sloppycoder

I'm trying to replace the very old and somewhat stretched chain on my MTB, spent ages looking for compatibility info and finally ordered a KMC X8.93. see below...

https://www.kmcchain.com/index.php?ln...mo=view&id=617

Have fitted this chain but now suffer phantom shifting/outright chain jumping in ALL gears at the rear end Cant adjust it out at all and its bad enough that you wouldn't even consider standing up (not that I really do or need to, just trying to convey how fluid it is!)

The other equipment is...

Shimano Acera rear mech (cant tell which one - sorry!)
Shimano CS HG 30-81 cassette
Shimano ST-EF 50-8r shifter

The chain that came off was a Shimano IG-31, I did try to get a direct replacement but it seems they are discontinued/out of stock everywhere? Also looked for a chain compatibility guide from Shimano or a general one but had no luck.

Any help much appreciated,

Alf

fietsbob

Go buy the rest of the drive train too, cassette wore into the old chain.
you too long on the chain replacement.

well biked

The cogs on your 8 speed cassette are worn out. You said the chain you replaced was somewhat worn, it's very common in that situation for the cassette to have enough wear on it that a new chain will not mesh properly with the teeth on the cogs. This causes skipping, chain jumping, basically an unrideable situation, as you describe. Replace the cassette with a new one and all will likely be well. Chainrings can wear out, too, but last m-u-c-h longer than cassettes.

larry_llama

Yep, you need a new cassette.. if you are lucky, your chainrings are still OK :-)

MudPie

Sheldon Brown discusses this in good detail, scroll down 3/4 of the page: https://sheldonbrown.com/chains.html

1. You can save the cassette if you replace the chain before it stretches too much.

2. 12 links should measure 12 inches, exactly, on a new chain.

2a) If 12 links measure 12-1/16", the cassette is probably not damaged and if you change the chain, it should play fine with the cassette.

2b) If 12 links measure 12-1/8", the cassette is probably damaged and you would need a new cassette (and chain).

However, cassettes don't last forever. If you follow 2a) above, you might get three or four chains before you need to replace the cassette.

MudPie

BTW. I recently switched to a KMC chain and so far, I prefer it over SRAM and Shimano chains. It seems to run quieter and shifts nicely. So far, almost 2000 miles on it and not a single hiccup with it. Plays nice with the Shimano chain rings and SRAM cassette.

sloppycoder

Thanks

Ill measure old chain in the morning and get a new cassette ordered if its fubar, i think your all probably right.

MudPie

It'd be "fun" to see how stretched it really is.

Report back when you measure.

You can buy "chain checkers", but they seem to give inaccurate results because of the way they measure. However, measuring with a good quality rule is the way to go.

sloppycoder

"MudPie
It'd be "fun" to see how stretched it really is."


*ahem* Twelve and a quarter (12 1/4")! oops...

Looking into a replacement cassette, i spotted that the current worn out one is an IG model which from that sheldon brown site will only work with IG chain? Since ive already bought a "normal" chain can i replace instead with a "normal" 8 speed cassette? If so any reccomendations?

Heres the relevant bit from sheldon's site https://sheldonbrown.com/gloss_i-k.html#ig


Guess i better take a good look at the chainrings too,

Ho- Hum, live and learn...

Thanks again for all the quick helpful replies!

Alf

sloppycoder

Anyone? I'm finding a lot of conflicting info! Only viable ish alternative seems to be an SRAM one but that has some claims about needing its own special type of chain too

cycle_maven

Just get a Hyperglide cassette and all will be well... I don't think you can even find IG cassettes anymore. Anyway, your old cassette is an HG variety, so your new one should be as well. Here's one, an HG30 11-32: https://www.niagaracycle.com/product_...oducts_id=6609 For 13 bux you can't go wrong...