Time to replace rear derailleur?

[jasonification]

Been loving my 7700 Dura Ace setup. however, recently I've notice the chain beginning to sag after a few days. However, with a quick shifting of the rear derailleur, it returns to its taut state. I'm wondering if this is the beginning of the RD spring giving out? Thoughts? Thanks!

[cachagua]

Chain's taut when you ride, and when you get off the bike, but after a few days it sags? And then snaps back when you ride again? Weird.

Does it sag only in one gear position, but when you change to another gear, then it's taut again? Might check the chain length.

You can change the tension of the pivot spring, if it's really too loose. But that's not usually the way derailleurs die... those springs are pretty robust. Does the pivot need lubed?

What happens when you've got the bike in the stand, and spin the rear wheel backwards? Chain goes around smoothly? What happens when you pedal backwards? Anything goes wrong doing either of those, I'd check the cassette body for stickiness...

Anyway, it CAN'T be the derailleur going bad. Why? Because I just bought one of those. They BETTER last forever!

[Peter P.]

I HAVE had Shimano upper pivot springs go bad before, with the resulting chain sag. So it's possible yours is going south as well.

Before you condemn it, you can usually disassemble the upper spring, clean the parts, grease and reassemble.

[oldpotatoe]

I HAVE had Shimano upper pivot springs go bad before, with the resulting chain sag. So it's possible yours is going south as well.

Before you condemn it, you can usually disassemble the upper spring, clean the parts, grease and reassemble.

AND most decent LBS strip rear ders and keep all the internal bits inna box somewhere..so grab a newer set of springs(for upper and lower pivot), clean, lube der and re-assemble.

[Bob Ross]

I HAVE had Shimano upper pivot springs go bad before, with the resulting chain sag.

^^^This. My 10-year-old 7600 RD has been limping by courtesy of some TLC -- in the form of a complete disassembly and through cleaning/lubing -- every ~2 years, but I'm fully prepared for it to completely poop the bed any time now. If it only needs a new spring I'll be happy.

[jasonification]

Thanks for the helpful replies! I took it out for a ride yesterday and the chain tension has remained taut. Finger crossed it just needed to be ridden outside for a bit. If not, I'll disassemble/reassemble it! Thanks again!

[icepick_trotsky]

^^^This. My 10-year-old 7600 RD has been limping by courtesy of some TLC -- in the form of a complete disassembly and through cleaning/lubing -- every ~2 years, but I'm fully prepared for it to completely poop the bed any time now. If it only needs a new spring I'll be happy.

Wasn't DA 7600 a track group only? Or was Shimano sending you secret prototypes back in the day?

[Bob Ross]

Wasn't DA 7600 a track group only? Or was Shimano sending you secret prototypes back in the day?

Er, I dunno. What # is circa 2005 or 2006 DuraAce, same vintage as 6600 Ultegra?