Shifting Problem (Part 4)

[nmfeb70]

Hi all, so, here we go again...

My shifting has been a bit stubborn of late, the chain refuses to lift up onto some sprockets and when I slightly adjust the cable tension to shift up it won't drop back down. Despite the cable being three months old I decided to replace it along with the housing, but it still persists on giving me a headache. This morning I started from scratch, I undid the cable, manually moved the RD up & down onto every sprocket, no problem there. I washed and cleaned the cassette, chain, RD and lubricated the RD pivots, I then inserted a new, lubricated cable and indexed the shifter. What could possibly go wrong? Well, the chain refuses to play ball yet again. It doesn't even attempt to move up to the third & second largest sprockets and won't drop back down after cable adjustment.
The RD clicks into position every time so am I correct in narrowing it down to a worn chain not catching onto the teeth? A few members indicated my chain may need replacing in an earlier post. Any suggestions? Thanks.

 

[fossyant]

Your hanger maybe bent, does the mech cage hang down parallel to the wheel ? Even from new, hangers can be a little out of 'straight'.

You can bend them back carefully, but if it's very bent, you need a new one.

 

[Tenacious Sloth]

Disconnect the end of the cable from the rear derailleur.

Then, while gently pulling the cable to simulate the force normally exerted by the derailleur spring - move your shifter to the highest gear (which should allow you to pull the cable to it’s maximum length).

It helps to have the arm span of a gorilla When doing this. 🙂

Still pulling on the cable, move the shifter through the full range of gears. You should be able to feel the shifter pulling the same amount of cable for each click.

Is the correct amount of cable being pulled when you get up to the lower, problematic gears? It may be clicking, but is it pulling the correct amount of cable?

If not, then it’s a problem with your shifter. Have you had a cable break or fray within the shifter previously? If so, then some of the old cable is still inside the shifter and needs extracting. This is a common problem with the newer Shimano shifters that run the cable out the back and under the handlebar tape due to the tight angle change for the cable within the shifter.

If your shifter is retrieving the correct amount of cable, then the problem lies elsewhere and at least you know your expensive shifter is ok.

 

[nmfeb70]

Your hanger maybe bent, does the mech cage hang down parallel to the wheel ? Even from new, hangers can be a little out of 'straight'.

You can bend them back carefully, but if it's very bent, you need a new one.

I forgot to mention in my post that I replaced the hanger but it didn't solve the problem.

 

[I like Skol]

Could be lots of things....

When you changed the cable outer, do you mean the bit at the rear mech or all sections from shifter to mech?
Is the cable seated and routed correctly within the shifter?
Does the cable run through a plastic guide under the bb? These can get cut/grooved after a time and prevent the cable from sliding freely. A hack I recently came up with is to dismantle a piece of cable outer and extract the liner tube. Use a section of this slid over the inner cable and rest it in the bb guide. It can transform the cable freedom.
Is the top jockey wheel badly worn and wobbly? This will also have a marked effect on gear selection.

 

[Arrowfoot]

Hi all, so, here we go again...
.. I slightly adjust the cable tension to shift up it won't drop back down....

If it won't drop back, it means the cable tension is insufficient when the screw was tightened.. Earlier problem could be the cable slipped due to the screw not been tightened properly.

Release the cable from the RD screw. Bring the chain to the lower cog and highest chain ring, turn the barrel adjuster inwards until the end. Then turn it out by 2 complete turns. Pull the cable and tightened under tensio, it will be slight pressure. No hard pull. Then use the sifters to raise it a few cogs higher and bring it back down again. No need to go all the way to top. If it does not work for the first few, it would not work for the others. Use the barrel adjuster to fine tune it.

Worst case scenarios are with the RD spring no longer working or the jockey wheels bent, both very unlikely.

 

[All uphill]

I forgot to mention in my post that I replaced the hanger but it didn't solve the problem.

Did you use a hangar tool to check that if is exactly parallel to the wheel?

As @fossyant says they are not always perfectly straight even when new.

If there is even a little misalignment you can get poor shifting.

 

[nmfeb70]

Could be lots of things....

When you changed the cable outer, do you mean the bit at the rear mech or all sections from shifter to mech?
Is the cable seated and routed correctly within the shifter?
Does the cable run through a plastic guide under the bb? These can get cut/grooved after a time and prevent the cable from sliding freely. A hack I recently came up with is to dismantle a piece of cable outer and extract the liner tube. Use a section of this slid over the inner cable and rest it in the bb guide. It can transform the cable freedom.
Is the top jockey wheel badly worn and wobbly? This will also have a marked effect on gear selection.

The cable housing runs entirely from shifter to rear mech with no kinks or obvious obstructions. I will check the guide pulley.

 

[nmfeb70]

If it won't drop back, it means the cable tension is insufficient when the screw was tightened.. Earlier problem could be the cable slipped due to the screw not been tightened properly.

Release the cable from the RD screw. Bring the chain to the lower cog and highest chain ring, turn the barrel adjuster inwards until the end. Then turn it out by 2 complete turns. Pull the cable and tightened under tensio, it will be slight pressure. No hard pull. Then use the sifters to raise it a few cogs higher and bring it back down again. No need to go all the way to top. If it does not work for the first few, it would not work for the others. Use the barrel adjuster to fine tune it.

Worst case scenarios are with the RD spring no longer working or the jockey wheels bent, both very unlikely.

It shifts through the smallest sprockets fine until I adjust it to move it up into the larger ones (notable 2 & 3). Then it won't shift back down through the high gears (8 & 9).

 

[Arrowfoot]

It shifts through the smallest sprockets fine until I adjust it to move it up into the larger ones (notable 2 & 3). Then it won't shift back down through the high gears (8 & 9).

That stumped me. My guess is there is a kink along the route and the cable gets stuck once it passes the point of the kink as you raise it pass 8.

 

[raleighnut]

I forgot to mention in my post that I replaced the hanger but it didn't solve the problem.

Even a new hanger needs aligning to the bike/wheel.

 

[I like Skol]

Don't get obsessed by hanger alignment. Unless it is badly out it really only causes niggly noisy running and the occasional poor shift. In some set-ups not even that, and a small tweak in any direction is not noticeable. What the OP is experiencing is unlikely to be caused by sub-optimal hanger alignment, there is something else at play here.

 

[andrew_s]

Have you got one of those arse about face "rapid rise"/low normal rear mechs that used to be popular?

These are sprung to the largest sprocket, and use the cable to pull the mech down to the smaller sprockets. This means that the change on to the largest sprockets is powered by the mech spring at the weakest end of its travel, and that sticky mech pivots or something would give the reported symptoms.

 

[nmfeb70]

Have you got one of those arse about face "rapid rise"/low normal rear mechs that used to be popular?

These are sprung to the largest sprocket, and use the cable to pull the mech down to the smaller sprockets. This means that the change on to the largest sprockets is powered by the mech spring at the weakest end of its travel, and that sticky mech pivots or something would give the reported symptoms.

It's a "regular" Shimano Alivio RD where the cable pulls the mech to the largest sprocket and releases it back to the smallest. I have washed, cleaned and lubricated the mech & it's pivots but to no avail.

 

[neil_merseyside]

The cable housing runs entirely from shifter to rear mech with no kinks or obvious obstructions. I will check the guide pulley.

That's a long outer run with lots of friction, outer cables are usually just handlebar to downtube, then bare cable until the short outer at the rear mech.