Rear derailleur gear cable - Clean, oil, replace?

[CyclingBlob]

I've only had my bike (Carrera Subway 2) a month or 2, bought from new and while it was fine at first, the gears have become a little temperamental. I've had a go at re-indexing, adjusting limit screws, etc..

I've search these forums and watched all the obvious videos and am confident I've gone through the correct procedures for setting the rear derailleur up. It's fairly simple so I'm not asking for help with that side of things. The barrel adjuster was already set at it's tightest so I couldn't loosen it off to help with setting things up, so I loosened the cable and basically started from scratch. I've now got it back to how it was before, with troublesome shifting.

The problem is that when setting the barrel adjuster, either the high gears will be fine or the low gears will be. I can't set it to have both shifting correctly. I've looked into possible reasons and the general consensus is that either the derailleur is bent, or the cable is sticking.

From what I can see with my eye, the derailleur appears to be perpendicular and I haven't had any knocks on that side of the bike, so I don't think that's the cause.

So I'm left with the cable. I've read here that 90% of the time, the cable is the issue. I've checked the routing and while I don't particularly like how it's so exposed and tightly rubs against the frame on some of it's route, it is fitted correctly so I guess that's just how it is.

As it's almost brand new, I can't believe the cable is stretched or the shifter worn, so I'll take those out of the equation. The problem I had started occurring slowly, where I'd be riding and 1 or 2 gears were noisy, or I couldn't engage one of them. It seemed to get worse with time, but I'm talking about very low mileage here so I'd be surprised if the cable already needs cleaning. Maybe though? I've not been in mud or anything, just some rain once.

So after all that waffle, which I wrote so you know details of the problem, my question is - How likely is it that removing, cleaning or oiling the cable is going to fix this? Is there some sort of trick to definitely prove the cable is the problem? Is it worth replacing it even though it's almost new, with something better? I basically hope to hear from others with Carrera bikes and similar gearing to see what their experience is. I'm happy to replace the cable inner and outers IF that's likely to fix it, but I can't afford to throw money at it without being sure, I'm already broke enough.

Maybe a temporary fix for now, with a view to change the cable if it proves to be sensible to prevent the same issue again. Should I spray something like GT85 on it, maybe where it rubs against the frame? Any other suggestions would be appreciated. Thanks!

[francovendee]

Normally the first thing to look at is the inner cables when you start to get shifting problems. Unless the bike has been in really dirty conditions then a new bike shouldn't need new cables.
Have you checked that cables haven't been trapped in some way or the shifter/ derailleur hasn't been damaged?
Cleaning and oiling the cable would be something quick and easy to do. Try it, it won't do any harm and might cure the problems.

[531colin]

Put the bike in bottom gear, then put the shifter in top gear.....this makes the cable very slack.
Pull the cable out of all the slotted cable guides, slide the outer down the cable, oil the cable and slide the outer back.
Also oil the cable where it goes over the bottom bracket cable guide.
Most likely there is a bit of corrosion in the last loop of outer cable down by the rear mech.......often looks white.
A drop of oil every so often keeps things sweet.

[rareposter]

As it's almost brand new, I can't believe the cable is stretched or the shifter worn, so I'll take those out of the equation.

Nope, that's exactly what the issue is.
Most bike shops offer a free first service within the first 6 weeks or so precisely because everything "wears in" a bit, cables stretch etc.

If you've ever played any stringed instrument, the first week or two after fitting new strings, the thing needs constant tuning as the strings stretch and bed in. Same here.

You've massively overcomplicated a very simple adjustment - it should be no more than a couple of tweaks of the barrel adjuster. However now that you've started loosening cables, it'll mean setting the gears up from scratch. There are plenty of videos online of how to do this, but really the bike needs to go back to the shop you bought it from for the free first service.

[CyclingBlob]

Normally the first thing to look at is the inner cables when you start to get shifting problems. Unless the bike has been in really dirty conditions then a new bike shouldn't need new cables.
Have you checked that cables haven't been trapped in some way or the shifter/ derailleur hasn't been damaged?
Cleaning and oiling the cable would be something quick and easy to do. Try it, it won't do any harm and might cure the problems.

Thanks for replying. It's only been in rain once, no mud, just some deep puddles but so little and it's all so new, I'd be surprised if that's the problem. Something has to be wrong though.

