I noticed the chain and cassette were getting pretty worn, certainly the chain was ‘stretching’. The chainset and rings are less than 7 months old, but I’ve ridden it through the winter. I swapped the chain and cassette from my CX bike which hasnt seen much use.

A strange audible ‘rumble’is coming from the transmission. I’m wondering if it could be the pulley wheels on the rear XO mech.

Am I barking up the wrong tree or should I give it a while to bed in?

XO pulley wheels, where?

The rings are probably slightly worn and the rumble is the chain not meshing properly with the rings.

could be either, shouldn’t be tough to diagnose

Have you changed to a different size of cassette? It could be that the top jocket is catching the spocket. Try a couple of turns on the B-tension screw.

I swapped a Sram cassette for an XT one, so I may try that. I never thought to count the teeth.

I was in chainring wear denial. The middle ring was fairly worn. FSA chainrings must be made of cheese. Swapped middle and wee ring for some Middleburns pinched from my VT. Rumble gone.

Is anyone else a serial skimper?, trying to eek out the last bit of life from their bikes and bits.

I never skimp on my cereal.