Noisy new chain

Question

I ride a mountain bike with SRAM XX1 running gear. I changed the 11 speed SRAM chain for a 11 speed KMC chain. The new chain is noisy. It sounds as if it is grinding against something but I cannot see anything at all that could be doing this.

Changed it back to old chain - no problem. Changed it to new chain - grinding again.

Is it the just the KMC brand that could be doing this?

Answer 1

It's not the chain but rather new chain/old drivetrain combination. Depending on how worn your chainring/cassette are, the noise may be temporary or permanent.

If cogs of your drivetrain are heavily worn, it means that links of the new chain will never lie precisely on them, causing invisible but noisy movements as the chain attempts to position itself on the chainring's teeth (but it fails). In this case, your options are:

1. to replace chainring and possibly cassette so that all parts of the drivetrain are new and match each other;
2. flip the chainring so that another side of its teeth which are less worn is used. This will not help if sound comes from the cassette, but I'd bet it is the chainring because cassette's wear is distributed more between its gears.
3. Get back the old chain on and use it until your are ready to go with the option number 1.

If the chainring/cassette are only moderately worn, you could try to wait until the new chain wears a little. Then the unpleasant sound may go away. This, and flipping the chainring, helped me on my singlespeed. Oiling the new chain more than one would regularly do may give a short relief but in general it will not help in the long term. In any case, no guarantee when the noise disappears.

To understand how worn your drivetrain is, measure your old chain's length relative to a new one. There are cheap devices available for that. An increase of 0.5% (for an 11-speed chain) means it is heavily worn, and so is the rest of the drivetrain. 0.25% or less means moderate wear.