Gear indexing perfectly except for the lowest gear

[Fifelad]

I have recently replaced my rear gear cable, and the indexing is perfect, except that the lowest gear even though the chain shifts on to the biggest cog no bother, there is a noise where the chain appears to be not sitting dead right on the jockey wheels. Any ideas ?

 

[mrandmrspoves]

If you made absolutely no other changes to your set up then it is most likely that the gear cable tension needs a tiny tweak to either loosen it or tighten it.
If your gears (derailleur) are quicker going up onto the larger cogs than they are coming down onto the smaller cogs, loosen very slightly. If your gears are quicker going to a smallet cog than to a bigger cog, tighten slightly. Just use the barrel adjuster at the derailleur or in-line adjuster and just rotate by small amounts and gauge if it is improving or making it worse.

 

[Fifelad]

If you made absolutely no other changes to your set up then it is most likely that the gear cable tension needs a tiny tweak to either loosen it or tighten it.
If your gears (derailleur) are quicker going up onto the larger cogs than they are coming down onto the smaller cogs, loosen very slightly. If your gears are quicker going to a smallet cog than to a bigger cog, tighten slightly. Just use the barrel adjuster at the derailleur or in-line adjuster and just rotate by small amounts and gauge if it is improving or making it worse.

Sounds about right, I did start to tighten a bit more, but I was loathed to go too far and compromise the rest of the set up for the sake of one gear, but I can’t think it would be much else..🤔

 

[marzjennings]

Could be the upper limiter screw needs half a turn counter-clockwise. The screw stops the chain leaping over the lowest gear into the spokes, and sometimes if it's hair too tight it'll stop the chain seating cleaning on the lowest gear. Try a micro adjust or two and see if noise goes away.

 

[mickle]

This sounds like a job for a quarter turn of the limit screw. But before you do that you should check that your derailleur and hanger are straight & square and that your 'b' screw adjustment is allowing the top jockey to closely follow the profile of the cassette as it moves through its range (check it it every chain ring).

 

[Spiderweb]

Surely if the lowest gear was fine pre new cable then the limit screw was fine before and should be fine now?
In my experience limit screws never move on their own. Got to be a small tweak to the barrel adjuster that is required.

 

[Fifelad]

Back in from a chilly shed fettling; adjustment of the B screw has eliminated the clanking noise when in the lowest gear. Which begs the question, the only previous time I have adjusted the B screw was when I changed cassettes from an 11-28 to an 11-32 and I have been running with an 11-32 for some time. There has been no need to tinker with it previously. Some things are a mystery..🤔 Thanks for all your input folks.