Worn cassette / chain slip

[ipcookson]

Hi all, I recently changed my bottom bracket and at the same time changed my chain as it was quite badly worn, also cleaned the rear derailleur jockeys. I've tried to keep on top of drivetrain cleanliness and chain wear to prolong the life of rear cassettes and thought the current one looked ok, but after changing the chain got some chain slip in the lowest gears. Attached is a pic of the cassette, which to me doesn't look too bad, but I've bought another just in case. Only other thing of note is that the new bottom bracket I had fitted was 118mm whereas the original was 115mm.

Any thoughts?

[Mick F]

If your chain was badly worn, it will have damaged the smaller sprockets and/or the most used sprockets too.
That is your problem.

You need a complete new cassette, or at least to renew the sprockets that are slipping.

From the symptoms you describe, the BB width won't be it.

[Brucey]

your picture is not super-clear but it looks like a cassette that has been used on a compact double, used roughly as intended, i.e. sprockets #2 and #3 look decidedly hooked. Any slightly hooked sprockets will probably skip under load when a new chain is fitted.

If you have fitted a slightly longer bottom bracket spindle it won't have improved the chainline when running big-big. The worse chainline likely won't cause skipping, but it isn't a great idea.

If you still have the old chain, check it for wear. My guess is that it will be worn about 1%; if so it means you left it that little bit too long before changing it.

cheers

[ipcookson]

Thanks Mick. Tried to put the new cassette on to see if that solves it, but now encountered another problem (can you tell I'm new to this)? The new cassette is a 9 speed Shimano compatible, the hubs I have are shimano RS something, and I didn't have a spacer on before but now I can't tighten the lockring on the new cassette!

[Brucey]

are you sure you have the last sprocket correctly fitted?

cheers

[ipcookson]

are you sure you have the last sprocket correctly fitted?

cheers

Yeah pretty sure. I think the whole cassette (a Decthlon own brand version) was marginally narrower than the Shimano one I had on. I went and got a 1mm spacer and it seems to have sorted it out. Thanks everyone. Really helpful forum.