Noise on the little ring.

[2Loose]

I've been trying to identify a noise that only occurs while on the little ring, particularly when grinding. (Tiagra Hollowtech 2)

To start with, I have completely ruled out the front mech rubbing on the chain. Or the BB.

It sounds like the chain is being strained somehow, particularly on the lower gears on the cassette. The sound completely vanishes on the big ring.

The bike is about 4.5k miles old and on the third chain and second cassette (both were changed together last time) so I am starting to think that the little ring has too much wear and perhaps it is time for a new chainset\chain & cassette.

Is there any rule of thumb for chainring wear, or easy way to check this?

 

[Muddy Ground]

Have you checked the tightness of the rear wheel quick release skewer? Sometimes the torque in the small front ring / rear large cog can be enough to strain this if not done up tightly, and it sounds horrible. Mine does it unless done up really tight.

PIJ

 

[Globalti]

The upper jockey wheel is probably running on the chain on the biggest cog. You can pull it away from the cog by tightening the B tension screw; this is a little screw on the main derailleur pivot facing backwards, when you tighten it it increases the tension on that vital pivot, which will pull the derailleur away from the cassette.

 

[2Loose]

You sir, may well be a genius! I read your post while waiting at the dentist so when I left I gave the rear skew a quarter of a turn.
Much reduced groaning on the little ring now.

I'll go for another bit of a turn when I leave work, but the results so far are positive.