New Chain on 12 speed shimano - thrumming?!...

[edruid]

Swapped out at just over 50% wear.

Shifting worked fine.

But now there is a constant thrum, no matter how I adjust the tensioner

And the chain now keeps slipping off the front ring (not great when you're in Snowdonia).

Lubed the new chain before use.

Definitely same link count

Not had this before, anyone got any theories?

Thanks

edruid

 

[theremotejuggernaut]

Have you routed it around the rear mech correctly? There's a little tab between the pulleys, the chain has to be on the correct side otherwise it rubs.

Have you got the chain the right way around? Writing on the outside?

 

[irie]

Have you routed it around the rear mech correctly? There's a little tab between the pulleys, the chain has to be on the correct side otherwise it rubs.

Have done that myself.

 

[theremotejuggernaut]

Have done that myself.

Me too. And the chain being the wrong way round. And I still do both, despite knowing not to

 

[edruid]

Have you routed it around the rear mech correctly? There's a little tab between the pulleys, the chain has to be on the correct side otherwise it rubs.

Have you got the chain the right way around? Writing on the outside?

Thanks, would love it to be either of those easily correctable mistakes (which I have made before) but sadly not this time . . .

 

[theremotejuggernaut]

Does the chain mesh properly with the chainring? Could be a worn chainring being unhappy with a new chain?

 

[edruid]

Does the chain mesh properly with the chainring? Could be a worn chainring being unhappy with a new chain?

Is what i fear (££). How can i tell?

 

[theremotejuggernaut]

If it meshes properly, there will be no gaps between the chain and the chainring. The links will fit perfectly between the teeth (also, narrow/wide links need to be aligned with the narrow/wide teeth).

I'd flip the bike over and pedal it slowly looking at the chainring, if it looks like the chain is climbing out of the gaps between the teeth then the chainring is worn.

Also, if the chainring is worn, it can sometimes hold onto the chain as the chain moves around the bottom of the chainring. Look at the bottom of the ring where the chain starts heading back towards the derailleur. The chain should slide cleanly off the chainring. If it looks like the chainring is dragging the chain around, then it's another sign that it's worn.

Same applies to the cassette. The chain should sit nicely between the teeth.

 

[edruid]

If it meshes properly, there will be no gaps between the chain and the chainring. The links will fit perfectly between the teeth (also, narrow/wide links need to be aligned with the narrow/wide teeth).

I'd flip the bike over and pedal it slowly looking at the chainring, if it looks like the chain is climbing out of the gaps between the teeth then the chainring is worn.

Also, if the chainring is worn, it can sometimes hold onto the chain as the chain moves around the bottom of the chainring. Look at the bottom of the ring where the chain starts heading back towards the derailleur. The chain should slide cleanly off the chainring. If it looks like the chainring is dragging the chain around, then it's another sign that it's worn.

Same applies to the cassette. The chain should sit nicely between the teeth.

Thanks dude

 

[theremotejuggernaut]

Did you sort it?

 

[kevtp19]

Is what i fear (££). How can i tell?

Mine did this, but after a few rides it wore on ok. Probably be the last time we get away with it before needing to replace all the drive train.

 

[Stihldog]

Quick Link? If you’re installing a new chain install a new quick link also. Usually one is provided with a new chain. …and these can be installed incorrectly.

A Shimano link for a Shimano chain. Direction of chain travel is important. That’s usually indicated by a small arrow. Insure that both sides of the quick link are “snapped” into place. That can happen and may cause problems while the chain travels around the chainring. ( if one side is not clipped properly ).

Besides the narrow/wide issue …chain suck can happen on an old or worn chainring.

But carefully check the quick link. They can sometimes be reused but a new and properly clipped link is important.

 

[Shorty4]

I had similar a few times now and it was the chainring every time, new chainring and it all works ok. I use alloy chainrings so the do wear quicker than a steel one but are not that expensive.
Its on a Focus Jam2 C Plus of 2018 vintage with Shimano 8000, still going strong at just under 10k kms