Fixed gear cog noise

protaghiro said:

I just finished building my 1970 Schwinn Suburban fixed gear (42x15).
The chainring, cog, and chain are all new, and are all 1/8". There is a
slight noise coming from the 15 tooth cog when I pedal. I have read
online that some noise is normal when parts are new like this, and that
there is a "breaking in" period. Is this true?

Not really, not in my experience. But I guess that depends on what you
mean by "slight". If the sprocket is a decent one, it should be very
quiet.

Quoted message said:

I am not positive that my chainline is PERFECT, but it is pretty darn
close to it as far as I can tell.

Take a straightedge, such as a good yardstick, and lay it along the
outside edge of the chainring (remove chain). It should just touch the
outside edge of the rear sprocket. If it is more than a few millimeters
off, this would be your problem. Usually, there are things that can be
done to improve chainline.

--

David L. Johnson

__o | "Business!" cried the Ghost. "Mankind was my business. The
_`\(,_ | common welfare was my business; charity, mercy, forbearance,
(_)/ (_) | and benevolence, were, all, my business. The dealings of my
trade were but a drop of water in the comprehensive ocean of my
business!" --Dickens, "A Christmas Carol"

Quoted message said:

I just finished building my 1970 Schwinn Suburban fixed gear (42x15).
The chainring, cog, and chain are all new, and are all 1/8". There is a
slight noise coming from the 15 tooth cog when I pedal. I have read
online that some noise is normal when parts are new like this, and that
there is a "breaking in" period. Is this true?

You probably have your chain pulled a little too tight. You want it
firm, but not super-torqued back. If this is the problem, it's not a
big deal -- try riding it in a bit. The noise will probably go away
with a little wear on the chain.

CC

David L. Johnson said:

Take a straightedge, such as a good yardstick, and lay it along the
outside edge of the chainring (remove chain). It should just touch the
outside edge of the rear sprocket. If it is more than a few millimeters
off, this would be your problem. Usually, there are things that can be
done to improve chainline.

With the straightedge resting on the outside edge of the chainring, the
other end rests on top of the teeth of the cog. So my chainline is off.
Arg. Is this something I can attempt to fix myself? Or do I pay the
LBS. I built the bike this far...

protaghiro said:

I just finished building my 1970 Schwinn Suburban fixed gear (42x15). The
chainring, cog, and chain are all new, and are all 1/8". There is a slight
noise coming from the 15 tooth cog when I pedal. I have read online that
some noise is normal when parts are new like this, and that there is a
"breaking in" period. Is this true?

My single drivetrain makes a bit of noise too as the quite beefy KMC heavy
duty chain engages with the shimano dx sprocket. I thought it odd at
first, but after a few thousand miles the sprockets show no bizarre wear
patterns, so no worries, it's just normal noise from the heavy chain
engaging the sprocket teeth.

Not saying that you don't have a problem, but I wouldn't get sweaty over
it. What kind of chain you got on that bad boy?

maxo said:

Not saying that you don't have a problem, but I wouldn't get sweaty over
it. What kind of chain you got on that bad boy?

Oh, as somebody else mentioned: chain tension is paramount. Too loose
beats too tight. The tension often changes in different parts of the
stroke, you can mitigate this by loosening the stack bolts on the crank a
bit and whacking the chainring in a tight part of the rotation to move the
ring slightly. Or don't bother...

<[email hidden]> wrote: With the straightedge resting on the outside
edge of the chainring, the other end rests on top of the teeth of the cog.
(clip)
^^^^^^^^^^^^^^^
If that small amount of misalignment could cause a problem, then derailleurs
couldn't work. Think about the amount of misalignment in a chain running on
the outside vs the inside of a cog-set. BUT--you don't have a deraileur to
provide slack for the amount of misalignment you have. So, as others have
pointed out, you should either loosen the chain a little, or just wait for
it to wear.

protaghiro said:

David L. Johnson said:

Take a straightedge, such as a good yardstick, and lay it along the
outside edge of the chainring (remove chain). It should just touch the
outside edge of the rear sprocket. If it is more than a few millimeters
off, this would be your problem. Usually, there are things that can be
done to improve chainline.

With the straightedge resting on the outside edge of the chainring, the
other end rests on top of the teeth of the cog. So my chainline is off.

yeah, but not much. You are talking about half the thickness of the
sprocket, 1/16 inch, less than 2mm. You might fix it by taking a washer
from the left side of the rear axle and moving to the right, or just
adding a washer to the right side, but it really is not enough to be a
problem. Besides, you'd have to re-dish the wheel (slightly) if you did
that. Some bottom brackets have adjustable chainlines, so you could maybe
move the right crank in a bit.

Others suggested a too-tight chain. That is also possible as a cause of
your noise.

--

David L. Johnson

__o | You will say Christ saith this and the apostles say this; but
_`\(,_ | what canst thou say? -- George Fox.
(_)/ (_) |

I would be cautious about letting "wear" deal with the noise. Due to the
many moving parts, chains wear relatively quickly. If you have too much
chain wear, then the rings wear to the point that a new chain will not fit
(after what it cost me for new front & rear rings, I took to replacing my
chain annually). Likewise, I suspect that misalignment will cause wear that
you do not want.

Make sure there is some slack in the chain.

Adjust the front & rear ring positions as per the suggestions from others on
this thread.

Make sure the rings are flat (not warped)

Make sure the noise is the chain & rings, and not a wheel bearing, bent /
broken axle, crank clicking on frame, tire rubbing on something, etc. ( I
know these should be obvious, but there is the computer tech support joke:
Customer "My computer will not turn on, there must be something wrong with
the switch." Tech "Ok sir, let's start at the beginning. Is the computer
plugged in?" Customer, screaming "of course it is plugged in, what kind
of stupid" click (hang-up))

Bruce Nelson

<[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I just finished building my 1970 Schwinn Suburban fixed gear (42x15).
The chainring, cog, and chain are all new, and are all 1/8". There is a
slight noise coming from the 15 tooth cog when I pedal. I have read
online that some noise is normal when parts are new like this, and that
there is a "breaking in" period. Is this true?

I am not positive that my chainline is PERFECT, but it is pretty darn
close to it as far as I can tell. Should I be worried about this noise?
The new drivetrain parts have about 1 mile of use. Will the noise
subside with more use on these parts?

note: I posted this in rec.bicycles.tech also... but I don't think any
of them care. Boohoo!