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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 09-17-11, 06:53 PM   #1
Zrane
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Think my derailer needs adjustment?

I just had some fenders put on my bike, and the tires replaced. Since I got it back, my rear derailer isn't shifting right. It's fine on the small chain rings, but as I move up, it gets finickier and finickier. The 4th chainring is where it gets weird. Shifts slowly, and as I go up, the derailer bounces like the chain isn't completely seated, and sometimes bounces back and forth between rings a time or two. Once I try to shift it to the largest ring the chain never completely seats onto the teeth and bounces back and forth between them.

I read the Sheldon Brown article on adjustment, but I'm not entirely sure if I need to be looking at the indexing adjustment or the angle adjustment. I checked to make sure the hanger wasn't bent, and everything appears to be in order to my untrained eye. I do know they had to fit a funky spacer onto the back front derailer to make the fenders fit(The shop was cussing Cannondale a lot, apparently) but the front gears shift fine, and I can't tell if the angle of the chain as been altered.

While I could take it back to the shop and make them fix it, I would rather figure it out on my own because A)They're a bit slow and B)I ride to work on this sucker, and they aren't open tomorrow.

If it matters, the rear derailer is a Shimano Altus, the cogs are Sunrace CSM668, 11-32, 8 Speed and the shifters are Shimano Aceras(According to the Cannondale site).

Any advice would be appreciated!
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Old 09-17-11, 08:33 PM   #2
Don in Austin
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How old is the derailleur? The Altus is not a top of the line unit in any case. If it has wobbly loose hinges it will do what you describe. Also the "B" adjustment should be set
to place the jockey wheel as close to the cassette as possible without it actually rubbing.

Don in Austin
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Old 09-17-11, 08:41 PM   #3
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"they had to fit a funky spacer onto the back front derailer to make the fenders fit" Huh? Can you clarify what they actually did? Did it shift OK before the work was performed?
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Old 09-17-11, 08:42 PM   #4
Zrane
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Originally Posted by Don in Austin View Post
How old is the derailleur? The Altus is not a top of the line unit in any case. If it has wobbly loose hinges it will do what you describe. Also the "B" adjustment should be set
to place the jockey wheel as close to the cassette as possible without it actually rubbing.

Don in Austin
About a month and half old, came with the bike when I purchased it. Roughly 200 miles on the whole thing.

I'll check the B adjustment. Anyway the hinges can be fixed if they are the cause? Or is that a replacement deraileur?
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Old 09-17-11, 08:45 PM   #5
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Originally Posted by dsbrantjr View Post
"they had to fit a funky spacer onto the back front derailer to make the fenders fit" Huh? Can you clarify what they actually did? Did it shift OK before the work was performed?
It did. As it was explained to me, the fender wanted to rub against the front deraileur as the frame didn't leave enough room. They placed a spacer(something they finagled in the shop) to keep the fender from pressing against the front deraileur. I think I explained poorly, and it's actually attached to the frame right next to the deraileur to keep the fender from touching the deraileur. I can provide pictures if need be.
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Old 09-18-11, 11:52 AM   #6
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Thanks Don, it was a combination of the b adjustment being a bit off and the cable being a bit over tensioned. Appreciate the advice.
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