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Conference noted::bicycle

Title:	Bicycling
Notice:	Bicycling for Fun
Moderator:	JAMIN::WASSER

Created:	Mon Apr 14 1986
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3214
Total number of notes:	31946

1167.0. "ATB knocking - HELP!" by DELNI::HELMREICH () Tue May 16 1989 18:57

I have a knocking sound _while pedaling_ my ATB....

I have an '89 Panasonic MC 4500 ATB with 120 miles on it.  I have heard
a knocking sound (about 4 knocks per pedal revolution).  At one time
I had crankset knocking, but I tightened the crank bearings, arms, and 
individual chainrings and got rid of that.  So, it is not the crankset.
The sound is not super-loud, but is certainly noticable. 

The noise appears under quite light pedaling, and is somewhat louder under
heavy pedaling; it only happens in certain gears - 19th is the loudest.  (Big
front chainring, middle rear chainwheel.)

The oddest thing is that it sometimes takes 5 miles of riding for this noise
to start.  Needless to say, it is hard to demonstrate it to a bike shop.


What it isn't (I think..):

The chain is well lubed, and I don't think any links are frozen, the crankset
is adjusted, it's not rubbing brakes.   The spokes are tight (new bike, and 
checked by dealer).

What it could be....

Could it be the freewheel in the back?  I have done serious, but careful
off-roading with the bike, so it is "broken in."  It doens't sound destructive,
so I am continuing to ride, while I try and figure out what it is.


I really appreciate any comments....



Steve

T.R	Title	User	Personal Name	Date	Lines
1167.1	Some diagnostic procedures	TALLIS::JBELL	Ceci n'est pas une pipe. \|	`Tue May 16 1989 21:12`	34
	The bicycle only has 120 miles on it. Things are close to settled, but not all the way. Does it always happen at about the same part of the stroke? Is it exactly 4 time per pedal stroke? No matter what gear? If the frequency changes with the gear, then it's in the rear hub, the wheel or the chain. Otherwise it's in the front part of the drive chain. >I had crankset knocking, but I tightened the crank bearings, arms, and >individual chainrings and got rid of that. So, it is not the crankset. Make sure that you didn't overtighten the bottom bracket. How does it feel when you take off the chain and turn the cranks? If you pedal with absolutely no pressure, do you still get it? If so, do this: 1. Stand on the pedals with the crank horizontal 2. Take your weight off you feet and pedal forward 1/2 of a cycle. 3. Suddenly put your weight back on the pedals. If it makes the sound when you do #3, then something is still loose in the cranks, pedals, or bottom bracket. Check that the fixed cup isn't loose. (I've been having that problem.) -Jeff Bell
1167.2	Take it back	VERVE::BUCHANAN	Bat	`Wed May 17 1989 13:46`	3
	If it has only 120 miles then it may be best to just take it back to the shop. Most shops give a free tune-up after about a months worth of riding to take care of the natural things that will happen.
1167.3	More on the knock..	DELNI::HELMREICH		`Wed May 17 1989 14:20`	18
	RE: .2 - I am going to take it back for its 150 mile tuneup, but I'd like to find out for my own sake, and so I can easily reproduce the noise for the shop. Lincoln Guide Service (MA), is most cooperative, and will no doubt find a solution, or keep trying. RE: .1 - About the knock - it usually happens only in certain gears, and the last time I rode it, the knock changed from a steady "4 knock-beat" to a rhythm - "knock-a-te-knock, knock, knock". I haven't been able to isolate it to the crank or the freewheel yet; I'll try some more. This must be the noise from the Twilight Zone - it defies solution! Thanks for the input so far... Steve
1167.4	Oh, no, you've got...	SUSHI::KMACDONALD	Is there life after drywall?	`Wed May 17 1989 18:26`	5
	Sounds like it might be the dreaded "Campy Clunk" (honest!) - a sort of vague random thunk in the BB which is real frustrating to fix and can come and go rather mysteriously. I seem to recall a note from a couple years back discussing (potential)reasons and (potential)fixes for this.... ken
1167.5		DELNI::GRACE	life is unpredictable; eat dessert first	`Thu May 18 1989 12:40`	1
	Steve, is this a knock-knock joke?
1167.6	CAGE AND CRANK	RIPPLE::RIVETTS_DA		`Thu May 18 1989 13:42`	3
	Check to see if the Front Derailleur cage is hitting the crank arm. Easy pedeling might make a soft knock, and under hard pedeling the frame flex would make it worse.