Mavic Cosmic Creaking
Andy Leisner
excellent shape.
When I am climbing out of the saddle, they make a creaking noise. It sounds
like a tin-type sound and it seems to be coming from the hub/cassette area. I
use a Dura-Ace 9-speed cassette, and it makes this noise with either my 12-23
or my 12-21 cassette.
It is the wheel and not the bike, for my two other sets of wheels don't make
this nosie on my Look KG281. Also, when I have used the Cosmics on other
bikes, they still make the noise.
I have greased the cassette cogs and the cassette body, and I have lubed where
the spokes mount to the hub. No success though. It still makes this creaking
sound when climbing out of the saddle. In the saddle they are silent.
Any ideas??? Thanks.
Andy
Mark McMaster
I have heard several pairs of Mavics making this creaking
noise. It actually comes from the rim sockets moving in the
rim as the wheel is flexed from side to side when out of the
saddle. The sound can often be duplicated by grabbing a
spoke and yanking it sideways - especially the lower
tensioned left spokes. A drop of oil at each nipple around
the rim socket might help, although the real answer might be
in increasing the spoke tension to keep the sockets from
moving around.
Mark McMaster
MMc...@ix.netcom.com
Bob Mitke
>I have heard several pairs of Mavics making this creaking
>noise. It actually comes from the rim sockets moving in the
>rim as the wheel is flexed from side to side when out of the
>saddle.
Not to beat a dead horse, but from the response I got a
while back I thought I was the only one
that claimed wheels experience significant side loads...
Where were you five months ago when I could have
used a little help?
The side load necessary to cause spokes to completely
unload on a Cosmic (i.e, deep section rim which
reduces the effect of radial load on spoke tension) and
cause rim rattle is significant...
Your solution to eliminate the rattle (increased tension)
is a good one, but it doesn't eliminate the lateral wheel
loads...
-Bob Mitke
Rex Riley
.. and don't forget to check the long presta valve stem rattling
against the rim opening as a point source, too.
-r
Andy Leisner
the rim socket might help, although the real answer might be
in increasing the spoke tension to keep the sockets from
moving around.
>>
As a quick (read lazy) fix, I ran a drop of Tri-Flow down the nipple of the
spokes. I rode it this morning, and there was much less creaking. It is still
there, but GREATLY reduced, so it looks like it helped. I will take the tire
off and do it the right way now. Thanks to all that helped.
Andy
Mark McMaster
>
> Mark McMaster wrote:
>
> >I have heard several pairs of Mavics making this creaking
> >noise. It actually comes from the rim sockets moving in the
> >rim as the wheel is flexed from side to side when out of the
> >saddle.
>
> Not to beat a dead horse, but from the response I got a
> while back I thought I was the only one
> that claimed wheels experience significant side loads...
>
> Where were you five months ago when I could have
> used a little help?
If you'll recall, in the discussion a few months ago I was
on the side that positted that lateral forces during normal
riding were inconsequential.
> The side load necessary to cause spokes to completely
> unload on a Cosmic (i.e, deep section rim which
> reduces the effect of radial load on spoke tension) and
> cause rim rattle is significant...
The creaking in Cosmic wheels is not caused by the spokes
detensioning and allowing the rim sockets to rattle. The
creaking is caused by the rim sockets rotating and sliding
slightly as the wheel is flexed laterally. The sockets in
Cosmic Equipe/Elite wheels are not crimped in, but are loose
(if you shake an unbuilt rim you can hear them rattle).
Because the sockets don't conform exactly to the shape of
the rim, they can move slightly if the wheel is under a
small lateral load, resulting in the creaking sound that is
observed.
A further observation indicating that the noise is not
caused by spokes detensioning is that the noise can be
replicated by pulling spokes laterally. Such a lateral
force on the spokes increases, not decreases tension, yet
the sockets creaks just the same.
> Your solution to eliminate the rattle (increased tension)
> is a good one, but it doesn't eliminate the lateral wheel
> loads...
Increasing spoke tension decreases the creaking because the
extra force & friction on the sockets decreases their
motion. Although when standing and rocking the bike the
lateral loads on the wheel are not zero, they are still
small enough not be be consequential.
Mark McMaster
MMc...@ix.netcom.com
Bob Mitke
>If you'll recall, in the discussion a few months ago I was
>on the side that positted that lateral forces during normal
>riding were inconsequential.
I do recall that, which is why I asked the question. By
your own admission, now, the lateral loads when climbing
out of the saddle are large enough to cause significant
changes in the structural geometry of a wheel. These
significant changes are evidenced by a creaking sound.
The lateral forces required to cause such a geometry
change are larger than a few pounds...
>A further observation indicating that the noise is not
>caused by spokes detensioning is that the noise can be
>replicated by pulling spokes laterally. Such a lateral
>force on the spokes increases, not decreases tension, yet
>the sockets creaks just the same.
