Tech Strange noise

Bartek

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Jun 28, 2010
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#1
Hello. Just wondering if anyone could help.

Recently, I started hearing a strange noise coming from somewhere under or behind me when I'm riding.

It's very irregular and one day it happens more than another day. Also, it happens at certain speeds, usually over 25km/h.

It's sort of a hollow sound as if a cable housing was hitting the frame (impossible) or kind of like when you lightly flick the frame with your finger nail.

The frame is aluminum.

Any ideas?
 

kiwisimon

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Dec 14, 2006
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#2
Some shifter wire from the front derailler hiting the crank.
Check your pump is on tight, a loose screw in a bottle cage.

Might be the bike protesting it's impending sale.
 

Bartek

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#4
Thanks for the quick reply.

I forgot to mention the fact that it happens during pedalling as well is coasting. I suppose that excludes the BB or the pedal bearing.
It also happens on a flat, smooth surface and not on rough surface or bumps.
 

DeltaForce

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Sep 17, 2011
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#7
First thing that came to mind was that you'd not gotten all your spokey dokeys off after some kind of nostalgia trip. But they'd go silent as you got faster, as you can see in this helpful vid. All kinds of bicycle noises there to give you some ideas.

Bicycle Sounds
 
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Gunjira

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Oct 2, 2009
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#8
Don't want to be discouraging, but noise from my last alu frame from that area was the end of it. If the noise changes regarding to bike tilt, it's might be chainstays. Check for cracks, do some cleaning with flowing water.


Sent from my iPhone using Tapatalk
 

DeltaForce

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#9
Could be a cable end sitting very close to the frame. Rear brake, or mechs?

Does it happen in the big or small ring only? Cable end would be pulled closer to the frame depending on your mech. That would explain the intermittent nature of the problem. Could also explain the speed related symptom, as wind speed increases. Wind would be different on different days, too.
 

Bartek

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#12
Under and behind you, you say? Well that narrows it down for sure. We know for definite it is your bike and not the rest all the matter in the entire universe.

1. Does it happen when spinning, or when under power?

2. Does it happen when you stand up, and / or when you sit down?

3. Is it a regular sound, like ping ping ping ping ping ping, or is it an irregular PING, which then doesn't happen for a while, until you get a PING again?

First thing to do;

Take everything off the bike that isn't the bike itself; all bags, pumps, cuddly toys, etc., then go out and test it. Post back your results.

The only way to deal with unusual sounds on a bike is to A; be a hero who can identify any bike problem in a matter of seconds. B; work it out through a process of elimination.

LOL at 'maybe it is rim related' from the bike shop. I translate that as 'we don't know what we are talking about and don't know how / can't be arsed to find the source of the problem.'
I tried to pin point it, but since it happens only while riding at speeds over 25km/k, it's not easy.

It happens both when pedalling and coasting at higher speeds.
It is a very irregular PING.
I have taken everything off the bike already - no change.

As for the bike shop, it was my exact impression.
 

Bartek

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#13
That makes no sense. I assume by this you mean that you can only hear it when you are on flat / smooth surfaces, due to the relatively noisy nature of riding on a rough surface which will mask the sound you are experiencing?
What I mean is I tried to ride over rough surfaces or bumps, but it did not increase. It is still a "once in a while" thing. There is no difference between smooth and rough surfaces. And the noise is too loud and a very specific PING to be masked by rough surfaces.
 

Bartek

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#14
Could be a cable end sitting very close to the frame. Rear brake, or mechs?

Does it happen in the big or small ring only? Cable end would be pulled closer to the frame depending on your mech. That would explain the intermittent nature of the problem. Could also explain the speed related symptom, as wind speed increases. Wind would be different on different days, too.
I checked the cable end. I'm afraid it's not the source.
It tends to happen more in the small ring, but then again I ride more in the small ring.
 

kiwisimon

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#15
Aluminium bikes are great at amplifying sounds. If you are in the small gear it could just be due to a slack chain. If you have stripped the bike it must be either wheels, drivechain or brakes, it happens at idle so it's not front end of the drive chain. Does it do it when you have it in a bike repair stand? Check your spoke tension.
 
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zenbiker

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#17
The last time I heard a strange noise coming from the rear of the bike, it turned out to be a very angry aggressive dog!
My advice would be to keep going as fast as possible.

Also try taking the seat post out, grease it up and put it back in.
 

Bartek

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#18
Thanks all for suggestions.

It is hard to describe a thing like this in words.
Anyway, I will take it apart again, clean it well, tighten all the bolts and see what happens then.

Interestingly enough, it wasn't there today as I rode to and from work. I checked while sitting, standing, tilting it, riding over bumps, sprinting and braking suddenly, all at low and high speeds. Nothing. Warmer weather or a miracle? No idea.

Thanks again.
 

Bartek

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#19
The last time I heard a strange noise coming from the rear of the bike, it turned out to be a very angry aggressive dog!
My advice would be to keep going as fast as possible.

Also try taking the seat post out, grease it up and put it back in.
Ha ha. I know what you mean. I do get chased sometimes by angry monkeys making all kinds of weird noises.