Help! RD doesn't take up chain slack!

[Bob Ross]

This problem just started appearing with my 7-year-old Ultegra 6700 rear derailler:

The entire RD assembly no longer swings all the way rearward to take up the chain slack when I shift towards smaller cogs.

It seems to be most prevalent when I'm in the small chainring, to the point where I can't use the 5 smallest cogs or the chain goes too slack to shift and often too slack to engage the drivetrain & propel the bike forward reliably.

It's less of an issue when I'm in the big chainring, but still causes skipping and misshifting in those smaller cogs.

Thinking the problem might be dirt/gunk impeding the return spring -- I'm just presuming there is a "return spring" that controls this aspect of an RD's function, hell if I know -- I removed the RD from the bike and gave it a good soaking/cleaning with Simple Green, followed by a liberal dousing with WD-40. That seemed to cure the misbehavior for one or two rides, but now it's happening again.

So...what's going on, and what's the cure?

Looking at an exploded parts view here I gather that coily spring that's part of the "B-Axle Assembly" could be the culprit? Is that something my LBS can easily replace? Is that something I can buy at my LBS and replace myself? Is there some other part or sub-assembly that's more likely the culprit? Or is my entire RD shot, in need of replacement?

Thanks.

[Cicli]

Just get a new derailuer. Its fixable but may not be worth it.
10 speed stuff is affordable.

[bikinchris]

Yes, a good mechanic can repair a rear deraillier with a loose B spring and can even turn that tension higher. But the spring #6 on your diagram does most of the work of pulling the chain tension. That spring can also be turned tighter.
Are you sure your chain isn't just too long?

[Ken Robb]

BTW, WD-40 isn't a very good LUBRICANT. That's not its intended use.

[Bob Ross]

Originally Posted by Ken Robb

BTW, WD-40 isn't a very good LUBRICANT. That's not its intended use.

Yes, I was using it as a water displacer after the soak in Simple Green.

[pbarry]

Maybe disassemble the pivot and spring assembly. Degrease, dry, relube and reassemble. See if that helps. Yes, you can replace the spring yourself. The LBS may even have a new spring or a donor RD they can rob.

[peanutgallery]

Don't be cheap - buy a new one, current one owes you nothing after 7 years. That's a good life

[asiantrick]

I would advice you to buy a new one. Not worth fixing something that's over 7 years old.

[JWDR]

Originally Posted by asiantrick

Not worth fixing something that's over 7 years old.

I would say this is the worst advice I've seen on Paceline.

[oldpotatoe]

Originally Posted by Bob Ross

This problem just started appearing with my 7-year-old Ultegra 6700 rear derailler:

The entire RD assembly no longer swings all the way rearward to take up the chain slack when I shift towards smaller cogs.

It seems to be most prevalent when I'm in the small chainring, to the point where I can't use the 5 smallest cogs or the chain goes too slack to shift and often too slack to engage the drivetrain & propel the bike forward reliably.

It's less of an issue when I'm in the big chainring, but still causes skipping and misshifting in those smaller cogs.

Thinking the problem might be dirt/gunk impeding the return spring -- I'm just presuming there is a "return spring" that controls this aspect of an RD's function, hell if I know -- I removed the RD from the bike and gave it a good soaking/cleaning with Simple Green, followed by a liberal dousing with WD-40. That seemed to cure the misbehavior for one or two rides, but now it's happening again.

So...what's going on, and what's the cure?

Looking at an exploded parts view here I gather that coily spring that's part of the "B-Axle Assembly" could be the culprit? Is that something my LBS can easily replace? Is that something I can buy at my LBS and replace myself? Is there some other part or sub-assembly that's more likely the culprit? Or is my entire RD shot, in need of replacement?

Thanks.

If it's just gunk, take it apart, clean, lube..maybe move the end of the spring to a 'tighter' hole. The suggestions to just replace the thing..geeez, what's happened to good old wrenching on stuff like this... Take it apart, clean, lube...not hard.

[weisan]

Originally Posted by oldpotatoe

If it's just gunk, take it apart, clean, lube..maybe move the end of the spring to a 'tighter' hole. The suggestions to just replace the thing..geeez, what's happened to good old wrenching on stuff like this...

throw-away culture.

[Pierre]

This is likely your issue.

https://www.youtube.com/watch?v=bgiNuJNynMc

Love this guy - very pragmatic solutions for bike part fixes.

[charliedid]

Originally Posted by Pierre

This is likely your issue.

https://www.youtube.com/watch?v=bgiNuJNynMc

Love this guy - very pragmatic solutions for bike part fixes.

He sure loves solvent but seems allergic to grease. Might have been his problem all along since his last overhaul :-)

[Fatty]

Originally Posted by peanutgallery

Don't be cheap - buy a new one, current one owes you nothing after 7 years. That's a good life

7 years old is just getting broken in. Give another blast with the WD and blow that out with compressed air if you have access to it , then a good shot of oil should free it up.

[FlashUNC]

Originally Posted by weisan

throw-away culture.

I have a hard time blaming the advice when Shimano makes it impossible to rebuild and service, for example, their shifters.

And yeah, if the RD has had seven years of hard living and is clapped out, might be time for a new one.