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[Closed] "Tractor" sound on middle ring - WTF?

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[#9583887]

New SLX M7000 rear mech, new SLX cassette, new chain, new cable...

The gears shift perfectly, as expected from new bits. When back-pedaling the chain stays on the exact gear. The chain's fed through the derailleur properly, the B-screw's set to leave optimum clearance between the cassette and top pulley.

The bike is 3x10 setup, with SLX M672 crankset. When on the lowest or biggest chainring everything is smooth, quiet and lovely. But when on the middle ring I can hear and feel through my feet this uncomfortable "tractor" sound, on any rear sprocket combination. It is much stronger when pushing hard on pedals.

I've ran out of the ideas what's wrong. When I'm turning the pedals with the bike on a stand this annoying thing does not occur, only during a ride. The middle chainring visually looks decent (the crankset is 20 months old).

Am I missing something? Can this be the chainring?


 
Posted : 02/10/2017 10:19 am
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chaing striking the front derailleur? is it more noticeable when the chain is higher or lower gear on the cassette?


 
Posted : 02/10/2017 10:23 am
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middle ring is worn maybe?
only under the load of pedalling does this sound occur.
IME after a few rides, the ring will wear into the new chain. Although not optimal, this might cure the noise. Otherwise, get a new middle ring.


 
Posted : 02/10/2017 10:25 am
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chaing striking the front derailleur? is it more noticeable when the chain is higher or lower gear on the cassette?

I looked at this possibility and during a ride last night I adjusted the front mech using the shifter's barrel, so there was plenty of clearance between the chain and each side of the derailleur. It doesn't sound like the typical chain
rub to be honest.

My first reaction was few English and Polish swear words as I thought that I had fed the chain wrongly through the rear mech - it did feel like the chain was on the wrong side of the little lip on the cage in-between the pulleys. However it is not the issue.


 
Posted : 02/10/2017 10:40 am
 Yak
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Worn chainrings sound like tractors.


 
Posted : 02/10/2017 10:41 am
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Middle ring is worn


 
Posted : 02/10/2017 10:42 am
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Thanks guys! Shopping time ๐Ÿ˜‰


 
Posted : 02/10/2017 10:49 am
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My French mate's lad had this recently.

Turned out it was the hair on his legs rubbing on the saddle.

Never heard of this before, but they are an exceptionally hirsute family, especially the lad.
In fact, he's a mass of fur, Gaston.


 
Posted : 02/10/2017 10:49 am