Front derailleur not staying on big ring

[Tigerbiten]

If the derailleur moves easily when you move the lever but doesn't stay to where it's moved to then it sounds like the ratchet in the shifter that keeps the derailleur on the big ring isn't catching.
I'd take the cable off the derailleur, pull it tight by hand and try various shifts both up and down.
Can you feel the ratchet catch when you shift up and let go when you shift down ??
If you can feel it working then it comes down to cable adjustment.
If not then you may have a dead shifter ......

Luck .............

 

[boydj]

You can see why people get confused, one opinion the cable needs tightening, one the cable is too tight!

But some of us may have done this job several times and know what we're talking about - after figuring out very similar problems to the OP.

A too tight cable is a much more likely problem than a broken shifter and should certainly be eliminated as the source of the problem first.

 

[Svendo]

A possible approach might be to go to Shimano Tech docs, get the instruction, disconnect the cable and start from the beginning. This is the list and the 2 beginning 5 are the FD instructions.

 

[Chislenko]

But some of us may have done this job several times and know what we're talking about - after figuring out very similar problems to the OP.

A too tight cable is a much more likely problem than a broken shifter and should certainly be eliminated as the source of the problem first.

I think you missed the point of my post!

 

[Paulus]

My twopennence worth is that the cable could be a little too tight so not allowing the shifter ratchet to move enough to hold the cable on the large ring.
Shift to the smaller ring and check that there is a bit of slack in the cable
If not , loosen the cable clamp on the front derailuer and slacken the cable and take it from there.
It has already been said that if the limit screw is not allowing the mech to go far enough over, this would also have the same effect.

 

[Ajax Bay]

when you've released the cable, to pull it taught and operate the shifter to make sure it's functioning correctly so that can be ruled out.

This: check the shifter's operating first: click up and click down, with hand tension on the cable.

some of us may have done this job several times and know what we're talking about - after figuring out very similar problems to the OP.

A too tight cable is a much more likely problem than a broken shifter and should certainly be eliminated as the source of the problem first.

Some of us! Second sentence: agree. But (based on the OP) as for your deduction: do not agree, Boydy, see @Cycleops - "done this job several times and knows what he's talking about"! First check the shifter works.
How would a "too tight cable" result in the cage shifting to the lower ring, pray?
Anyway, FD cable tension is dependent on the spring strength in the FD and its geometry. Cable tension does not shifter the cage per se, cable movement (or not) effected by the STI does.

 

[I like Skol]

How would a "too tight cable" result in the cage shifting to the lower ring, pray?

If the shifter can't make it to the first click before the stop screw prevents further movement then the cable is too tight and the shifter will just drop back to the small chainring.

 

[Ajax Bay]

If the shifter can't make it to the first click before the stop screw prevents further movement then the H limiter screw is too far in and the cage will just drop back to the small chainring.

FTFY Nothing to do with cable tension, the pawl in the STI is not engaging, iyswim.

 

[I like Skol]

FTFY Nothing to do with cable tension, the pawl in the STI is not engaging, iyswim.

No, I was right first time thank you. If the cable is clamped too short (or too much tension as people like to say) then the stop screw can be in the correct position but the shifter will be unable to reach the click (or pawl as you quite rightly say).