I've recently purchased a second hand Orbea with a 105 groupset, and I've noticed the chain makes a rubbing-like noise when in the big front ring.
It's not rubbing anywhere though - the gears are perfectly indexed, both at the front and rear, and the limits are set correctly on both. Gear shifting is perfect, both on the way up and the way down, on both front and rear derailleurs.
I'm not sure of the history of the bicycle, nor how many miles it's done, but my first task was to degrease the chain and cassette and lubricate everything back up again - so it's very well lubricated and free of any dirt and grime - but no amount of lubricant makes this noise go away.
- The noise disappears when in the smaller front chain ring, specifically when the rear derailleur puts the chain under less tension. The chain is practically silent.
- When in the larger front chain ring, the rear derailleur puts the chain under more tension and the noise appears.
- If I keep it in the large front chain ring but take the tension out of the chain by moving rear derailleur by hand, the noise disappears.
Does anyone know what might be causing this?