,then you need either a shorter BB axle,or a different more suitable mech.
It could even be a matter of a excessively worn chain having really bad side slop,though TBH that's really an outside chance.

I'm pretty certain it ain't an excessively worn chain.

On the basis that the Stop is unlikely to slip that rules that out.

I still think the potential problem and solution is with the cable after all by adjusting the cable stop previously I managed to solve the problem although like now it was very frustrating that it was so close but would not mobe onto the largest ring

have you checked and cleaned the mech to make sure there is nothing stopping the full movement? if you undo the cable can you move the mech all the way by hand?
has all the cable adjustment been used?