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Old 02-25-06, 10:51 AM   #1
Coyote2
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Hi all. Let me try to explain this. My RD shifts promptly from the smallest cog on up to the larger ones, but sometimes it seems to shift just a tad too far and the chain rattles; when this happens, I can hit the smaller lever (on my Shimano brifter) as if I am shifting back down to a smaller cog, the RD will move a bit and the rattling will stop (but I am still in the same gear). I have tried fiddling with the barrel adjuster, but to no avail.

Any advice on the appropriate adjustment? Or do I just need a lighter touch with the brifter lever to shift just one cog at a time? Thanks in advance.

PS: with a barrel adjuster, which direction is clockwise and which is counterclockwise? Do I judge this while looking at the adjuster from the front of the bike or looking from the back of the bike?
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Old 02-25-06, 11:52 AM   #2
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Picture the barrel adjuster as a simple screw that threads into something (derailleur, shifter, etc.). So for the adjuster on the rear derailleur, look at it from the rear of the bike. Clockwise rotation will decrease cable tension, counter-clockwise rotation increases it.

In your case, it sounds like your cable tension is set too high. Turn the barrel adjuster clockwise 1/2 turn or so at a time and see if that helps. Cable tension should be as tight as possible while still allowing smooth upshifts (to smaller cogs).
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Old 02-25-06, 12:00 PM   #3
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It sounds like you have a Shimano index system with a rapidfire shift set on the bars. I believe that you just have to make some small adjustments of the shifter tension using either the rear derailleur adjustment barrel or , if you have it, another adjusting barrel on the shift lever. Looking from the back of the bike towards the front, as you turn the rear derailleur adjusting barrel counter-clockwise you are applying more tension to the cable. I would suggest that you shift the chain to the smallest rear cog first. Shift up to the second cog . Turn the rear derailleur adjustment barrel counter-clockwise until the rear derailleur starts making noise as if it is going to move into the third cog, then back off till it is quiet. The index system is all based on adjustment off of the second cog. There is also the possibility that the rear derailleur is sitting too close to the entire freewheel. If so, there is a long adjustment screw in the back end of the rear derailleur that , by turning it clockwise, moves the entire derailleur farther away from the individual freewheel cogs. I think that the adjustment barrel moves should solve your problem.
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Old 02-25-06, 03:06 PM   #4
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These seem like very thorough answers, and additionally the two senior members are in agreement. I will follow your advice. Thanks a whole bunch!
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