I recently got a Tacx Flux 2 Smart trainer (because lockdown) and decided to get a new cassette and chain as well, since I won't be doing any riding anytime soon and would like to keep everything nice and clean in the house.
I installed the cassette on the trainer,checked I was using the right adapters for cassette and QR, and then measured the new chain against the old one (they are the same KMC 9 speed), making sure they were exactly the same length. I then installed the chain with the supplied quick link, making sure it is routed the right way through the jockey wheels.
However, I now get a very clear droning, grinding noise and perceivable vibration when in the smaller 3 rings. The noise almost disappears when in lower gears. The shifting fine though, and I can get shift in all gears.
I have no idea what can be wrong and it feels almost like the chain has a hard time slotting into the teeth of the chain rings. Almost like the each roller slightly hits every tooth before grabbing on. If I had to describe it in an onomatopea, it would be a grindy "RRRrRrrrrrrRRrrrRrRrrrRr"
What could be the cause of this? Is it just because the chain and cassette both need to be bedded in? Is it lubrication?
** UPDATE ** I finally managed to ride the bike outside and cannot reproduce the same noise or vibration. It seems that the issue is with the bike one the trainer.