6 speed rear derailleur problems

[IBB98]

Hi folks, this is my very first post and I'm certainly no expert at cycling or bike maintenance so please forgive me for asking stupid questions. I'm not the most knowledgeable about bikes but I have just completed a degree in Mechanical Engineering and like to think I'm at least partly handy so should be able to do simple maintenance jobs myself hopefully.

Over the lockdown period and into Summer I decided I'd take out my old bike (probably approx. 15 years old, not well maintained) and go for a few cycles. I was planning on trying to get fitter and get more confident on a bike but I've ran into some problems.

My rear derailleur (an old six speed shimano sis) was resting against what I believe is called the chainstay, and when I tried to change gears it would get caught on the chainstay, making it impossible for it to physically change gears. Many YouTube videos and curse words later I managed to figure out what the problem was (it wasn't on properly, it needed to be against a sort of notch to hold it away), take off the derailleur and put it back on correctly so it is held away from the chainstay and not getting caught.

I was hopeful that that would be the end of it and all it would need was for me to index the gears but now I'm not so sure. While cycling I can easily go down the gears (the tension applied to the gear cable successfully moved the derailleur inwards towards the spoke and changes gears downwards) but when I attempt to move the gears back upwards nothing happens.

Is it possible that a professional indexing the gears could fix this? Or (as I believe) is the spring that's supposed to pull the derailleur back is worn and isn't up to it's job?

If the derailleur is indeed faulty, is there any specific details I need to look out for when replacing it, or will any Six Speed Shimano derailleur work? Does anybody have any recommendations? I'm not planning on going racing, I just want something simple and cost effective for me to fit and index myself that will take some abuse from my lack of cycling experience. Also, would it be worthwhile changing my gear cable if I do have to have the derailleur off anyway? Is that difficult to do? Any specific cables I need, are they expensive?

Thanks for your help guys,
Ian

 

[I like Skol]

Try oiling the cable, especially the last section where it turns to enter the derailiuer. Inspect the cable, it may well be rusty inside the outer casings, they often are on older, neglected bikes. As a short term fix you can polish up the steel inner with sandpaper (I know it isn't sand nowadays!) Then wipe it clean and oil it. 6spd gear systems are not so super sensitive to Uber accurate indexing so can tolerate less than optimal cables providing they can move smoothly.

 

[overmind]

Agreed, my guess would be gear cable. I would replace inner and outer cable to rear derailleur. 6 years is a lot of corrosion.

Watch some videos on youtube about how to do this. If you end up changing the cable you will also need a nipple for the cable end. You can get all the bits you need Decathlon, Halfords or any decent bike shop (also try Wilkinson which is very good value but better online).

Tip: To cut the outer cable keep the old bits and cut the new bit the same as the old.

If you have the confidence/guts to go ahead welcome to the rabbit hole that is bicycle maintenance. Soon you will be mickle'ing your chain and truing/dishing wheels.

 

[Cycleops]

As above, replace the cables. My local LBS guy reckons cables can start to go rusty after six months so you can imagine what yours must be like after fifteen years .Dont forget to grease the new one.

 

[raleighnut]

Ditto new cable time

 

[IBB98]

Thanks a million for all your help everybody, I'll try replacing the cables!

 

[I like Skol]

Thanks a million for all your help everybody, I'll try replacing the cables!

I wouldn't, not until I knew they were the problem. You can throw parts at it if you like but a better approach would be to identity the fault first.

 

[rrarider]

Completely slacken the cable to the mechanism by undoing the pinch bolt which attaches the cable to the mech. The derailleur should then move outwards to the smallest sprocket on the freewheel or freehub. This would test that the spring was OK and that the mechanism itself doesn't require oiling.

 

[PpPete]

You can throw parts at it if you like but a better approach would be to identity the fault first.

Whilst a cable problem is the most likely issue from the symptoms described it's always better to be 100% sure of identifying the true problem first. DAMHIKT !

Completely slacken the cable to the mechanism by undoing the pinch bolt which attaches the cable to the mech. The derailleur should then move outwards to the smallest sprocket on the freewheel or freehub. This would test that the spring was OK and that the mechanism itself doesn't require oiling.

Assuming the derailleur does move freely back outwards, the next thing to check is certainly the cable: how freely does the inner steel bit move in the outer? you can test it whilst it's disconnected, a modern stainless cable in teflon lined outer has a bugger-all friction. A fifteen year old galvanised cable in a rusty outer? can be more than the spring in the rear derailleur will pull against.