Rear derailleur / chain noise

[horsefarmer]

Picked up this Planet transit cheap at auction. No history but bike looks like it has had little use. apparently one of the last bikes produced by Murray. Shimano SIS rear dir, no front dir.

Rides and shifts fine - except middle gears make a rattle when peddling. To my eye the angle of the jockey wheels looks wierd and I am going to try to add a few links to the chain. Was on a group ride a few weeks ago and was behind a guy with a Murray mtn bike for a ways on a bike path and his bike made the exact same noise.
Anyone have same problem?

 

[SILVERKINGPC]

HF. It is probably multiple issues. 1st, see if the chain is stretched. If it is 1/16" longer than 12" pin to pin, then the chain is stretched. If the chain is stretched, then the cassette is worn out too. Chain length in the middle gears should not affect noise. Now check to make sure the cassette is not loose. Also, take the derailleur pulleys off and clean and re-grease them. Then check the pulley cage alignment for verticality when the bike is standing straight up. It has to be parallel to the cogs. This should help you get it quieted down...skpc

 

[horsefarmer]

Silverkingpc,
Thanks for the tips! I turned bike upside down and pulled chain off sprocket and the freewheel does seem a little more sloppy than 3 spares I have sitting.
Then I noticed the chain was not centered on the rear sprocket on the middle gears and tryin to shift sprockets or at least putting some extra side load on the freewheel. So I adjusted the barrel adjuster on the bottom of the derailleur so the chain is centered on the gear selected and the noise is much reduced!

 

[RustySprockets]

I think you nailed it, HF. Cable stretch/settling is a simple yet often overlooked cause of noise and poor shifting. A quick twist on the barrel adjuster sets the world right again.

 

[horsefarmer]

Not only is that weird noise gone but shifts are must more positive now too!

 

[SILVERKINGPC]

Most excellent HF!!! Good to hear..

 

[Bendix]

A good reminder to check the obvious before tearing into things!

When you hear hoofbeats, think 'horses', not 'zebras'... ;-)

 

[horsefarmer]

I was glad it was a simple fix. I don't have tools to mess with a freewheel... I guess the "take away" lesson (with indexed shifters) is that high and low chain adjustments are set by the stop screws, but the barrel adjuster sets all the other gears.

 

[Chad T]

That's all there is to it. When I set up a new derailleur I set the limit screws then put the chain in the center of the rear cog and tune it with the cable barrel adjuster by ear. Sometimes you have to balance shift action versus noise.

 

[RustySprockets]

My process is essentially the same, except I make the adjustment with everything set to the highest gear. Then, attach the cable and take out all the slack--presto...you're right in the neighborhood. Barrel adjuster does the fine tuning.

When starting on the center cog, there's a good chance you'll set the cable SO tight that the derailleur can no longer reach its outer limit, even when the barrel is twisted all the way in. That's why I focus on outermost cog first and work my way inboard.

 

[Bicycle808]

Just a note, DEFINiTELY adjust cable tension in the "normal" position. For 98% of rear derailers, that'd be the high (smallest/outermost) sprocket on the cluster. Otherwise, you'll be chasing ghosts for far longer as you dial it in.