New noise puzzling me!

[Tollers]

First post in a loooong time

I've developed a new noise on my bike when in the small chainring. Not a click, but a whirring timed with my pedal strokes. It doesn't really happen at all in the big ring though.

I've torqued chainrings bolts, rebuilt BB, cleaned casette, relubed wheel bearings, torqued pedals

The only idea i have is that i moved from oiled chain to waxing it, but I can't explain why that would only affect the small chainring. I'm not gratuitously crosschaining either and can't find any rubbing.

This video highlights the noise. At 37secs or so i shift into lower chainring and the the sound starts. Any ideas?


View: https://www.youtube.com/watch?v=2TA18D10Q_c

 

[simon.r]

Front mech cable end catching on something as you pedal? I know that's something I've had that frustrated the hell out of me for a while!

 

[Racing roadkill]

Try adjusting the B screw on the rear mech to increase the angle of dangle.

 

[Tollers]

Try adjusting the B screw on the rear mech to increase the angle of dangle.

Good idea. I haven't changed it's adjustment for several years, so not sure why it would have started now, but worth a try.

 

[lpretro1]

Sounds like the chain just touching the front derailleur ever so slightly - check & adjust low screw

 

[Tollers]

Sounds like the chain just touching the front derailleur ever so slightly - check & adjust low screw

That's what i thought too initially, but checked and checked and then adjusted to give it loads and loads of clearance. It's definitely not chainrub on front mech.....but it really does sound like it.

 

[Yellow Saddle]

Show us a picture of that chainring side-on, chain off please.

 

[Tollers]

Show us a picture of that chainring side-on, chain off please.

OK. I moved the chain onto the big ring to get it out of way. Is this the view you were looking for, or profile view to check that chainring isn't warped? The chainset has done about 5000 miles max.

Profile view:
View: https://www.youtube.com/watch?v=OcfaUmFcKL8

 

[Yellow Saddle]

OK. I moved the chain onto the big ring to get it out of way. Is this the view you were looking for, or profile view to check that chainring isn't warped? The chainset has done about 5000 miles max.

Profile view:
View: https://www.youtube.com/watch?v=OcfaUmFcKL8


View attachment 343482

Thanks, but I didn't see what I thought I might see. Thinking cap back on.

 

[Yellow Saddle]

Have you measured the chain for wear?

 

[Tollers]

Thanks, but I didn't see what I thought I might see. Thinking cap back on.

I'm curious what you were expecting......just for future reference (and my OCD)

 

[Tollers]

Have you measured the chain for wear?

Chain is only a few months old. Just checked and it's way less than 0.75% stretch, probably half that.

 

[Yellow Saddle]

I'm curious what you were expecting......just for future reference (and my OCD)

When a chain and chainring (not cassette) are out of pitch because the chain is elongated through wear, the incoming tooth hits against the next chain roller and then forcibly slides past it, creating a noise and vibration through the frame. That vibration sounds a bit like that in your video. However, it generally requires a very worn chainring where the individual cogs (teeth) are worn away on their pressure faces, the so-called shark-fin stage. The cog now no longer enters the chain and finds a perfect space, but finds a roller.

Your chainring is still good, but if the chain is really elongated, this would also happen with a brand new chainring. You can probably visualise what I say. I hope.

Measure the chain for us, let's see.

 

[Yellow Saddle]

Chain is only a few months old. Just checked and it's way less than 0.75% stretch, probably half that.

Chains don't care about time. How long is 12 links of the chain in inches?

 

[Yellow Saddle]

That chain looks awfully dry judging from the dry deposits on the chainring. Give it oil and give it another go. Small chainrings are noisier because the links articulate more.