105 rear derailleur seems reluctant to shift up...

[Wobblers]

The rear mech on my Cannondale doesn't seem to want to change up gears. It'll shift down without any problems. Changing back up is a different matter: the first 3 clicks on the shifter are fine, but after that it doesn't change immediately the lever is pressed - but does often then change up after a delay of some seconds. Irritatingly, there were no problems with the gears the last time I used the bike back in early November [1]. Cable tension seems to be fine, and the cable moves freely through the guide on the bottom bracket. The STI shifter seems to be working fine: at any rate, the ratchet pays out the right amount of cable with each click of the lever.

It almost feels like the problem is in the tension spring in the rear derailleur. But it - the whole bike, in fact - is less than three years old: surely it should be expected to last longer? Is there anything else I should be looking at?


[1] Obligatory excuse: tendonitis in my knee has kept me off the bike: it's been a long four+ months...

 

[slowmotion]

I think that the rear derailleur spring is very unlikely to be the problem. Torsion springs don't suddenly get tired, they work or fail completely. Is the rear mech reasonably clean and well lubricated? It could be a pivot that's a bit iffy. My best guess is that the gear cables are sticking somewhere between the shifters and the mech.

 

[R600]

is it possible that the rear mech has been knocked while in storage, poor shifting in my experience is usually down to poor alignment of the rear mech or the inner cable isn't running smoothly in the cable outer. i recently purchased a new winter frame and could not get good shifting through all gears, it turned out to be the rear gear hanger was out of alignment, once straightened shifting was spot on every time.

 

[ianrauk]

New cable needed I reckon..

 

[robjh]

If you push the derailleur forwards by hand, does it spring back properly to its tensed position? I had a 105 rear mech where the pivot where it screws into the dropout would stick, preventing the mech from reverting to its correct position when I shifted up (reducing chain tension). I concluded it was completely gunked up, but in fact unscrewing and refixing it made all the difference.

But I would still think that cable and cable housing - especially the bit that bends round to the rear mech - are the first candidates to look at.

 

[e-rider]

The rear mech on my Cannondale doesn't seem to want to change up gears. It'll shift down without any problems. Changing back up is a different matter: the first 3 clicks on the shifter are fine, but after that it doesn't change immediately the lever is pressed - but does often then change up after a delay of some seconds. Irritatingly, there were no problems with the gears the last time I used the bike back in early November [1]. Cable tension seems to be fine, and the cable moves freely through the guide on the bottom bracket. The STI shifter seems to be working fine: at any rate, the ratchet pays out the right amount of cable with each click of the lever.

It almost feels like the problem is in the tension spring in the rear derailleur. But it - the whole bike, in fact - is less than three years old: surely it should be expected to last longer? Is there anything else I should be looking at?


[1] Obligatory excuse: tendonitis in my knee has kept me off the bike: it's been a long four+ months...

when you say 'up and down' the gears, can you clarify which direction exactly?
This sounds like a really easy problem to solve.
If you are having trouble going from larger sprockets to smaller sprockets (i.e. to a higher gear) then that is probably the cable that needs replacing as it will not be running smoothly inside the outer cable.
If you are having trouble going from smaller sprockets to larger sprockets (i.e. towards a lower gear) then I suspect that the cable has stretched a fraction - just turn the adjuster on the rear mech by 1/4 or 1/2 turn (anticlockwise)

 

[Wobblers]

Thanks for the replies.

It doesn't miss a beat when shifting to the larger sprockets, so I don't think the indexing is awry (first thing I checked). The trouble only occurs when changing up gear to the smaller sprockets. The gear cable seemed to move freely when I checked it, though of course that doesn't mean it doesn't need replacing, and it does seem the most likely cause. Does needing a new cable after 2-3000 miles seem reasonable? I'd kind of hope to get more miles...

 

[slowmotion]

Does needing a new cable after 2-3000 miles seem reasonable? I'd kind of hope to get more miles...

There are an awful lot of variables. I don't think that 2-3 thousand is totally awful, just slightly disappointing. I find that if a bike is unused for a length of time, the gremlins creep in for no obvious reason. I have no idea if that's the case with yours. Good luck.

 

[e-rider]

Thanks for the replies.

It doesn't miss a beat when shifting to the larger sprockets, so I don't think the indexing is awry (first thing I checked). The trouble only occurs when changing up gear to the smaller sprockets. The gear cable seemed to move freely when I checked it, though of course that doesn't mean it doesn't need replacing, and it does seem the most likely cause. Does needing a new cable after 2-3000 miles seem reasonable? I'd kind of hope to get more miles...

this would depend on the quality of the cables, whether they were greased when fitted, how much rain you've ridden in, length of time they been on your bike etc, not so much total mileage - you could ride 3000 miles in 6 weeks and they'd be perfect, ride 500 miles over 5 years and they will need replacing!

 

[gwhite]

First check would be to undo the cable and the turn the cranks and see if the chain now moves to the smallest cog. If it does so then the problem usually lies with the cable requiring cleaning with the increased friction being usually found at the cable loop before it enters the RD. If replacing the outer cable housing ensure that this is long enough to enter the RD opening without being at an angle.

 

[rb58]

I'd suspect cable too. That last loop before the derailleur gets a lot of road debris thrown at it which can cause it to get gunked up.