Rumbling noise from new cassette

[San Marco]

Hi all

Wondering if I could get some help. I replaced my Shimano 8 speed cassette (11-28) with another HG-50 8-speed but with a different teeth combination (13-26). After fitting it I could hear and feel a rumbling noise around the rear derailleur area. I went for a ride round the block and the noise and how the trembling felt through the frame was even worse. I thought it had to do with cable tension but this was ok, I tweaked a bit but made no difference. I then thought I may have over-thightened the cassette, so I removed the wheel, unlocked the cassette, checked all sprockets were ok, and fitted again a bit more loose this time. Things remained the same, the rumbling noise was still there. The chain looks centred in between the sprockets. What can this be??

thanks

 

[uclown2002]

I suspect the old chain with new cassette is the problem. Try new chain.

 

[potsy]

May need to adjust the b screw now you have a smaller cassette, may also need to shorten the chain a link.

 

[jowwy]

Did you put the spacer back in or didnt it have one

 

[San Marco]

@jowwy no, there wasn't a spacer in the box that contained the new cassette. Don't remember seeing one with the old one, but will have a look. I guess if a spacer was needed it would be supplied with the cassette itself?

I'm starting to think is due to chain length as suggested above, as the rumbling noise does seem to get louder the smaller the sproket at the back....

 

[HLaB]

If its happening in all gears I'd bet the chain is run the wrong side of the jockey wheel retainers (don't ask me how I know )

If its only happening when you are in your wee ring at the front your chain as suggested might be too long and need shortened, you may also need to adjust your b screw to bring the cage closer to the cassette when in the biggest cog (lowest gear).

 

[San Marco]

@HLaB Thanks for your suggestion. Yes, the noise does happen in all the gears, whether using the 50 or 34 chainring at the front. The noise does seemsto come from the deraileur/jockey wheel area. Is there a way to fix it ?
Thanks again.

 

[HLaB]

@HLaB Thanks for your suggestion. Yes, the noise does happen in all the gears, whether using the 50 or 34 chainring at the front. The noise does seemsto come from the deraileur/jockey wheel area. Is there a way to fix it ?
Thanks again.

You could check that the chain is threaded through all parts of the jockey cage properly, google will probably throw up a goos image you can compare to. If it isn't you'll need to break the chain, thread it correctly and rejoin. If thats the case I'd reccomend rejoining with a quick link like KMC do, it faster (easier to get right first time) and avoids a weak joint.