I have checked the full length of the cable and it does seem fine, other than how tightly it attaches to the lower part of the frame, but I know that's where it's supposed to be. Seems a poor design to me but I guess it's normal. The shifter and derailleur don't appear damaged to my eye. It all looks straight, moves freely by hand, etc..

I'll do as you suggest and clean/oil the cable. You're right, it won't do harm and I'm out of options otherwise.

[CyclingBlob]

Put the bike in bottom gear, then put the shifter in top gear.....this makes the cable very slack.
Pull the cable out of all the slotted cable guides, slide the outer down the cable, oil the cable and slide the outer back.
Also oil the cable where it goes over the bottom bracket cable guide.
Most likely there is a bit of corrosion in the last loop of outer cable down by the rear mech.......often looks white.
A drop of oil every so often keeps things sweet.

I'll do that later today, thank you for the detailed instructions, it's very helpful.

[CyclingBlob]

As it's almost brand new, I can't believe the cable is stretched or the shifter worn, so I'll take those out of the equation.

Nope, that's exactly what the issue is.
Most bike shops offer a free first service within the first 6 weeks or so precisely because everything "wears in" a bit, cables stretch etc.

If you've ever played any stringed instrument, the first week or two after fitting new strings, the thing needs constant tuning as the strings stretch and bed in. Same here.

You've massively overcomplicated a very simple adjustment - it should be no more than a couple of tweaks of the barrel adjuster. However now that you've started loosening cables, it'll mean setting the gears up from scratch. There are plenty of videos online of how to do this, but really the bike needs to go back to the shop you bought it from for the free first service.

I'd rather not take it back to Halfords, it shouldn't be required for a basic thing and they'll only do what I can do. I'm trying to learn how to maintain the bike myself, and so far with what I did yesterday I've learned quite a lot about how the gears work, which will help in future.

I agree that new cables can stretch, you're right to compare them to stringed instruments (which I have experience of). I hadn't thought of it like that before. However, the problem isn't just a possible stretched cable. I don't agree that I've overcomplicated things, as the fact is that simply adjusting the barrel adjuster did not solve the problem. I may not have set things up before myself but it's a very simple thing to do when you know how, so I'm confident I've set things up exactly as they should be. There is an extra problem that is no better or worse since I re-set things, so it is looking likely to be the cable sticking.

Thanks for your thoughts.

[Jdsk]

As it's almost brand new, I can't believe the cable is stretched or the shifter worn, so I'll take those out of the equation.

Nope, that's exactly what the issue is.
Most bike shops offer a free first service within the first 6 weeks or so precisely because everything "wears in" a bit, cables stretch etc.

If you've ever played any stringed instrument, the first week or two after fitting new strings, the thing needs constant tuning as the strings stretch and bed in. Same here.

You've massively overcomplicated a very simple adjustment - it should be no more than a couple of tweaks of the barrel adjuster. However now that you've started loosening cables, it'll mean setting the gears up from scratch. There are plenty of videos online of how to do this, but really the bike needs to go back to the shop you bought it from for the free first service.

I'd rather not take it back to Halfords, it shouldn't be required for a basic thing and they'll only do what I can do. I'm trying to learn how to maintain the bike myself, and so far with what I did yesterday I've learned quite a lot about how the gears work, which will help in future.
...

Congratulations on deciding to learn how to DIY.

I don't recommend using YouTube videos from unknown sources for this. If they don't quite match your kit or your task they can be very misleading.

There are two renowned sources where that is much less of a problem:

Sheldon Brown:
https://www.sheldonbrown.com/bicycleGears.html
https://www.sheldonbrown.com

Park Tools Repair Help:
https://www.parktool.com/en-us/blog/rep ... derailleur
https://www.parktool.com/en-us/blog/repair-help

Jonathan

[rotavator]

The problem is that when setting the barrel adjuster, either the high gears will be fine or the low gears will be. I can't set it to have both shifting correctly. I've looked into possible reasons and the general consensus is that either the derailleur is bent, or the cable is sticking.

Assuming that you have 9 speed Shimano rear gears...

I had exactly this problem with two of my bikes. No matter what I tried I could not get the full range of gears to index correctly. Following advice on this forum (sorry I can't find the thread despite a quick search), I bought and fitted SRAM X5 rear derailers and thumb shifters and I have not had any trouble since. Apparently SRAM's 1:1 actuation ratio is the key difference to Shimano's set up.

