Is this a symptom of a sticky cable?

[BigonaBianchi]

The rear mech changes fine going down the cogs (smallest to largest) but going the other way( largest to smallest) it skips a lot and randomly, mostly missing 3 or 4 cogs and landing on the smallest cog. I've cleaned the cassette and chain and re lubes etc. I've sprayed gt85 into the cable outers as much as i can and into the shifter an dunder the bottom bracket. I've re tensioned the cable but no matter what i do it just keeps slipping.

The cassette had a larger biggest ring fitted in an attempt to make hills a touch easier without resorting to a triple. I dont know the ratios, but the LBS did it before the LEJOG a few months back.

Ive got a new cable but am loathe to take all the bar tape off if it's not likely a cable issue.

Thanks

 

[john59]

You shouldn't have to take your bar tape off to replace a gear cable. I had problems last weekend with jumping gears and it turned out to be the cable inside the levers, fraying.


John

 

[RecordAceFromNew]

Ive got a new cable but am loathe to take all the bar tape off if it's not likely a cable issue.

If you release the inner at the mech, can you try pulling it at the other end to see if it runs easily within the outer? From the symptom chance is it won't, which means it is a cable issue.

If you are lucky you might be able to get away with just replacing the inner.

 

[BigonaBianchi]

ok chaps thanks...i'll try those.

 

[boydj]

With the cable released from the mech, lift the rubber on the shifter so you can see where the cable is pushed into the shifter. Push the cable from the mech so that the top couple of inches of the cable emerges from the shifter and you will be able to see if the cable moves freely and if there is any fraying inside the shifter. If the cable is ok, then hold it tight at the mech with your fingers and operate the shifter to see if the cable moves freely.

 

[fossyant]

How long have the gear cables been on. Might be time for a complete re-cable ? I reccon the stickyness will most likely be in the handlebar section, as crap eventually gets dragged up the cable !

Test as mentioned above !

 

[BigonaBianchi]

ok...i did all that and then I replaced the cable anyway just in case, even though I saw no kinks or fraying. I re tensioned the cable and the same thing is happening. Major rear end slippage...hmm...i spent nearl 3 hours fiddling with it...the bike i mean...so tomorrow it's back to th eLBS of great expense and much umming and arring...

perhaps a stretched chain??? although it was new in june...but done lejog and lots of mileage since then...does anybody think the larger biggest cog might be a possible cause? it changes fine across the biggest 5 cogs then just slips right over the other 4 to the smallest one...the cable and chain feel slack through the right hand shifter when i change across to the smaller cogs.

 

[phil_hg_uk]

ok...i did all that and then I replaced the cable anyway just in case, even though I saw no kinks or fraying. I re tensioned the cable and the same thing is happening. Major rear end slippage...hmm...i spent nearl 3 hours fiddling with it...the bike i mean...so tomorrow it's back to th eLBS of great expense and much umming and arring...

perhaps a stretched chain??? although it was new in june...but done lejog and lots of mileage since then...does anybody think the larger biggest cog might be a possible cause? it changes fine across the biggest 5 cogs then just slips right over the other 4 to the smallest one...the cable and chain feel slack through the right hand shifter when i change across to the smaller cogs.

When I had problems with my Secteur not indexing properly I took it to the local Specialized Concept Store and they changed both gear cables and Indexed it for £15 so it shouldn't cost you that much to sort it out.

 

[RecordAceFromNew]

ok...i did all that and then I replaced the cable anyway just in case, even though I saw no kinks or fraying. I re tensioned the cable and the same thing is happening. Major rear end slippage...hmm...i spent nearl 3 hours fiddling with it...the bike i mean...so tomorrow it's back to th eLBS of great expense and much umming and arring...

perhaps a stretched chain??? although it was new in june...but done lejog and lots of mileage since then...does anybody think the larger biggest cog might be a possible cause? it changes fine across the biggest 5 cogs then just slips right over the other 4 to the smallest one...the cable and chain feel slack through the right hand shifter when i change across to the smaller cogs.

Let's say there are 9 gears and 9th is highest (i.e. smallest rear sprocket).

If what you are saying is the rear mech/chain go straight to 9th when you shift from 5th into 6th, then likelihood is your shifter is faulty and slipping, which depending on what it is may or may not be repairable.

On the other hand if nothing happens when you shift from 5th to 6th to 7th to 8th etc. but it eventually goes straight from 5th to 9th, then the likeliest cause is sticky cabling system, but if not that (which seems you have established to be the case by now) then two other possibilities are i) rear mech fault (which could be established by feeling whether it is sprung and smooth traversing across the sprockets when without the chain), and ii) problem at the shifter which you can establish by again pulling at the freed cable at the rear mech while you shift into 6th/7th/8th etc. and see how much cable the shifter gives - it should be around 2.5mm per click for Shimano 9 speed.

 

[compo]

The most common cause I have found when shifting big to small sprockets becomes erratic is the final loop of cable housing to the rear mech. It becomes crudded up inside. I now just replace it as long as there are no other obvious causes such as frayed cables etc.

 

[BigonaBianchi]

Let's say there are 9 gears and 9th is highest (i.e. smallest rear sprocket).

If what you are saying is the rear mech/chain go straight to 9th when you shift from 5th into 6th, then likelihood is your shifter is faulty and slipping, which depending on what it is may or may not be repairable.

On the other hand if nothing happens when you shift from 5th to 6th to 7th to 8th etc. but it eventually goes straight from 5th to 9th, then the likeliest cause is sticky cabling system, but if not that (which seems you have established to be the case by now) then two other possibilities are i) rear mech fault (which could be established by feeling whether it is sprung and smooth traversing across the sprockets when without the chain), and ii) problem at the shifter which you can establish by again pulling at the freed cable at the rear mech while you shift into 6th/7th/8th etc. and see how much cable the shifter gives - it should be around 2.5mm per click for Shimano 9 speed.

Thanks. Yes it switched ok from the big cog to cog five...then.jumps right down to the smallest cog. Switching back from smallest to biggest cog it shifts fine across all of the 9 cogs.
Looking inside the shifter there is crud..Some time back I did put lube in the shifter..

 

[BigonaBianchi]

..starting to think i should take the shifter apart clean it and re assemble...been here before...easier said than done, even with a campag video guide...

 

[actonblue]

Is there play in the derailleur body? How is the guide pulley is it showing signs of wear?
These might not be the causes but should be considered to try and sort your problem.

 

[BigonaBianchi]

I had another look at the shifter...its all a bit to complex in there for me right now so Ive left it at the LBS...they took a quick look and seemedto think its a shifter fault..hope its repairable as the last one wasnt cheap...