Such a thing as crankflex?
John Haas
I built a bike to use for duathlons which I dearly love but it has a
problem that is driving me crazy. It is a double chain ring, 10 speed
Ultegra equipped XRP Cion frame road bike. When the chain is on either
the smallest cog or the 2nd smallest cog, there is a noticeable
clicking noise coming from the area of the front derailleur. It can be
heard only when I am pedaling hard. I have had the bike into two
different bike shops but no one can correct the problem. The last
mechanic told me it was either the frame flexing or the crank flexing
or both. If the frame is flexing then I guess I'm SOL (unless I want
to replace the frame). If it's the crank then I can do something about
that. Is crankflex common or is the likely culprit the frame? The
crank is a Ritchey which I chose because it was cheaper and lighter
than the Ultegra. I would hate to switch to an Ultegra crank and still
have this infernal noise.
Thanks.
Chris
There should be an inbetween position which allows for this. It's
usually used if you are in small chainring and 1st-3rd cog in back, or
big chanring and 9th-7th cog in the back. It is usually more of a
cross gearing issue which leads to the sound you hear. The crank does
deflect (flex) some, but so does the frame.
Chris
Chris
> big chanring and 9th-7th cog in the back.
Sorry, I meant 8th-10th.
Chris
John Haas
This happens when I'm on the big chainring so it can't be a cross
gearing issue.
pm
> On Wed, 4 Feb 2009 21:14:38 -0800 (PST), Chris
>
It can still be a trimming issue. For instance a click every pedal
revolution could be caused by the crank contacting the derailleur
outer cage plate.
-pm
Ron Ruff
> Is crankflex common or is the likely culprit the frame?
Probably neither. I had this on one of my bikes and noticed that the
chainring was not completely "true". Actually it was the mounting
points on the crank that were out of plane, or maybe the BB mounting
area, but it was easier to get a big crescent wrench and gently bend
the chainring so it would run straight. Problem solved.
There is a little flex of course. On this crank the ring happened to
veer outward where the crank was at 90 degrees, so the flex added to
the issue and made the ring rub on the cage. I have another crank
where the ring veers slightly inward at the same point, and there is
no need to fix that.
raa...@gmail.com
sometimes the bolts holding the chainring have loosened and perhaps
some dirt has gotten in between as well; you can take out the bolts
remove the chanirings and make sure mating surfaces and threads are
absolutely clean ( dunk in a bucket of varsol will do) then lube and
reinstall to recommended torque (tight)
Chris
> gearing issue.
It can happen in either chainring, but if it happens in the big ring,
and the 1st-2nd cogs, then it's more likely the front derailer is not
adjusted correctly. The following are the most likley options:
Cable adjustment is too loose, but not by much. 1/2 a turn to 1 turn
out on the barrel adjuster should sort it.
Limit screw is adjusted too in. 1/2 a turn to 1 turn out on the high
limit should sort it.
Derailer position/chain ring not true/crank not true
The trim could still be an issue. If the limit screw is too far in and
the cable adjustment is too tight, the shifter may "click" in to the
trim position and not the actual high setting. The chain may climb
into the big gear, but not have the designed clearance for the chain.
Chris
John Forrest Tomlinson
lh...@planet.nl
wrote:
> The word is "cranksetflex"
One crank can't flex?
Lou
Tom Sherman
> The word is "cranksetflex"
>
--
Tom Sherman - 42.435731,-83.985007
"Those who can't do, teach,
those who can’t teach, teach gym" - Anon.
John Forrest Tomlinson
Opps, youre right, but the word you mean is "crankarm."
So the phenomemon is "crankarmflex."
John Forrest Tomlinson
<sunset...@REMOVETHISyahoo.com> wrote:
>John Forrest Tomlinson wrote:
>> The word is "cranksetflex"
>>
>No, it is "crankarmsetflex". ;)
Right.
Jay Beattie
Flex related rubbing usually occurs on the big ring and is usually
caused by BB/frame flex, but you can get flex in a crank, which you
can feel at the bottom of the stroke. Your problem sounds like you
could have a chain that is too long, that you have cross-chaining or
your front derailleur is mispositioned. Like others mentioned, it
could also be loose mounting bolts or a warped ring. -- Jay Beattie.
A Muzi
>> The word is "cranksetflex"
Tom Sherman wrote:
> No, it is "crankarmsetflex". ;)
Did you mean "Crankarmsetflex Syndrome"? The horror!
Let's get a program funded[1] before more suffer! Think of The Children!
[1] Recovery! A billion or so oughta sneak in below notice. Call it
CARP, Crankarmsetflexsyndrome Asset Recovery Program.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
Frank Krygowski
The bike shop responses don't make sense to me. Flex doesn't cause
noise unless something is loose & shifting, or unless something is
hitting something else. It sounds to me like they haven't located the
problem and are just guessing.
I've had friends bikes that had (said the shop) supposedly incurable
noises. The latest one (on an old bike) turned out to be generated
within the freewheel - but it wasn't a once-per-revolution noise. It
came and went with maddening randomness. I found it by loading the
cranks, as described below, and rocking the bike back and forth as I
sat on it.
If your noise is once per revolution, it's probably in the front half
of the drive train one way or another. I'd get the bike in the
offending gear, ride to generate the noise, and note the exact crank
position. Then get into your garage, workshop, or wherever it's
quiet, and work the bike back and forth through that crank position
while maintaining strong pressure on the cranks. See if you can
replicate the noise while not riding, and locate it with a helper.
I've found clicks from the following: Loose crank bolts; loose crank
arms at the crank axle attachment; loose bearing cups or bearing lock
rings; various loose things in the pedals. But you might also find
(as someone said) bent rings causing things to touch the derailleur
cage. I even tracked one difficult click down to a saddle , although
that (or a seatpost noise) is unlikely if it's gear-specific.