[cycleruk]

From what I can see with my eye, the derailleur appears to be perpendicular and I haven't had any knocks on that side of the bike, so I don't think that's the cause.

Besides perpendicular, check that is not twisted. Put the chain in small too small and look down from above. The derailleur cage should be parallel to the sprockets.

If you feel confident enough then I would strip the cable and check for any kinks in the wire.
Make sure the outers run smooth when sliding them up and down on the inner.
Check, clean and reassemble.
Any tight bends ?
Damp roads can very quickly introduce dirt and grime onto cables especially under the bottom bracket.

[AndyK]

The problem is that when setting the barrel adjuster, either the high gears will be fine or the low gears will be. I can't set it to have both shifting correctly. I've looked into possible reasons and the general consensus is that either the derailleur is bent, or the cable is sticking.

I think a lot of the replies have overlooked this key point. It sounds like the classic symptom of a bent derailleur hanger - the part that connects the derailleur to the frame.

A bent derailleur would give similar symptoms, but the hanger is there as a sacrificial part to protect the more expensive parts (frame and derailleur) from damage on impact, so the hanger is more likely. I know you say you haven't had any knocks, but this is the kind of thing that can happen while you weren't looking: you lean your bike somewhere, someone else accidentally knocks it over and hurriedly props it back up again.

So. Ideally you would use a derailleur hanger alignment gauge to check the hanger, but they're relatively expensive tools. You can try to do it by eye: start by removing the derailleur itself, then use a ruler or similar to work out whether the hanger is straight. If it's only slightly out you should be able to bend it back using an adjustable spanner, but there is a risk it will crack. There are various how-to's knocking around online.

Alternatively just buy a new derailleur hanger for £10 from Halfords, swap it with the existing one and see if it makes a difference. If it fixes the problem, job done! If it doesn't, at least you now have a spare hanger stashed away for that day when the original one does get bent.

The hangers vary a lot in design, even changing year-to-year on the same model of bike. so I recommend going into Halfords and asking for the hanger for your specific bike. That way if you get sold the wrong one it's their fault.

[Eyebrox]

Take it back to Halfords for its initial free service despite your keenness to DIY. Talk to the staff afterwards and that will guide you next time. It could be any one of the above problems or a combination of them. Halfords don't always get a good name for servicing but they know Carreras inside out as the sole dealers of the brand.

[CyclingBlob]

Congratulations on deciding to learn how to DIY.

I don't recommend using YouTube videos from unknown sources for this. If they don't quite match your kit or your task they can be very misleading.

There are two renowned sources where that is much less of a problem:

Sheldon Brown:
https://www.sheldonbrown.com/bicycleGears.html
https://www.sheldonbrown.com

Park Tools Repair Help:
https://www.parktool.com/en-us/blog/rep ... derailleur
https://www.parktool.com/en-us/blog/repair-help

Jonathan

Thanks for that Jonathan. I've watched several videos from Park, which are all done very well and I followed along with one of them to help me with gear indexing. I also saw that other link you gave in a previous thread, which is also helpful. Thank you!

[CyclingBlob]

Assuming that you have 9 speed Shimano rear gears...

I had exactly this problem with two of my bikes. No matter what I tried I could not get the full range of gears to index correctly. Following advice on this forum (sorry I can't find the thread despite a quick search), I bought and fitted SRAM X5 rear derailers and thumb shifters and I have not had any trouble since. Apparently SRAM's 1:1 actuation ratio is the key difference to Shimano's set up.

I intended to say that in my first post - Yes it is the 9 speed Shimano I have.

Well that's interesting that you've had it on 2 bikes. Did you try all the stuff mentioned here already such as cleaning/degreasing the cable, making sure there were no kinks, etc.? I'm guessing so as you said "no matter what I tried".

I'll do a search for the thread you mentioned later. I've just been working on the bike and will update after finishing these replies.

[CyclingBlob]

If you feel confident enough then I would strip the cable and check for any kinks in the wire.
Make sure the outers run smooth when sliding them up and down on the inner.
Check, clean and reassemble.
Any tight bends ?
Damp roads can very quickly introduce dirt and grime onto cables especially under the bottom bracket.

I've just come back from doing that. The cable didn't seem dirty but I took it off, cleaned the whole thing, squirted some GT85 up the outers too, ran the cable by hand back and forth. I checked for kinks and it's all running freely.

The result is exactly the same problem. There is one clue still and I'll upload a video soon to show it.