>
And when you pull laterally on these spokes, do you pull
with a force of a few pounds, or do you put some larger
load on it?
How do you think the lateral load applied at the tire,
in order to get the same change in spoke tension and
change in spoke/rim angle as when you yanked on just
one spoke, are related? I would suggest that you need
a larger lateral force applied at the tire to get the same
net spoke tension change as just yanking on a
single spoke...
>Increasing spoke tension decreases the creaking because the
>extra force & friction on the sockets decreases their
>motion.
Agreed. The spoke is allowed to pivot relative to the
sockets and the socket no longer rotates relative to
the rim. The structure deforms just as before, though...
This would be an opportunity for someone who has a
creaky wheel to contribute to this debate (similar to the
experiment I proposed five months ago that no one has
taken me up on). Take your creaky wheel, put it in
your bike. Turn your bike upside down and have a
buddy hold everything real tight.
Pull laterally on your wheel until it creaks. Estimate the
lateral load. I am guessing it is more than a few pounds
(i.e, > 5pounds) of side load to create the creak...
>Although when standing and rocking the bike the
>lateral loads on the wheel are not zero, they are still
>small enough not be be consequential.
I assume you meant to say they are small enough to
be considered inconsequential.
For an overdesigned 36 hole wheel. I agree.
For different flavors of wheels, I disagree...
-Bob Mitke
Mark Hickey
>Mark McMaster wrote;
>
>>If you'll recall, in the discussion a few months ago I was
>>on the side that positted that lateral forces during normal
>>riding were inconsequential.
>
>I do recall that, which is why I asked the question. By
>your own admission, now, the lateral loads when climbing
>out of the saddle are large enough to cause significant
>changes in the structural geometry of a wheel. These
>significant changes are evidenced by a creaking sound.
>
>The lateral forces required to cause such a geometry
>change are larger than a few pounds...
Where did you get "significant changes in the structural geometry of a
wheel" from what Mark wrote? There's nothing in his post that even
hints at such a thing.
Perhaps that's what you wanted it to say?
To restate his position, the creaking is caused by very, very slight
fretting movements of the eyelets against the rim material - in the
same way a bottom bracket can creak when there is microscopic movement
of the cup threads against the frame's BB shell. In neither case is a
"significant change in structural geometry" necessary, unless you
count it at the molecular scale.
The radial unloading and loading that goes on during every revolution
can also cause the same thing - there is no off-axis loading of the
eyelets if there IS lateral loading on the wheel anyway. It's just a
further reduction in spoke tension.
>>A further observation indicating that the noise is not
>>caused by spokes detensioning is that the noise can be
>>replicated by pulling spokes laterally. Such a lateral
>>force on the spokes increases, not decreases tension, yet
>>the sockets creaks just the same.
>And when you pull laterally on these spokes, do you pull
>with a force of a few pounds, or do you put some larger
>load on it?
You can't put a lateral load on a spoke while you're riding it, so
you're barking up the wrong tree trying to reopen the "lateral loading
of wheels" issue.
>How do you think the lateral load applied at the tire,
>in order to get the same change in spoke tension and
>change in spoke/rim angle as when you yanked on just
>one spoke, are related? I would suggest that you need
>a larger lateral force applied at the tire to get the same
>net spoke tension change as just yanking on a
>single spoke...
I'm curious as to why this would matter, one way or another though...
>>Increasing spoke tension decreases the creaking because the
>>extra force & friction on the sockets decreases their
>>motion.
>
>Agreed. The spoke is allowed to pivot relative to the
>sockets and the socket no longer rotates relative to
>the rim. The structure deforms just as before, though...
>
>This would be an opportunity for someone who has a
>creaky wheel to contribute to this debate (similar to the
>experiment I proposed five months ago that no one has
>taken me up on). Take your creaky wheel, put it in
>your bike. Turn your bike upside down and have a
>buddy hold everything real tight.
>
>Pull laterally on your wheel until it creaks. Estimate the
>lateral load. I am guessing it is more than a few pounds
>(i.e, > 5pounds) of side load to create the creak...
What would this prove? Only that unloading a spoke to a certain
amount might reproduce the creaking noise. It's independent of the
method of obtaining that unloading (or over-loading).
>>Although when standing and rocking the bike the
>>lateral loads on the wheel are not zero, they are still
>>small enough not be be consequential.
>
>I assume you meant to say they are small enough to
>be considered inconsequential.
"in" = "not" in this usage.
>For an overdesigned 36 hole wheel. I agree.
>
>For different flavors of wheels, I disagree...
Sigh....
