The dreaded indexing of gears…

I’ve got this odd problem. New chain. New cassette. Fitted them. Went to fine tune…

When I shift up, all is good. Mech aligns nicely with each cog, no rattles, smooth changes and smooth running all the way.

When down shifting though, it’s as if it’s moving half a shift more. Fine through the low gears, but by the time it reaches the smaller cogs the mech is clearly way out of alignment, chains starting to rattle, and it just skips the 2nd from bottom cog entirely because it’s that far out.

Pretty sure it did the same on the old cassette and chain.

How can it shift up perfectly, but not down?

Bad setup? Bad mech? Bent hanger (looks relatively straight to the eye)?

Mech is Shimano Sora and done just short of 10k miles.

Are the cables running freely ?

Cables were replaced about 6 months ago, so in good condition. Haven’t had them off the mech, but they appear to be clean and moving OK.

Mech is Shimano Sora and done just short of 10k miles.

That is a lot of miles (10k=10 000). Mech is probably worn beyond use hence the up shifts ok but the down not since the mech can “open” more than expected due to wear. I’m surprised it does not try to shift back half a gear when you shift up. .

Yeah, I was wondering if maybe the spring is worn or something.

I seem to have it working a little better now and hitting all the cogs both ways, but with the caveat that I have to give it a little extra squeeze to shift up, rather than shifting on the click.

Def wear then. I have that in my knackered derailleurs. It is the pins/ bushes that are worn, the spring will be slightly slack but it is new derailleur time.

Hmmm, they don’t cost much to be fair. About the price of a chain! Had a go on it today and it’s not too bad out on the road tbh. Will see how it gets on.

10,000 miles! Blimey