Gears..

[Stantheman]

I can adjust my rear derailleur and get the gears running perfectly, but after a few miles they start to play up. Not indexing correctly and a bit rough on some of the changes. I have lubed the pivot points and greased the cable and its starting to do my nut in. No big deal really but just annoying. Any one got any tips.

 

[Nigeyy]

That's a bit strange. I can think of some things:
i. you have water/gunk in the cables that partially freeze or thicken up based on the temperatures you cycle in (my brake discs did this to me once on an off road ride where I didn't know I had a bit of water in the housing -froze solid, and no matter how hard I pulled the lever, it was stuck solid. When that happened -obviously at the point where I needed to brake -it was....err... interesting).
ii. the cable is lengthening/shortening due to the temperature (can't say I've had that happen, but may be a possibility, dunno, probably reaching with that)
iii. you are getting mud and dirt into the gears and cables and housing?
iv. the cable run is effected by turning the handlebars (obviously this one would only work if you were turning the handlebars when you were trying to change gear). Similarly, your cable is being pulled out of a stop (you should notice that though)
v. your shifters are not returning the cable length properly (i.e. they are a bit gummy causing the cable not to be released properly)
vi. all or some of the drivechain is a bit worn and putting your weight down on the pedals then amplifies that rather than when you test gear shifts on a stand.

Anyone else? I'm sure I'll have missed something!

 

[RecordAceFromNew]

Any one got any tips.

The most likely culprit is cabling. You can use a little known trick of the trade to investigate - shift into the lowest gear (largest sprocket at the back) normally, then without turning either wheel or crank click the rear shifter into the highest gear - the result is that since the rear mech remain trapped by the chain close to the largest sprocket, the gear cable will become slack, allowing you to ease the housings off the cable stops effortlessly without needing to release the inner cable from the rear mech - quick and handy huh?

At this point by sloshing the housings along the gear inner cable, you can feel for any friction, look for broken strand, kink, rust or gunge, allowing you to decide whether you need to clean/lubricate/replace inner wire and/or housing as appropriate. In your case, if I were you I would also pull one or more of the ferrules off to check and be sure the housings that have been used are truly gear cable housing with multiple inline strands, not brake cable housing with a single spiral wire - the misuse of the latter is unfortunately not uncommon due to numpty/unscrupulous shops/mechanics... The visual difference is shown below.

Another benefit of easing the ferrules off the housings is that it will allow you to examine whether they have been fitted correctly - housings should be cut clean and square to fit snuggly into correctly sized ferrules - ill fitting ferrule is another possible cause for unstable indexing.

 

[smokeysmoo]

+1 for a cabling culprit, but out of interest what gears are they?

 

[Stantheman]

It's a Shimano Alivio derailleur. I will have a closer look at the cable and shifters tomorrow.

 

[Svendo]

What RecordAce... said, although I've found that when using the slack cable trick it can sometimes be hard to detect friction that is causing problems when the system is under tension. The other thing to check is that the cable is tightly secured at the dérailleur and not slipping a bit when changing down, I've managed to do that in the past.
If you've got all the ferrules etc. cables and housing can be reasonably cheap. PBK do OEM shimano SP41 gear cable by the metre, other brands are also avaiable and can be much cheaper.