Mark Hickey
Habanero Cycles
http://www.cynetfl.com/habanero/
Home of the $695 ti frame
Tim McNamara
<MMc...@ix.netcom.com> wrote:
> The creaking in Cosmic wheels is not caused by the spokes
> detensioning and allowing the rim sockets to rattle. The
> creaking is caused by the rim sockets rotating and sliding
> slightly as the wheel is flexed laterally. The sockets in
> Cosmic Equipe/Elite wheels are not crimped in, but are loose
> (if you shake an unbuilt rim you can hear them rattle).
When I recently rebuilt one of these with a new rim, the sockets were
wedge-shaped pieces that were a bear to deal with, because they come in
a bag completely separate from the rim. You have to slide them into
the cavernous shell of the rim and not drop them off, because they're a
real pain in the a** to get out.
The trick was to put the nipple on the spoke, the socket over the spoke
and on to the nipple, and slide the entire thing through the spoke hole
in the rim, then fixing the straight end of the spoke into the slot in
the hub flange. Except because of the design this could only be done
on the non-drive side. On the drive side you have to thread the spoke
through the hub flange first, greatly increasing your risk of dropping
a niplle socket into the rim. Sheesh.
> Because the sockets don't conform exactly to the shape of
> the rim, they can move slightly if the wheel is under a
> small lateral load, resulting in the creaking sound that is
> observed.
You are correct, the wedge profile of the sockets does not conform to
the inside shape of the rim cavity, which results in a concentrated
load on the rim walls and premature failure. The rim cracks at the
point where the "shoulder" of the niplle socket contacts the inside of
the rim wall.
In my case, the creaking noise in my Cosmic wheels was the sound of
cracks in the aluminum fretting against each other. If one of these
wheels creaks a lot, it whould be examined closely for cracks.
IMHO this is one crappy rim design.
> A further observation indicating that the noise is not
> caused by spokes detensioning is that the noise can be
> replicated by pulling spokes laterally. Such a lateral
> force on the spokes increases, not decreases tension, yet
> the sockets creaks just the same.
I was not able to replicate the creak in my wheels in this fashion.
> > Your solution to eliminate the rattle (increased tension)
> > is a good one, but it doesn't eliminate the lateral wheel
> > loads...
>
> Increasing spoke tension decreases the creaking because the
> extra force & friction on the sockets decreases their
> motion. Although when standing and rocking the bike the
> lateral loads on the wheel are not zero, they are still
> small enough not be be consequential.
Oh joy, we're back to this red herring.
Bob Mitke
>The radial unloading and loading that goes on during every revolution
>can also cause the same thing - there is no off-axis loading of the
>eyelets if there IS lateral loading on the wheel anyway. It's just a
>further reduction in spoke tension.
But, if you bothered to read the entire thread, the rider said in this
loading condition the wheel makes no noise. It only makes noise
when he stands out of the saddle...
I hope you didn't see an opportunity to try and get 'ol Bob, and
then immediately respond without actually reading the whole
thread...
>>>A further observation indicating that the noise is not
>>>caused by spokes detensioning is that the noise can be
>>>replicated by pulling spokes laterally. Such a lateral
>>>force on the spokes increases, not decreases tension, yet
>>>the sockets creaks just the same.
>
>>And when you pull laterally on these spokes, do you pull
>>with a force of a few pounds, or do you put some larger
>>load on it?
>
>You can't put a lateral load on a spoke while you're riding it, so
>you're barking up the wrong tree trying to reopen the "lateral loading
>of wheels" issue.
Again, if you bothered to read what Mark M said, you can see why I
asked the question. When you pull laterally on a spoke you
increase spoke tension. When you laterally load a bicycle
wheel, you increase spoke tension...
Try a simple experiment with this fundamental concept to
prove it to yourself...
>>How do you think the lateral load applied at the tire,
>>in order to get the same change in spoke tension and
>>change in spoke/rim angle as when you yanked on just
>>one spoke, are related? I would suggest that you need
>>a larger lateral force applied at the tire to get the same
>>net spoke tension change as just yanking on a
>>single spoke...
>
>I'm curious as to why this would matter, one way or another though...
Well, lets see, if Mark M says he has to pull on a spoke with
approximately 20 lbs of force to get the wheel to creak, and if
it takes more force applied at the tire to result in the same
_increase_ in spoke tension we can say that lateral loads
encountered while riding are larger than a few pounds...
>>Pull laterally on your wheel until it creaks. Estimate the
>>lateral load. I am guessing it is more than a few pounds
>>(i.e, > 5pounds) of side load to create the creak...
>
>What would this prove? Only that unloading a spoke to a certain
>amount might reproduce the creaking noise. It's independent of the
>method of obtaining that unloading (or over-loading).
Lateral loads are a component of how a wheel is loaded. To
a point, radial load has no effect on lateral stiffness. With a deep
section wheel like the cosmic, radial loads have an even smaller
effect on changes in spoke tension...