Noises on a bike are tricky because it all sounds below you when
you're riding. They're difficult to locate. A helper gets a better
point of view, so to speak, and can also (carefully) feel for slight
motion between mating parts. But having the load in place is
important.
- Frank Krygowski
jobst....@stanfordalumni.org
>> I built a bike to use for duathlons which I dearly love but it has
>> a problem that is driving me crazy. It is a double chain ring, 10
>> speed Ultegra equipped XRP Cion frame road bike. When the chain is
>> on either the smallest cog or the 2nd smallest cog, there is a
>> noticeable clicking noise coming from the area of the front
>> derailleur. It can be heard only when I am pedaling hard. I have
>> had the bike into two different bike shops but no one can correct
>> the problem. The last mechanic told me it was either the frame
>> flexing or the crank flexing or both. If the frame is flexing then
>> I guess I'm SOL (unless I want to replace the frame). If it's the
>> crank then I can do something about that. Is crankflex common or
>> is the likely culprit the frame? The crank is a Ritchey which I
>> chose because it was cheaper and lighter than the Ultegra. I would
>> hate to switch to an Ultegra crank and still have this infernal
>> noise.
> The bike shop responses don't make sense to me. Flex doesn't cause
> noise unless something is loose & shifting, or unless something is
> hitting something else. It sounds to me like they haven't located
> the problem and are just guessing.
If the BB spindle bends and the crank does so too, the CW can wobble
from side to side under pedal loads and cause the chain to drag,
alternately on either side. I did not get that impression from the
question however.
> I've had friends bikes that had (said the shop) supposedly incurable
> noises. The latest one (on an old bike) turned out to be generated
> within the freewheel - but it wasn't a once-per-revolution noise.
> It came and went with maddening randomness. I found it by loading
> the cranks, as described below, and rocking the bike back and forth
> as I sat on it.
Some of that flex can come from the seat tube being too light weight
and the BB yawing to cause chain rub on the front derailleur.
> If your noise is once per revolution, it's probably in the front half
> of the drive train one way or another. I'd get the bike in the
> offending gear, ride to generate the noise, and note the exact crank
> position. Then get into your garage, workshop, or wherever it's
> quiet, and work the bike back and forth through that crank position
> while maintaining strong pressure on the cranks. See if you can
> replicate the noise while not riding, and locate it with a helper.
Check how true the CW runs under no-load.
> I've found clicks from the following: Loose crank bolts; loose crank
> arms at the crank axle attachment; loose bearing cups or bearing
> lock rings; various loose things in the pedals. But you might also
> find (as someone said) bent rings causing things to touch the
> derailleur cage. I even tracked one difficult click down to a
> saddle , although that (or a seatpost noise) is unlikely if it's
> gear-specific.
Clicks are everywhere where there is no lube, bicycles being so highly
stressed at low RPM in the drive train that small elastic movement
occurs at every interface.
> Noises on a bike are tricky because it all sounds below you when
> you're riding. They're difficult to locate. A helper gets a better
> point of view, so to speak, and can also (carefully) feel for slight
> motion between mating parts. But having the load in place is
> important.
Takes time and distance to sort them out.
Jobst Brandt
Crescentius Vespasianus
I had a similar problem, and I re-greased the headset, top and bottom of
head tube, and the click disappeared.
Nick L Plate
> When the chain is on either
> the smallest cog or the 2nd smallest cog, there is a noticeable
> clicking noise coming from the area of the front derailleur. It can be
> heard only when I am pedaling hard.
Swap rear wheel, freewheel movement is transmitted by the chain and
can be heard in the bottom bracket area. I suggest this first because
you may end up chasing your tail if assume it is crankset related.
Check chainring bolts for tightness.
Qui si parla Campagnolo
wrote:
I did too and finally solved it on a warm day when I didn't wear the
jacket that had the big clicking zipper. Sounds can come from
anywhere.
Bruce Gilbert
"Qui si parla Campagnolo" <pe...@vecchios.com> wrote in message
news:99c8d96f-e7d0-4655...@w24g2000prd.googlegroups.com...
I bought a new CO2 inflator that allowed the cartridge to slide a bit inside
of the gun. When I got out of the saddle, it caused the cartridge to rattle
around, sounding much like a crank or headset click. It drove me nuts until
I rode one afternoon without the saddle bag.
Bruce
Frank Krygowski
wrote:
>
> -----------
> I had a similar problem, and I re-greased the headset, top and bottom of
> head tube, and the click disappeared.
Good point! I've had creaks from stems and handlebars too, and those
can occur once per crank rev, only when pedaling hard.
- Frank Krygowski
Qui si parla Campagnolo
'Crankflex' only exists to crank/BB makers and their associated
marketeers. 'Stiffer, Lighter, narrower, better, better'...and also
EXpensive!! To the rider it means as much as putting weight at the hub
rather than the rim..in other words, not much.
Chalo
Square taper spindles flex visibly. I doubt this makes much
difference in riding quality, but it definitely exaggerates front
derailleur chain scrub.
I never noticed how much they did this until the first cartridge BBs
appeared and the flex became much more pronounced. I was working as a
shop wrench at the time. When I test rode the first cartridge BB bike
I had built, I thought it was broken because the crank flexed so
deeply.
BMX cranks with 19mm and 22mm steel spindles are quite a bit less
expensive, and much stiffer, than road or MTB cranks of comparable
quality.
Chalo
Qui si parla Campagnolo
Was the steel spindle twisting? Was the crank arm bending? or did you
see frame flex or perhaps bearing 'flex'. I really doubt you were
twisting the spindle, even at your size.