Nightmare with changing between the front chainrings

[Roadhump]

I hope somebody is kind enough and patient enough to read this lengthy explanation and perhaps offer me the benefit of their advice / wisdom/ mechanical expertise.

I am having a nightmare with the front mech / chainring on my 5 year old Sirrus Pro. I posted this a few months ago, but the problem persists

https://www.cyclechat.net/threads/problem-with-front-derailleur-gear-shifter.226433/

The main problem now is that the chain will not shift to the large front chainring. 2 separate mechanics, working for different places have taken it for repair (one about 3 or 4 times), told me they have repaired it and made sure the shifters work, but each time I take it back, the chain moves to the big ring the first couple of times I have tried it, but then stops doing so.

It seems to work okay when in a stand but as soon as I ride it, under load, it stops operating properly.

The latest attempt involved fitting a better quality chainring, but the same thing happened.

I am beginning to think it might be time to give up on the bike, but it is only 5 years old and I would have thought it would have much more life left in it yet.

Perhaps before doing that, it might be worth systematically changing each component, or just the whole lot, but that could end up with money wasted.

I also wondered if it could have something to do with my weight, which at 15 stones, isn’t inconsiderable.

Any advice gratefully considered.

 

[gbb]

Given the weather and particularly the salt on the roads, this time if year is hard on bike components.
Do you feel confident enough to take your front derailleur cable off ?
Then you can check to see the pivots aren' seized and that the next swings enough between the two chainrings.
I had the old Sora 8 speed FD and this time of year...every year...it would seize exactly as you describe. I can't see what yours is like but on Sora the pivot was a dome headed bolt. When mine seized you could tell straight away...I simply undid that bolt a little...not right undone, worked the mech and applied WE 40 liberally to the pivot. Worked every time.
Something worth checking. Even if there's no bolt at the pivot...say just a rivet type pivot...you can still lube it.

Scrub that I see it works on the stand.

 

[gazza1286]

There's no reason why the front mech should be always 'under load' just because you're riding. Will it not change at all if you're riding?
Is there any scope to reduce the outer limit screw to the point where the outer plate catches only on the 11 sprocket? If that then allows a smooth change either live with it or incrementally let the outer limit screw back out.

 

[derrick]

Got a pic of front derailier? what is the frame made of?

 

[Roadhump]

It is an alloy frame. The front derailleur still moves over the outer ring, it's just that the chain doesn't move properly. There is a noise so you can tell the chain is rubbing against metal, which goes as soon as you shift back to the small ring position.

 

[Roadhump]

When I took it out earlier, after collecting it from the LBS, I tried adjusting the cable with the shifter barrel adjuster which helped, but it just reverts back to not moving after a couple of shifts. I also tried giving the out limit screw a 1/4 anti-clockwise turn, but that didn't help. Eventually I snapped the cable so it's back to the LBS next week anyway.

 

[derrick]

Is it band on or brazed fitting?

 

[wisdom]

Bit of a long shot.
Is the new chainring you fitted compatible with your drivechain as they do have cutaway and little studs to aid shifting.

 

[robjh]

When I took it out earlier, after collecting it from the LBS, I tried adjusting the cable with the shifter barrel adjuster which helped, but it just reverts back to not moving after a couple of shifts. I also tried giving the out limit screw a 1/4 anti-clockwise turn, but that didn't help. Eventually I snapped the cable so it's back to the LBS next week anyway.

Are you saying that you tighten it, it shifts OK for a bit then stops, so you tighten it again, it works again for a bit, and so on?

Also, where did the cable snap?

I'm wondering if you had a fraying cable, which was gradually stretching as it frayed. I once had that with a cable that was rubbing and fraying inside the brake lever assembly, and the first symptom was that it needed constant adjustment. If that was indeed your problem, then a new cable should fix it.

 

[Roadhump]

Bit of a long shot.
Is the new chainring you fitted compatible with your drivechain as they do have cutaway and little studs to aid shifting.

I would have to rely on the mechanic to make sure it was compatible. He did say that the lifters (or whatever they are called) that aid shifting, are better on the new chainring, which he says is better quality, no reason to doubt him, he is well regarded in local cycling circles.

As it happens, I have seen an identical bike on Ebay, but it is older than mine (2011 / 2013), and is up for £380, which seems a bit steep as mine cost me £800, although that was reduced by £300 because they had discontinued that style of the Pro version.

I have also seen the Triban 520 and 540 flat bar road bikes for £429 and £449 respectively, so toying with the idea of giving up on this one and going for one of those.

 

[robjh]

I wouldn't give up on a bike just because of a shifting problem. The problem is limited to one set of components that don't affect the rest of the bike, and the solution is likely to be quite simple even though you haven't found it yet.

 

[Roadhump]

Are you saying that you tighten it, it shifts OK for a bit then stops, so you tighten it again, it works again for a bit, and so on?

Also, where did the cable snap?

I'm wondering if you had a fraying cable, which was gradually stretching as it frayed. I once had that with a cable that was rubbing and fraying inside the brake lever assembly, and the first symptom was that it needed constant adjustment. If that was indeed your problem, then a new cable should fix it.

It seemed to respond to a bit of adjustment, but was very hit and miss. It would shift 2 or 3 times and then just rub against the derailleur. I think the cable has snapped inside the shifter because when I move it at the shifter end, it also moves near the mech, I don't want to open the shifter at present because the spring tends to pop out and is a nightmare to get back properly.

Definitely not a worn cable, it was only replaced about 3 weeks ago.

 

[Roadhump]

I was wondering if it could be caused by a new rear wheel. The old wheel rim cracked just before this problem started. Probably not, but the new wheel was not a like for like replacement - same size but different make.

 

[robjh]

It seemed to respond to a bit of adjustment, but was very hit and miss. It would shift 2 or 3 times and then just rub against the derailleur. I think the cable has snapped inside the shifter because when I move it at the shifter end, it also moves near the mech, I don't want to open the shifter at present because the spring tends to pop out and is a nightmare to get back properly.

Definitely not a worn cable, it was only replaced about 3 weeks ago.

If it has snapped then it is definitely worn now! I would want to know how a three week-old cable has been able to snap - there's certainly something wrong there.

 

[roadrash]

have you tried a different shifter