Applying a pure lateral load will lead to insight on the problem
with Cosmic creaks...
Again, you seem to be missing a fundamental concept related
to the bicycle wheel...
Spokes can increase in tension to a level higher than they were
initially tensioned during riding...
I hope you have been reading this entire thread and can contribute
in a meaningful way in the future...
I am still waiting for comments from you about my calculation of
'beaner factor of safety and how this might relate to wheel
factor of safety...
-Bob Mitke
Mark Hickey
>Mark Hickey wrote;
>
>>The radial unloading and loading that goes on during every revolution
>>can also cause the same thing - there is no off-axis loading of the
>>eyelets if there IS lateral loading on the wheel anyway. It's just a
>>further reduction in spoke tension.
>
>But, if you bothered to read the entire thread, the rider said in this
>loading condition the wheel makes no noise. It only makes noise
>when he stands out of the saddle...
>
>I hope you didn't see an opportunity to try and get 'ol Bob, and
>then immediately respond without actually reading the whole
>thread...
You overestimate your importance, methinks.
Bob, you seem to have "accidentally" left out the portion of your post
that inititated my reply. To be helpful, I'll add it below...
<snippage follows>
>I do recall that, which is why I asked the question. By
>your own admission, now, the lateral loads when climbing
>out of the saddle are large enough to cause significant
>changes in the structural geometry of a wheel. These
>significant changes are evidenced by a creaking sound.
>
>The lateral forces required to cause such a geometry
>change are larger than a few pounds...
<end of snippage>
To which I replied....
<snippage follows>
Where did you get "significant changes in the structural geometry of a
wheel" from what Mark wrote? There's nothing in his post that even
hints at such a thing.
Perhaps that's what you wanted it to say?
To restate his position, the creaking is caused by very, very slight
fretting movements of the eyelets against the rim material - in the
same way a bottom bracket can creak when there is microscopic movement
of the cup threads against the frame's BB shell. In neither case is a
"significant change in structural geometry" necessary, unless you
count it at the molecular scale.
The radial unloading and loading that goes on during every revolution
can also cause the same thing - there is no off-axis loading of the
eyelets if there IS lateral loading on the wheel anyway. It's just a
further reduction in spoke tension.
<end of snippage>
The rest of my reply just restates the same thing - that all loading
on a wheel is the same to a spoke. Whether it occurs from riding it,
leaning it, or placing it in a vice, the end result at the eyelet will
be identical. When you laterally displace a spoke by plucking it like
a banjo string, you're introducing an entirely foreign mode that has
nothing to do with riding a bike.
What didn't you understand about that?
And then you can explain to us about the "significant changes in
structural geometry" that occur in wheels.
Mark Hickey
Habanero Cycles
http://www.cynetfl.com/habanero/
Home of the $695 ti frame
>>>>A further observation indicating that the noise is not
Bob Mitke
>To restate his position, the creaking is caused by very, very slight
>fretting movements of the eyelets against the rim material - in the
>same way a bottom bracket can creak when there is microscopic movement
>of the cup threads against the frame's BB shell. In neither case is a
>"significant change in structural geometry" necessary, unless you
>count it at the molecular scale.
And how do you go about determining where that BB creak is coming
from? I usually wank on the cranks with my foot to determine
if the sound is coming from the BB. Mark M. suggested a similar
method of wanking on some spokes, to which I added the next
step of asking someone to wank on the tire/rim when fixtured in
a bicycle frame...
Seems like a reasonable, logical, method to diagnose the sound,
and gain some insight on the lateral forces needed to create
that sound...
>The radial unloading and loading that goes on during every revolution
>can also cause the same thing - there is no off-axis loading of the
>eyelets if there IS lateral loading on the wheel anyway. It's just a
>further reduction in spoke tension.
Please define your eyelet coordinate system (or perhaps you were
referring to a spoke coordinate system) so that I can try
to understand what it is you are talking about when you say off
axis...
Looking at the shape of a nipple, and the fact that it sits in a
round hole, I would think there is an expansion force at that
interface which is an off-axis force, but that is not what we
are discussing here...
Again as far as increases in spoke tension goes: Have you tried
the pluck test on a spoke while loading a wheel radially and
laterally? There is a significant increase
in pitch (i.e. it is plainly audible) if you pluck the appropriate spoke
while simultaneously applying the loads...
Try it out...
>The rest of my reply just restates the same thing - that all loading
>on a wheel is the same to a spoke. Whether it occurs from riding it,
>leaning it, or placing it in a vice, the end result at the eyelet will
>be identical. When you laterally displace a spoke by plucking it like
>a banjo string, you're introducing an entirely foreign mode that has
>nothing to do with riding a bike.
