Should I be concerned about a clunk noise?

[Coaster]

I recently overhauled the bottom bracket on my aluminum Specialized Allez
Elite, primarily to get rid of the creaking noise it was making. The
creaking noise is gone, but it's been gradually replaced by a low clunk
during pedaling, but the noise is not in sync with any pedal strokes and has
no set rhythm. It will even occur a second or two after I stop pedaling,
but not when I've been coasting for a while.

I inspected the bottom exterior of the BB shell and noticed a line that
could either be a stress crack or maybe just an impression from
manufacturing.
The line is hairline thin, perfectly straight and perpendicular to the bike
frame, so it makes me think that it could be manufacturing related. I can
almost make out a separation of metal but it's really hard to be sure and I
can't feel it.

My question is could a low clunk noise during pedaling as I've described
above be indicative of a cracked frame, perhaps from shear stresses building
up and then being relieved? The bottom bracket shell seems a likely place
for a stress crack given there's a lot of load going through that area.
The bike is an '05 that is ridden almost daily and has one low speed crash.




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[Biker Winterizer]

lube dirt in it or cold frozen, rest a day walk hull hills shorter ri.

biking the year thru and not like years before.

 

[di]

"Biker Winterizer" <[email protected]> wrote in message
news:[email protected]...
> lube dirt in it or cold frozen, rest a day walk hull hills shorter ri.
>
> biking the year thru and not like years before.


Huh?

 

[Bill Sornson]

Biker Winterizer wrote:
> lube dirt in it or cold frozen, rest a day walk hull hills shorter ri.
>
> biking the year thru and not like years before.

gene???

 

[Biker Winterizer]

chain wheel in de rail dirt in turn peddle in frame cold weather snow
dirt get in oil lube make clunk noise in wilderness snow pack roads zero
temps echo sounds from pack ground.
if keep bike out side wait a day clunk sound gone take hills slow and
walk up so not break wheele d reil and chain break and reil crank stuck
put in wheel spoke and chain and other cale ice freeze stop to clunk k e
here better in winter ime.

biking the year thru and not like years before.

 

[Dave Larrington]

I'll have what he's having...

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Hoc ardur vincere docet.

 

[Bill Sornson]

Biker Winterizer wrote:
> chain wheel in de rail dirt in turn peddle in frame cold weather snow
> dirt get in oil lube make clunk noise in wilderness snow pack roads
> zero temps echo sounds from pack ground.
> if keep bike out side wait a day clunk sound gone take hills slow and
> walk up so not break wheele d reil and chain break and reil crank
> stuck put in wheel spoke and chain and other cale ice freeze stop to
> clunk k e here better in winter ime.
>
> biking the year thru and not like years before.

OK, you /gotta/ be related to gene.daniels!

 

[Coaster]

> Unexplained clunk
>
> Always be concerned about any unexplained noise until you have tracked
> down the cause. Ditto any unexpected crack in a frame, particularly
> alloy - it's more brittle than steel, and it could fail suddenly
> without much prior warning. Get it to a good bike shop and have them
> check it over. Don't trust it until it is checked out.
>
> Not having seen your frame, I couldn't be certain what caused the
> creaking. If it's any help (and it may not apply to your frame
> depending on its construction), my pal had an annoying creak on his aly
> framed bike last year. We tried everything with the bottom bracket, even
> totally dismantling and rebuilding it, all to no avail. The chainstays
> and seatstays, however, weren't welded together, but had a joint at the
> rear drop outs, held together by an allen bolt, and the creak turned
> out to be this joint working to a minute degree. Tightening the allen
> bolt stopped it. If yours has the same detail and the creak has
> returned, I would suggest checking that joint.
>
> Also check how tight the cranks are on the b/b axle. These could clunk
> if slightly loose, but this would be in time with your pedalling, and
> happen as you passed top or bottom dead centre, so seems unlikely
> since you say it isn't in time with pedalling.
>
> Is it in time with the chain travel time (the time it takes for the
> chain to travel round the transmission). If so check for tight links or
> the chain having a problem passing through the derailleur cage.
>
> It might turn out to be be a minor problem, but for your own safety
> don't ignore it until you have been able to discount any serious
> problems.
>
>
> --
> willarch


Thanks for a response I can understand.

From what I can tell the low clunking noise is not linked to pedal strokes
or chain travel. It does seem related to acceleration forces. When I start
out or accelerate to speed, I will hear it intermittently. After moderate
to hard acceleration I will hear the noise even when I stop pedaling for a
few seconds. That's why I think it's a result of build up of stresses in
the frame or other component and then the actual noise occurs when those
stresses are relieved somehow. In my mind's eye I can see a crack that will
cause the metal on each side to slide or shear thereby creating the noise.
Your suggestion of taking it to my bike shop is well taken and I will have
them examine it carefully. One nice thing about the bike is the frame is
warranted for life by Specialized.

One other thing I noticed that I haven't mentioned in my original post is
that when I stand on the pedals during acceleration I can hear a vibration
or buzzing coming from the BB region. I can even create the buzzing by
leveling the pedals and standing on them while coasting. I'm not sure if
this is related to the clunking noise, but it's coming from the same area.



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