Confusing rubbing

Smmb said:

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Just got back in from a nice ride, with a new "problem". The big ring =
rubs the front derailleur. Kind of normal, but with a twist. This only =
happens every SECOND revolution. I first noticed it while in big/little
= on a 2% incline, while standing. So, I sat. No change. Not each =
revolution, that's the screwy part, each other revolution.
I figured I was compensating - that my unconscious reaction was to let =
up on a downstroke when the previous stroke brought on the noise. Not =
true, as this happened standing, sitting, and after I began to test for
= it, it happened in the smallest cog and the next one, at any RPM and =
pretty much with a variety of pedal pressures.
Checked the chainring bolts, the crank bolts, have not yet looked at the
= BB. Should I just hope that it changes to EVERY revolution, and then =
fix that ?? :-) But every second revolution - this really has me =
staring blankly.
Who can figure this one out ? --=20 Sandy Paris FR
*******
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Maybe something in the chain itself in combination with a slightly bent
chain ring. If the chain abnormality comes around every other revolution
and the chain ring has a slight outward bend; this combination pushes
the chain as far out as it goes. Are you using some kind of chain
joining link? What did you change or what happened before this started
to happen? How many links in the chain and how many teeth in the large
chain ring? ... (106 links and 53 teeth maybe??)

--

SMMB said:

Just got back in from a nice ride, with a new "problem". The big
ring rubs the front derailleur. Kind of normal, but with a twist.
This only happens every SECOND revolution. I first noticed it while
in big/little on a 2% incline, while standing. So, I sat. No
change. Not each revolution, that's the screwy part, each other
revolution.

I figured I was compensating - that my unconscious reaction was to
let up on a downstroke when the previous stroke brought on the noise.
Not true, as this happened standing, sitting, and after I began to
test for it, it happened in the smallest cog and the next one, at any
RPM and pretty much with a variety of pedal pressures.

Checked the chainring bolts, the crank bolts, have not yet looked at
the BB. Should I just hope that it changes to EVERY revolution, and
then fix that ?? :-) But every second revolution - this really has
me staring blankly.

Who can figure this one out ?

My guess: it's the chain's quick-link connection. (My PC-99 is noisier
than its Shimano predecessor.)

Bill "if it was the ring then it would do it every rev" S.

" S o r n i" <[email hidden]> a écrit dans le message de :
news:[email hidden]...

Quoted message said:

SMMB said:

Just got back in from a nice ride, with a new "problem". The big
ring rubs the front derailleur. Kind of normal, but with a twist.
This only happens every SECOND revolution. I first noticed it while
in big/little on a 2% incline, while standing. So, I sat. No
change. Not each revolution, that's the screwy part, each other
revolution.

I figured I was compensating - that my unconscious reaction was to
let up on a downstroke when the previous stroke brought on the noise.
Not true, as this happened standing, sitting, and after I began to
test for it, it happened in the smallest cog and the next one, at any
RPM and pretty much with a variety of pedal pressures.

Checked the chainring bolts, the crank bolts, have not yet looked at
the BB. Should I just hope that it changes to EVERY revolution, and
then fix that ?? :-) But every second revolution - this really has
me staring blankly.

Who can figure this one out ?

My guess: it's the chain's quick-link connection. (My PC-99 is noisier
than its Shimano predecessor.)

Bill "if it was the ring then it would do it every rev" S.

OOOOOHH!! Yeah ! The period is about right, I see !
Just one thing - no quick link on my C9 chain....
But it could well be an ugly link.
Thanks.
--
Bonne route,

Sandy
Paris FR

SMMB said:

" S o r n i" <[email hidden]> a écrit dans le message de :
news:[email hidden]...

Quoted message said:

SMMB said:

Just got back in from a nice ride, with a new "problem". The big
ring rubs the front derailleur. Kind of normal, but with a twist.
This only happens every SECOND revolution. {snip}

Quoted message said:

Quoted message said:

My guess: it's the chain's quick-link connection. (My PC-99 is
noisier than its Shimano predecessor.)

Bill "if it was the ring then it would do it every rev" S.

OOOOOHH!! Yeah ! The period is about right, I see !
Just one thing - no quick link on my C9 chain....
But it could well be an ugly link.
Thanks.

Right. Run the chain between your thumb and forefinger, and see if there's
a protruding rivet (probably where you joined the chain). Also check for a
stiff link, although that would usually cause a rear derailleur blip more
than a front tic. (Love it when I try to sound techie!)

Bill "need to fire MY mechanic (me)" S.

SMMB said:

Just got back in from a nice ride, with a new "problem". The big ring
rubs the front derailleur. Kind of normal, but with a twist. This only
happens every SECOND revolution. I first noticed it while in big/little
on a 2% incline, while standing. So, I sat. No change. Not each
revolution, that's the screwy part, each other revolution.

-snip-

That may be a damaged chain link, whose plate passes the
front changer not in sync with pedal rpm.

Sight your chain from one end and pedal a full chain
revolution. I any link is different fromthe others
investigate that asap . Chain failure is serious.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971