I think you are missing the point of my discussion with Mark M. He
suggested that he could make the noise by yanking on a spoke. I
asked him how hard he pulled and how that might relate to pulling
laterally on the tire (as in recreating an actual on the bike experience).
I suggested that someone with a creaky wheel try an experiment.
I agree with you that yanking on a single spoke isn't a re-creation
of anything you would see while riding the bike. Then again, I never
said that it was. I took the time to relate the experience
Mark M. had to an actual real-life situation of a lateral force acting
through the tire/rim...
>And then you can explain to us about the "significant changes in
>structural geometry" that occur in wheels.
In the case of the Cosmic, the change was significant enough to
be annoying. But this is semantics...
Like anything, it depends on the circumstances, but your standard
28/32 hole radially loaded wheel can deflect elastically
over 1/2 inch under a lateral point load (when measured at the rim
along the line of action of the lateral load).
What is the significance of that? That means you
could experience a lateral load large enough (on the order of 100 lbs)
to cause this displacement a bunch of times and you
would never even know it because your wheels would still be in true.
How does a lateral load this large effect the stress at the rim
eyelet and hub flange? Significantly enough that I wouldn't leave
those effects out of my analysis...
Does this magnitude of lateral displacement significantly change
the geometry of the wheel? If you ask me, the answer is yes...
What do you think, lets see, arctan(.5/13.5)... Is two degrees
significant? Considering that the spoke angle on the freehub
side of most dished wheels is in the ball park of 4 degrees,
I would hope you would agree that a 50% change in
geometry is significant...
Now, lets see, if your clearances aren't designed quite right, or
you use a spoke design that doesn't allow for this significant
change in geometry, you might have a wheel that falls apart in a
few thousand miles...
To me, that is significant...
Maybe your perception is different, or perhaps you ride wheels that
have the spokes attached to the rim and hub such that the
boundary condition at either end is fixed...
-Bob Mitke
Mark Hickey
>Mark Hickey wrote:
>
>>To restate his position, the creaking is caused by very, very slight
>>fretting movements of the eyelets against the rim material - in the
>>same way a bottom bracket can creak when there is microscopic movement
>>of the cup threads against the frame's BB shell. In neither case is a
>>"significant change in structural geometry" necessary, unless you
>>count it at the molecular scale.
>
>And how do you go about determining where that BB creak is coming
>from? I usually wank on the cranks
I'm sure that amused those with a more UK orientation....
> with my foot to determine
>if the sound is coming from the BB. Mark M. suggested a similar
>method of wanking on some spokes, to which I added the next
>step of asking someone to wank on the tire/rim when fixtured in
>a bicycle frame...
>
>Seems like a reasonable, logical, method to diagnose the sound,
>and gain some insight on the lateral forces needed to create
>that sound...
Ummmm, everyone had already determined it was the eyelet making the
noise. And that it was spoke tension variation that caused it.
>>The radial unloading and loading that goes on during every revolution
>>can also cause the same thing - there is no off-axis loading of the
>>eyelets if there IS lateral loading on the wheel anyway. It's just a
>>further reduction in spoke tension.
>
>Please define your eyelet coordinate system (or perhaps you were
>referring to a spoke coordinate system) so that I can try
>to understand what it is you are talking about when you say off
>axis...
Eyelet coordination system. Heh heh heh... you kill me Bob.
>Looking at the shape of a nipple, and the fact that it sits in a
>round hole, I would think there is an expansion force at that
>interface which is an off-axis force, but that is not what we
>are discussing here...
The issue is that you're plucking the spoke like a bass string. There
is no analagous situation while riding a bike.
>Again as far as increases in spoke tension goes: Have you tried
>the pluck test on a spoke while loading a wheel radially and
>laterally? There is a significant increase
>in pitch (i.e. it is plainly audible) if you pluck the appropriate spoke
>while simultaneously applying the loads...
>
>Try it out...
But what makes you think that it's not a DECREASE in tension that's
causing the problem? That will be much, much larger. Creaking is
usually the sound of micro-welds breaking. That happens when you
decrease the pressure between two surfaces.
>>The rest of my reply just restates the same thing - that all loading
>>on a wheel is the same to a spoke. Whether it occurs from riding it,
>>leaning it, or placing it in a vice, the end result at the eyelet will
>>be identical. When you laterally displace a spoke by plucking it like
>>a banjo string, you're introducing an entirely foreign mode that has
>>nothing to do with riding a bike.
>
>I think you are missing the point of my discussion with Mark M. He
>suggested that he could make the noise by yanking on a spoke. I
>asked him how hard he pulled and how that might relate to pulling
>laterally on the tire (as in recreating an actual on the bike experience).
>I suggested that someone with a creaky wheel try an experiment.
Funny, I have yet to "pull laterally on a tire" as an "on bike
experience".
>I agree with you that yanking on a single spoke isn't a re-creation
>of anything you would see while riding the bike. Then again, I never
>said that it was. I took the time to relate the experience
>Mark M. had to an actual real-life situation of a lateral force acting
>through the tire/rim...
Which is strictly a matter of spoke tension, plain and simple. Trying
to tie it in with your favorite crusade (lateral loading while just
riding along) is only muddying the water.
>>And then you can explain to us about the "significant changes in
>>structural geometry" that occur in wheels.
>
>In the case of the Cosmic, the change was significant enough to
>be annoying. But this is semantics...
>
>Like anything, it depends on the circumstances, but your standard
>28/32 hole radially loaded wheel can deflect elastically
>over 1/2 inch under a lateral point load (when measured at the rim
>along the line of action of the lateral load).
The rest is you beating the dead and buried horse again, so I'll go
watch the TdF instead (and wonder how those sprinters' wheels can
possibly stay together with all that lateral force on their wheels).
Mark Hickey
Habanero Cycles
http://www.cynetfl.com/habanero/
Home of the $695 ti frame
>What is the significance of that? That means you
Mark McMaster
> >>How do you think the lateral load applied at the tire,
> >>in order to get the same change in spoke tension and
> >>change in spoke/rim angle as when you yanked on just
> >>one spoke, are related? I would suggest that you need
> >>a larger lateral force applied at the tire to get the same
> >>net spoke tension change as just yanking on a
> >>single spoke...
> >
> >I'm curious as to why this would matter, one way or another though...
>
> Well, lets see, if Mark M says he has to pull on a spoke with
> approximately 20 lbs of force to get the wheel to creak, and if
> it takes more force applied at the tire to result in the same
> _increase_ in spoke tension we can say that lateral loads
> encountered while riding are larger than a few pounds...
You are putting words in my mouth. I didn't say what
lateral force on a spoke was required to make the rim creak,
and it was definitely far less than 20 pounds, probably only
a pound or two. The spokes most likely to creak were the
(lower tension) left spokes. Pulling the spoke to one side
of the wheel would create a short and quick creak sound.
Continuing to pull would have no effect, and the socket
wouldn't creak again until you pulled the spoke from the
other direction (also with only a pound or two of force).
This indicates that the creak is caused by a small fretting
type motion, as Mark Hickey said.
> >>Pull laterally on your wheel until it creaks. Estimate the
> >>lateral load. I am guessing it is more than a few pounds
> >>(i.e, > 5pounds) of side load to create the creak...
> >
> >What would this prove? Only that unloading a spoke to a certain
> >amount might reproduce the creaking noise. It's independent of the
> >method of obtaining that unloading (or over-loading).
>
> Lateral loads are a component of how a wheel is loaded. To
> a point, radial load has no effect on lateral stiffness. With a deep
> section wheel like the cosmic, radial loads have an even smaller
> effect on changes in spoke tension...
The creaking is caused by the socket rubbing against the rim
wall, which is a non-linear affect governed by such things
as static friction. Depending on the circumstances (such as
high vertical loads) the lateral force required to creak can
vary substantially (see below).
> Applying a pure lateral load will lead to insight on the problem
> with Cosmic creaks...
Not really. The amount of force required to make the nipple
socket move depends on the friction between the socket and
the rim, which is dependent on the normal force between the
socket and rim, which is supplied by the spoke tension.
Under the vertical load of the rider's weight the bottom
spokes are detensioned, reducing socket/rim friction, so it
would probably take even less lateral force on the spoke to
cause it to creak.
As further evidence, Mavic Cosmic Equipe/Elite/Expert wheels
use what is essentially the same rim (and sockets) as the
CXP-30, but CXP-30 rims don't creak. The major difference
seems to be that the Cosmic wheels use 18 or 20 spokes,
whereas the CXP-30 is usually used with 28 or 32 spokes.
With fewer spokes in the Cosmic, there are fewer spokes to
share the load in the Load Affected Zone, and therefore the
bottom spokes will detension more than with a CXP-30 for a
given load. This in turn means that it takes less lateral
force to make the sockets in Cosmic rims creak.
> Again, you seem to be missing a fundamental concept related
> to the bicycle wheel...
>
> Spokes can increase in tension to a level higher than they were
> initially tensioned during riding...
But not by much, and only in unusual circumstances - and
even then, tensions don't increase by as much as they
decrease during normal circumstances.
Mark McMaster
MMc...@ix.netcom.com
bobm...@my-deja.com
mhi...@cynetfl.com (Mark Hickey) wrote:
> bikes...@aol.comnojunk (Bob Mitke) wrote:
>
> >Mark Hickey wrote:
> >Again as far as increases in spoke tension goes: Have you tried
> >the pluck test on a spoke while loading a wheel radially and
> >laterally? There is a significant increase
> >in pitch (i.e. it is plainly audible) if you pluck the appropriate
spoke
> >while simultaneously applying the loads...
> >
> >Try it out...
>
> But what makes you think that it's not a DECREASE in tension that's
> causing the problem? That will be much, much larger. Creaking is
> usually the sound of micro-welds breaking. That happens when you
> decrease the pressure between two surfaces.
I too, initially thought it was a decrease in tension. Mark M.
clarified the point. The initial poster did say it only makes noise
when he was out of the saddle.
> Funny, I have yet to "pull laterally on a tire" as an "on bike
> experience".
Play the ball, not the man...
I believe it is safe to assume you correctly understood what I was
trying to communicate. Would you like me to fully expand on that topic
so you can fully comprehend what I was trying to say?
> >I agree with you that yanking on a single spoke isn't a re-creation
> >of anything you would see while riding the bike. Then again, I
never
> >said that it was. I took the time to relate the experience
> >Mark M. had to an actual real-life situation of a lateral force
acting
> >through the tire/rim...
>
> Which is strictly a matter of spoke tension, plain and simple. Trying
> to tie it in with your favorite crusade (lateral loading while just
> riding along) is only muddying the water.
Spokes can increase in tension also, which effects the design of the
parts it interfaces with. You should not overlook this additional
component when undertaking a thorough analysis...
Get enough supporting evidence and a case strengthens...
I wonder why Spinergy started selling those crazy plastic pieces that
go in between the spokes of their wheels...
> The rest is you beating the dead and buried horse again, so I'll go
> watch the TdF instead (and wonder how those sprinters' wheels can
> possibly stay together with all that lateral force on their wheels).
I wonder why particular sprinters, who don't have to worry about long
term durability of their wheels, prefer the extra beefy super stiff
style of wheels as opposed to the lightweight wheels...
-Bob Mitke
Sent via Deja.com http://www.deja.com/
Before you buy.
Mark Hickey
>In article <3964386e...@News.CIS.DFN.DE>,
> mhi...@cynetfl.com (Mark Hickey) wrote:
>> bikes...@aol.comnojunk (Bob Mitke) wrote:
>>
>> >Mark Hickey wrote:
>
>> But what makes you think that it's not a DECREASE in tension that's
>> causing the problem? That will be much, much larger. Creaking is
>> usually the sound of micro-welds breaking. That happens when you
>> decrease the pressure between two surfaces.
>
>I too, initially thought it was a decrease in tension. Mark M.
>clarified the point. The initial poster did say it only makes noise
>when he was out of the saddle.
Which would still indicate it's probably a decrease in tension that's
making the noise. When you're out of the saddle, the spokes are going
to see a higher range of tensions as the rider lurches around on the
bike (alternately weighting and unweighting both wheels).
>> Funny, I have yet to "pull laterally on a tire" as an "on bike
>> experience".
>
>Play the ball, not the man...
I might have put a smilely on that - but just couldn't help myself
when you put the two comments so close together.
>I believe it is safe to assume you correctly understood what I was
>trying to communicate. Would you like me to fully expand on that topic
>so you can fully comprehend what I was trying to say?
Of course not.
>> >I agree with you that yanking on a single spoke isn't a re-creation
>> >of anything you would see while riding the bike. Then again, I
>never
>> >said that it was. I took the time to relate the experience
>> >Mark M. had to an actual real-life situation of a lateral force
>acting
>> >through the tire/rim...
>>
>> Which is strictly a matter of spoke tension, plain and simple. Trying
>> to tie it in with your favorite crusade (lateral loading while just
>> riding along) is only muddying the water.
>
>Spokes can increase in tension also, which effects the design of the
>parts it interfaces with. You should not overlook this additional
>component when undertaking a thorough analysis...
>
>Get enough supporting evidence and a case strengthens...
But it has so little to do with this particular case that it's nothing
more than clutching at straws. A mechanical interface that's fretting
is in a very tentative state of equilibrium, and will respond to
slight changes of any type. I suspect if Mark McM had compressed the
rim to produce a similar DECREASE in spoke tension, he would have also
reproduced the creaking noise.
>I wonder why Spinergy started selling those crazy plastic pieces that
>go in between the spokes of their wheels...
Because the wheels were laterally flexible enough that even the
"normal" lateral loads encountered were enough to produce some lateral
displacement?
>> The rest is you beating the dead and buried horse again, so I'll go
>> watch the TdF instead (and wonder how those sprinters' wheels can
>> possibly stay together with all that lateral force on their wheels).
>
>I wonder why particular sprinters, who don't have to worry about long
>term durability of their wheels, prefer the extra beefy super stiff
>style of wheels as opposed to the lightweight wheels...
Explain this, please. I haven't seen any evidence that the riders
sprinting for the line in the current flat (boring) stages of the TdF
are riding anything other than "normal wheels". How would one go
about laterally stiffening wheels *significantly* unless you were at
liberty to change the width of the hub flanges?
Bob Mitke
>Bob Mitke wrote:
>> Well, lets see, if Mark M says he has to pull on a spoke with
>> approximately 20 lbs of force to get the wheel to creak, and if
>> it takes more force applied at the tire to result in the same
>> _increase_ in spoke tension we can say that lateral loads
>> encountered while riding are larger than a few pounds...
>
>You are putting words in my mouth. I didn't say what
>lateral force on a spoke was required to make the rim creak,
>and it was definitely far less than 20 pounds, probably only
>a pound or two.
Sorry for the confusion, I should have drawn more attention to
the word "if" in my first sentence...
>The spokes most likely to creak were the
>(lower tension) left spokes. Pulling the spoke to one side
>of the wheel would create a short and quick creak sound.
>Continuing to pull would have no effect, and the socket
>wouldn't creak again until you pulled the spoke from the
>other direction (also with only a pound or two of force).
I don't have a creaky wheel here, so I'll take your word for
it. I can't seem to get my BB to creak unless I really
WANK, er, push really hard on the crank with my foot...
Only one pound of force on the spoke doesn't change the
geometry of the wheel macroscopically. If the creak is this
sensitive to external loads, I would think the wheel would
creak non stop while riding on perfectly smooth pavement,
and not be limited to out of the saddle efforts as the original
poster described...
Something just doesn't sound right, but since I don't have the
wheel here I can't really contribute any more deeply...
>As further evidence, Mavic Cosmic Equipe/Elite/Expert wheels
>use what is essentially the same rim (and sockets) as the
>CXP-30, but CXP-30 rims don't creak. The major difference
>seems to be that the Cosmic wheels use 18 or 20 spokes,
>whereas the CXP-30 is usually used with 28 or 32 spokes.
>With fewer spokes in the Cosmic, there are fewer spokes to
>share the load in the Load Affected Zone, and therefore the
>bottom spokes will detension more than with a CXP-30 for a
>given load. This in turn means that it takes less lateral
>force to make the sockets in Cosmic rims creak.
But if it only takes one pound of force pulling laterally on the
spoke to make the thing creak, I don't see how a few more
spokes would suddenly make the wheel stop creaking.
If standing out of the saddle only puts 3 pounds of lateral
force on a wheel, the wheel should not be silent when
sitting on the saddle. As you said, the spoke tension
variance due to normal radial loads dwarfs the spoke tension
variance due to a three pound side load...
Is there a magical threshold for wheel creaks at 2.0125
pounds of lateral force that I am unaware of?
Something is not consistent...
Perhaps the additional spokes provide enough additional
stiffness that the structure deforms less under a given load.
Probably a little of both of our analysis' come into play at
one time or another I would reckon...
>> Spokes can increase in tension to a level higher than they were
>> initially tensioned during riding...
>
>But not by much, and only in unusual circumstances - and
>even then, tensions don't increase by as much as they
>decrease during normal circumstances.
Well, lets look at some numbers...
Step 0: Observe.
My wheels deflect under side loads. I wonder how that effects
spoke tension?
Step 1: Analysis (FEA)
Rear Wheel: 32 Revolution spokes. 19 mm box section rim.
Load case 1: 150 pound radial load.
peak decrease in spoke tension: ~70 pounds
peak increase in spoke tension: ~10 pounds
Load case 2: 50 pound side load applied from the cassette side.
peak decrease in spoke tension: ~75 pounds
peak increase in spoke tension: ~75 pounds
The spoke tension changes are on the same order of magnitude
when you are comparing normal radial loads and what I deem to
be a normal side load... Granted, the frequency of the side load
is not anywhere near the frequency of the radial load, but it still
needs to be considered (just as torsional loads and their effect
on spoke tension need to be considered)...
Phil Holman commented on what Boeing uses as a cutoff for
frequency of loading and whether it is ignored. As I recall, he
said anything that has greater than 0.1% (or was it .01%?) of
the total cycles gets looked at. When I go riding I stand up
for more than .1% of the time (.1% of one hour is what,
4 seconds?)...
Step 2: Does the analysis correlate with my own experience?
Can I make the non cassette side spokes go loose by pressing
laterally with about 50 lbs? Yes. Do the spokes on the cassette
side audibly increase in pitch? Yes.
The magnitudes of my analysis may not be 100% perfect, but
they are certainly not off by an order of magnitude...
When I did my analysis, I came to the conclusion that the change
in spoke tension (and the associated effects
due to the change in geometry) due to lateral loading should not
be ignored when designing bicycle wheels...
Step 3: communicate the results:
I have been trying for a while now...
-Bob Mitke