I think the Ibis needs a new rear derailleur. Bike has a new chain, cables, OK chainrings, cogs, but won't hold a gear. Plus the chain is falling off the inside of the 39 going up hill, even after a new BB (old BB was whacked, had that replaced recently, crank set was moving laterally). I think this happened on another bike a few years back; a 7800 derailleur with 20,000+ miles exhibited these symptoms. LBS installed a new unit, *poof* she was good as-a-new. The derailleur spring gets tired. Not unlike male potency issues at my age.

Happily I don't suffer from those, but I do wear out these derailleurs. This one has over 20K miles on it too. LBS's don't see this much, most people don't keep their bikes that long or actually put that many miles on the rear gears. But I'm confident this is the culprit on this bike (the Ibis).

If the spring tension on the derailleur is shot, it can't position the chain at the right angles, and these symptoms would be quite consistent with that. Plus the rear adjuster barrel is just about frozen. That component sees a ton of rain/road salt, so it's hardly surprising.

Not that this 7800 rear derailleur owes me anything after nearly 5 years and probably 25K miles.

You can put viagra in your derailleur, but if it gets stuck in a gear for more than a few hours, you have problems.

Don't forget the lubrication.

Glad to hear the old joystick still works, Unc. That's really useful information.

I think I read somewhere around here that once the pivots wear, the der can't hold its position relative to the cog, and you get crappy shifting.

Seems to me the spring can be replaced, but not the pivot rivets and bushings (if there are bushings). Now if you have a 105 transmission like me, it's only about $50 for a new RD. You guys with the Ultegra and DA "bits" (as coasting so quaintly calls them), have to shell out quite a bit more. My point, such as it is, is that if it's just the spring, you should be able to get it replaced for $10 instead of having to come up with $150 or $200 for a new der.

So I think your diagnosis is wrong, old man. You're in the ballpark, but the specifics are all whack.

Good time to make the leap

Nope. New derailleur time. Remember the rear adjuster barrel is also frozen. Ultegra 6700 units are $100 or less. Give or take. That'll work.

It's my rain/snow bike. I just want to get it back on the road.

Nah. