My new Bizango is settling down nicely, the forks are even starting to feel like they work (a bit) but the noise from the chain is driving me mad!!!!

It’s only in the two largest sprockets, in the middle ring. Chain isn’t rubbing on the front mech. Its much worse under load, but when pedaling very slowly, it feels like the pedal bearings are knackered, but in the granny ring or further down the cassette the feeling/noise goes away.

Any ideas? Something is obviously not right, it didn’t make this noise when it was new, but I don’t think it’s chain stretch as the indexing is fine and shifting smoothly.

The bike has sliding dropouts, I’ve checked these are straight and tight, and I’ve even tried sliding the whole lot forward, which has helped but not cure the problem (backwards was worse).

Cheers in advance

This might sound crazy but have you checked the spoke tensions ? I had something similar i.e. odd noises from the cassette in large rear sprockets. Turned out to be loose spokes in the rear wheel, perhaps this led to a slight flex in the rear hub and so caused the noise.

Cross chaining

I don’t think it could be cross chaining, middle ring big sprocket shouldn’t be that noisy on a 9 speed set up. If it was big ring I’d agree, but even then it’s not normally this noisy, and fine on my other bike.

I’ll check the spokes too but the wheel is straight.

Have you got enough tension on the B screw?
Top jockey wheel might be clashing with the sprockets.

^^ would be my first guess as well

It looked ok in the stand, but the noise only occurs under load (climbing/sprinting/wheelying with a 3 sheeter in one hand to impress the local burdz)