Source of weird snapping in drivetrain?

I examined a bike with the following symptoms:

Loud snapping noises coming from the drivetrain when force is applied to
the pedals. Snapping sensation can also be felt through the pedals. Noise
is absent when the bike is coasting, but happens in all gears in and out
of the saddle when pedalling.

BB seems fine, no play and no grinding. Pedals also seem fine. Chain is
worn, but not skipping.

My recommendation: BB, cranks, wheel bearings and derailer seem fine.
Problem is probably in the freehub/freewheel mechanism. The best solution
would be to replace the freewheel and the chain, and see if that works.

Agree? Disagree?

Jacobe- Problem is probably in the freehub/freewheel mechanism. The best
solution
would be to replace the freewheel and the chain, and see if that works.

Agree? Disagree? BRBR

Agree with the freehub diagnosis. Examine the chain as well. Is the 'noise'
about every third revolution?

Peter Chisholm
Vecchio's Bicicletteria
1833 Pearl St.
Boulder, CO, 80302
(303)440-3535
http://www.vecchios.com
"Ruote convenzionali costruite eccezionalmente bene"

Jacobe Hazzard wrote:
I examined a bike with the following symptoms:

Loud snapping noises coming from the drivetrain when force is applied to
the pedals. Snapping sensation can also be felt through the pedals. Noise
is absent when the bike is coasting, but happens in all gears in and out
of the saddle when pedalling.

BB seems fine, no play and no grinding. Pedals also seem fine. Chain is
worn, but not skipping.

My recommendation: BB, cranks, wheel bearings and derailer seem fine.
Problem is probably in the freehub/freewheel mechanism. The best solution
would be to replace the freewheel and the chain, and see if that works.

Agree? Disagree?

Are you trying to use a 9 or 10sp chain on 7sp kit? The chain can grip
the sprockets and make a crackling noise as it disengages. I've just
cured a crackly chain on my track bike by replacing it with something
made to better tolerances (both are 1/8" nominal width).

"Jacobe Hazzard" wrote: I examined a bike with the following symptoms:

Loud snapping noises coming from the drivetrain when force is applied to
the pedals. Snapping sensation can also be felt through the pedals.

The best solution
would be to replace the freewheel and the chain, and see if that works.


Start with the chain and see if that does it. Check to chain for a tight link.

Tim

Zog The Undeniable wrote:
Jacobe Hazzard wrote:

I examined a bike with the following symptoms:

Loud snapping noises coming from the drivetrain when force is applied to
the pedals. Snapping sensation can also be felt through the pedals. Noise
is absent when the bike is coasting, but happens in all gears in and out
of the saddle when pedalling.

BB seems fine, no play and no grinding. Pedals also seem fine. Chain is
worn, but not skipping.

My recommendation: BB, cranks, wheel bearings and derailer seem fine.
Problem is probably in the freehub/freewheel mechanism. The best solution
would be to replace the freewheel and the chain, and see if that works.

Agree? Disagree?


Are you trying to use a 9 or 10sp chain on 7sp kit? The chain can grip
the sprockets and make a crackling noise as it disengages. I've just
cured a crackly chain on my track bike by replacing it with something
made to better tolerances (both are 1/8" nominal width).

I agree with Zog. The chain's also easy to test for. Buy a new one (that
best matches your freewheel/cassette) and try it out. If no cure, then
at least you have a chain available for the next time you need to
replace it (probably in less than a year).

Just while we're on it - do you get the noises at a particular point of
the pedals' downstroke, or does it appear related to chain position?

Another thing to check is chainring bolts.

If still no joy, then pls say what equipment is used.

/Robert

"Jacobe Hazzard" wrote in message gers.com...
I examined a bike with the following symptoms:

Loud snapping noises coming from the drivetrain when force is applied to
the pedals. Snapping sensation can also be felt through the pedals. Noise
is absent when the bike is coasting, but happens in all gears in and out
of the saddle when pedalling.

BB seems fine, no play and no grinding. Pedals also seem fine. Chain is
worn, but not skipping.

My recommendation: BB, cranks, wheel bearings and derailer seem fine.
Problem is probably in the freehub/freewheel mechanism. The best solution
would be to replace the freewheel and the chain, and see if that works.

Agree? Disagree?

Hmmm... since it's in all gears, I'd remove the cassette, clean it and
the cassette splines thoroughly, coat the cassette body with grease,
and reassemble. I've had this happen intermittently with Shimano
cog-on-carrier cassettes.

What kind of cassette and hub is this, anyway?

Jeff