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Discussion Starter · #1 ·
Hello I have a trek emonda with a Ultegra groupset..Ive noticed some noise in my chainring crank area when I'm doing long climbs in the lowest gear(small ring largest cog)...It is loudest in this year and when it's under load like climbing


.Sometimes when I notice it I'll trim up causing the inner cage to rub against the chain and the noise changes a bit...

I've checked my clearance with the chain and inner cage and I have about 1mm of clearance so I'm not sure where the noise can be coming from..Any ideas on what I can check?

Thanks
 

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If you're not getting rub on the inner cage of the derailleur it might just be chain noise at the chain hits the small ring. It's leaving the large cog and hitting the small ring at quite an angle and it's not nearly as quiet as it would be 4-5 cogs down.

It is really hard to say without having the bike in my stand or being able to ride it. This is my best guess.
 

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Sounds like a chainline issue, if you've discounted front derailleur rub. Check to see if the rear derailleur pulleys are in vertical alignment with the frame, and in the same plane as the frame i.e., not angling left or right. Those would be signs of a bent or loose derailleur hanger (tighten the bolt) or a bent derailleur cage.
 

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Chainline would be a frame issue, or possibly but highly unlikely where the cassette sits on the hub. If the frame was out of alignment a bunch and causing chain noise in certain gears, that's technically 'chainline'. If the hanger is bent and the chain isn't coming through the pulleys correctly and making noise as they come up onto the cogs, that isn't 'chainline', it's a bent hanger. It's really really rare to have any actual chainline issues these days.
For those that don't know, chainline is a measurement from the exact centerline of the frame. It's a measurement of how far out from the centerline of the frame the chainrings and cogs are. It used to be commonly referenced when figuring out which length crank axle/bottom bracket to use.
 

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The question here is "noisy" relative to what?

If I have everything on my road bike set up *perfectly*, there's still going to be more noise in the lowest gear, under load, than in any other gear (assuming no cross-chaining). My bike can be absolutely silent in the middle of the cassette, even in 2nd gear, but in 1st you will simply hear the chain on the cogs more. It's less noticeable if I've recently oiled my chain (and I run a thick chain oil).

This doesn't mean you don't have a problem. Bent hanger, low limit slightly off, RD adjustment off by just a hair – all of those are possibilities.

But the big question for me would be: do you have an underlying issue that is exacerbated or highlighted in the lowest gear, or is it just that your drivetrain is audible in the lowest gear?
 

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Hello I have a trek emonda with a Ultegra groupset..Ive noticed some noise in my chainring crank area when I'm doing long climbs in the lowest gear(small ring largest cog)...It is loudest in this year and when it's under load like climbing


.Sometimes when I notice it I'll trim up causing the inner cage to rub against the chain and the noise changes a bit...

I've checked my clearance with the chain and inner cage and I have about 1mm of clearance so I'm not sure where the noise can be coming from..Any ideas on what I can check?

Thanks
I say its your fd slightly out of adjustment by your statement above. If you have 1mm of clearance not under load, its probably rubbing under load. The chain will move inboard slightly under heavy load in the large cog. If trim makes the same noise change, its rubbing on the fd.
 

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Another possibility is the adjustment of the "B" screw. If the RD is too far forward, the top pulley can touch the cassette cog making noise. Tightening the "B" screw will move the RD away from the cassette.
 

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If the hanger is bent and the chain isn't coming through the pulleys correctly and making noise as they come up onto the cogs, that isn't 'chainline', it's a bent hanger.
Wouldn't you also have shifting problems if this is the case?
 

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Another possibility is the adjustment of the "B" screw. If the RD is too far forward, the top pulley can touch the cassette cog making noise. Tightening the "B" screw will move the RD away from the cassette.
Definitely something to check!
 

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Another possibility is the adjustment of the "B" screw. If the RD is too far forward, the top pulley can touch the cassette cog making noise. Tightening the "B" screw will move the RD pulley away from the cassette.
Fixed.
 

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I say its your fd slightly out of adjustment by your statement above. If you have 1mm of clearance not under load, its probably rubbing under load. The chain will move inboard slightly under heavy load in the large cog. If trim makes the same noise change, its rubbing on the fd.
Agreed. Especially consider it's only happening in that gear combination.

Google about limit screws (if you don't already know) then go for a ride with a small screwdriver and when you get to a hill that'll recreate the situation, back the limit off so it's not even close, then try. Then when you readjust back don't get as close to where you started (assuming backing it way off eliminates the noise, if not at least you're eliminated on possibility.)

I'd had this happen when climbing or sprinting when everything looks fine. That's why I'm suggesting you do this on the road because the rub may only be happening when you pedal hard.
 

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Discussion Starter · #15 ·
Agreed. Especially consider it's only happening in that gear combination.

Google about limit screws (if you don't already know) then go for a ride with a small screwdriver and when you get to a hill that'll recreate the situation, back the limit off so it's not even close, then try. Then when you readjust back don't get as close to where you started (assuming backing it way off eliminates the noise, if not at least you're eliminated on possibility.)

I'd had this happen when climbing or sprinting when everything looks fine. That's why I'm suggesting you do this on the road because the rub may only be happening when you pedal hard.
If adjusting the lower limit, what else needs to be adjusted with it? Cable tension?
 

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Wouldn't you also have shifting problems if this is the case?
Generally yes. The noise would also get worse as you downshift to larger cogs.

If adjusting the lower limit, what else needs to be adjusted with it? Cable tension?
Depends on whether your derailleurs and cable tension were correct in the first place. Since it looks like the bike wasn't set up correctly from the start it's not possible to say, but if it was...then yes, you'd have to reduce cable tension a bit to let the derailleur move inward to the new low limit screw setting.
 
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