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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?

  • 3
    It sounds to me like the chain and/or chainring is worn. And possibly the rear cluster as well. – Daniel R Hicks Jun 29 '17 at 21:33
  • Can you tell where the noise is coming from? The biggest noise from chain stretch will come from the teeth on the chainring or cog itself. If you're not familiar, you can measure chain stretch. Also, check your chainrings for (differing) wear: an excellent picture is in this question, which shows little wear on the small ring, medium wear on the large ring, and extreme wear on the middle ring. – hoc_age Jun 30 '17 at 0:48
  • Jockey wheels can also do strange things when worn. Could be worth an inspection because they are directly affected by chain tension - they tension the lower part of the chain. In theory your pedal pressure tensions the top part of the chain, so that should be noticeable under pressure in any gear. – Criggie Jun 30 '17 at 0:55
  • Another testing step. Ride in a gear that makes the noise. Stop without changing gear. Lean it against something or put it on a sturdy stand with a strap holding the back brake on, then lean hard on the pedals (alternately) by hand, flick the rear derailleur etc. Check clearances and look for odd behaviour in the rear derailleur. This is a way to replicate the way some things some things sit differently under real tension – Chris H Jun 30 '17 at 6:38
  • Unfortunately I can't tell where the noise is coming from exactly. It could be the cassette, or it could be the jockey wheels. It's definitely somewhere near the rear derailleur. I've just replaced the chain, but if anything the noise has got a little bit worse. Checking the cassette some of the teeth do appear worn so I'm going to try that next. – pcdj Jun 30 '17 at 12:36
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Hard to diagnose without visual access to the bike, but in my experience, some causes of such noise can be misalignment of the rear deraileur - possibly caused by a bent hanger. Watch this Park Tool video on rear deraileur hanger alignment: http://www.parktool.com/blog/repair-help/rear-derailleur-hanger-alignment

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Here is a suggestion that might help with your troubleshooting.

It might be the b-tension screw that needs to be adjusted. If you say the noise appears under tension, check if the g-pulley (upper pulley) on your derailleur is somehow rubbing the largest gears in the back the wrong way :)

Here's a video tutorial on adjusting the b-tension screw.

Another suggestion that comes to my mind is that the derailleur arm could possibly give under tension and bend to the right or to the left, causing the shifting to be imprecise and rubbing the sprockets. This could happen because of a to short chain or bad derailleur (having play). This one is also easy to check, by looking at the rear sprockets when the noise is present (should be done on a bike stand).

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