Bicycle Mechanics - Rattle type sound from rear derailler area.
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Whenever I have the bike a gear combination that has the lower jockey wheel either below or in front (towards the front of the bike) of the upper one, I hear this rattling type sound. It sounds as if it is coming from that lower jockey wheel, but I can't be 100%. I can move that wheel (in fact, I can move them both) from side to side slightly, meaning that they wobble in my hands given some force. So, is this wobbling likely to be causing this rattling type sound? How do I stop them from being wobbly (I'm sure its not good to have wobbly anything)?
05-25-03, 09:37 PM
The upper one should have a small amount of play in it. The lower should not, but usually it is not a real problem. If you have a little clatter then the most likely culprit is a twisted cage or hanger. In certian gears at certian tension, the chain will be trying to ride off the pulley and a worn pulley, sloppy, will make it worse. Tooth wear can also cause this problem, try and compare to a new pulley.
05-27-03, 03:10 PM
Are you sure the sound isn't coming from the upper pulley? If the derailluer is improperly adjusted, the chain can be forced between the upper pulley and the cog, creating a rattlying noise. You use a screw set apart from the high and low to adjust for this. I think it is referred to as a the "B" screw. Are you sure the hanger/derailleur isn't bent?
I am not really sure where the sound is coming from. I can't be sure; its really hard to tell. I'll try the B-Screw thing. I really do not think that the hanger is bent, the bike has never undergone a trauma that would probably create this and it doesn't look bent either.
Alright, after much investigating (about 2 hours now) I think I have finally found the source (about 90% confidence). The rattle sound seems to be coming from the chain rubbing against the right hand side (looking from behind) of the metal cage holding the bottom jockey wheel. Does this sound reaonsable? Is there anything I can do to fix it?
05-27-03, 09:31 PM
This is not going to sound professional, but, grab it at the pulley bolt with a pair of channel locks and tweek it in line. This is only if nothing else is bent, such as the hanger
I'm not quite sure what you mean, Rev. Chuck. What are channel locks and what exactly am I doing? This sounds like the kind of process that is irreversable if I screw it up. What is the goal here, to bend the hander away from the pulley (I just took a good look, the hanger is not bent at all, which kinda leaves me perplexed as to why this is a recent problem)? or am I trying to actually turn the pulley or what? I'm just not clear as to what you mean.
05-27-03, 09:54 PM
Channel locks are the large pliers with several grooves in the arm interface to allow different jaw widths. They are also called pipe pliers and waterpump pliers.
I think your problem might be a worn pulley, because you say there are no other issues, like a crash, that would affect the der. You should compare it to a new pulley to make sure.
If the pulley is not worn and the chain touches the cage, then what you need to do is twist the lower part of the cage to get it more in line with the chain line. So you grab it with a pliers to get enough leverage to twist it. This is not a big deal, you are not wringing it off, just twisting it a bit, a little at a time, to get the rubbing to stop.
Your problem, if it has recently developed, is either the result of wear or something getting bent. The wear can also be at the pivot point where the der. bolts into the hanger.
I think that the pulley is fairly worn and that is likely to be the problem. However I pulled the screw (8mm spanner) that holds it in place and took the pulley out to look at it. When I put it back in the rattling had disappeared. Is it possible that the pulley was just out of alighnment or is there another explaination?
P.S. Rev. Chuck, thanks for consistently good advice!
06-02-03, 09:01 PM
I don't think that pulley can get out of alignment other than wear or the bolt being loose. You may have jostled things around enough to get it to quit for a while. Or, did you clean all the grunge off the pulley? If you use a wax based lube it might have built up enough to get the chain to wobble around.
P.S. Thanks, one of my favorite thing to do is try and figure out the answer to these questions.
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