Front Shimano derailleur not shifting up

[billwoods]

Hello

Looking for a bit of advice/knowledge if possible, i got hold of a second hand MTB , its a decent bike but there is an issue with the front derailleur not moving up, basically when you go from 1 to 2 there is very little resistance on the lever and hardly any tension on the cable, the derailleur moves outwards but then springs back a little and does not change gear, however when going from 2 to 3 there is resistance on the lever, tension on the cable and the gear change occurs but only on to the second cog, the derailleur also moves over and stays solidly in place.

I have checked the indexing, alignment, limit screws and messed around with cable tension both at the barrel and at the cable locking nut but no success at all, i am thinking that the issue must be with the shifter, maybe needs cleaning but cant work out why the change from 2 to 3 on the lever works perfectly "although only moving to 2) whilst going from 1 to 2 seems so slack ,will not shift and springs back when the lever is released.

Anyone any ideas/suggestions ?

Thanks

 

[Big John]

If you bought it second hand have you replaced all cables? You may even have to replace cable outers too if they look old and manky. I'd start with that. There are a multitude of YT vids that'll show you how to resolve front mech issues.

 

[cyberknight]

If you bought it second hand have you replaced all cables? You may even have to replace cable outers too if they look old and manky. I'd start with that. There are a multitude of YT vids that'll show you how to resolve front mech issues.

indeed , sounds like the cable needs replacing and set up from scratch as there shouldnt be any slack in the cable to start with .

 

[Punkawallah]

I would take a picture of the front derailleur cable route.
Then put the chain in the smallest cog, front and back; screw any cable adjusters for the front derailleur down; release the cable from the front derailleur; remove the cable from the cable outer and clean it with some fine wire wool and 3-in-1 or similar.
Squirt some WD40 or similar into each length of cable outer; replace the cable in the cable outer and re-attach to the front derailleur (use picture for reference); try the gear changes again.
If you get the same results, the limit screws might need adjusting to bring the front derailleur cage closer to the chainring, which means the cable will have to be released and re-attached.
Good luck :-)

 

[raleighnut]

Insufficient cable tension, when you shift front cogs the mech should move out then on releasing the lever retract slightly to give clearance. I'd take most of the slack out of the cable then 'fine tune' the cable so that when 2 is selected the mech is central on the middle sprocket and chain when the shift lever is released.

 

[billwoods]

Hi all

Thanks for the replies, it was indeed a cable issue, a new cable fitted and everything now set up, indexed and working perfectly

Thanks for the advice as a cable would have been and actually was the last thing i would have thought of

Cheers

 

[raleighnut]

Hi all

Thanks for the replies, it was indeed a cable issue, a new cable fitted and everything now set up, indexed and working perfectly

Thanks for the advice as a cable would have been and actually was the last thing i would have thought of

Cheers

With a triple up front cable condition and tension are critical, the only 'indexing' for the middle ring is cable tension. Inner and outer rings are controlled by the limit screws but the middle is just 'floating'.

Oh and BTW the cable will probably need tweaking after a while as it 'hardens off' and settles down, some people call it stretching but as @Yellow Saddle will point out they don't 'stretch' as such but the individual strands snug down against each other under the effect of tension.

 

[Yellow Saddle]

Oh and BTW the cable will probably need tweaking after a while as it 'hardens off' and settle

 

[Yellow Saddle]

Yellow Saddle disagrees. Steel cable on bicycle applications doesn't snug down. Reason being that for that to happen, the steel has to be stretched beyond the point of yield. Forces in gear shifters or gear levers are too small for that. There is no elongation from repetitive use at all. What does happen is that the cable abrades the inside of the housing, specifically the inside of the arc formed where the cable makes a bend, such as the 270 degree loop at the rear derailer. Once the inside abrades, the effective length between inner and housing changes. Essentially the inner takes a shoortcut by cutting corners. This makes the inner effectively longer and makes the gears/brakes out of tune.

 

[Punkawallah]

I can see the logic behind this.

 

[Mike_P]

My bodge on a triple front is to use a suitably sized piece of wood to hold the derailleur in line with largest chainwheel and then tighten the cable.

 

[Ajax Bay]

BTW the cable will probably need tweaking after a while as it 'hardens off' and settles down, some people call it stretching

This post-installation and a quick ride check is needed, not because the steel cable 'stretches' but because one or more of the several interfaces between the cable outer/ferrules and the stops (or inside the STI/Ergo or at the RD) may not have been fully seated. A bit of operation will force that and then maybe @raleighnut 's tweaking is required (always tightening).

 

[Gwylan]

My bodge on a triple front is to use a suitably sized piece of wood to hold the derailleur in line with largest chainwheel and then tighten the cable.

Sounds like my approach.

Dumbo question: are all cables equal? Can I buy one long length to fix the derailleurs and the brakes?
Or?

Asking for a friend, of course

 

[Alex321]

Sounds like my approach.

Dumbo question: are all cables equal? Can I buy one long length to fix the derailleurs and the brakes?
Or?

Asking for a friend, of course

Ignore what I said, it seems I was wrong.

 

[Punkawallah]

Sounds like my approach.

Dumbo question: are all cables equal? Can I buy one long length to fix the derailleurs and the brakes?
Or?

Asking for a friend, of course

There are at least two types of cable, gear and brake, with different mounts for different levers. I understand you can get a brake cable with MTB fitting at one end, and road fitting at the outer, where you cut off whichever is not needed. The cables come in standard lengths, which you cut to size.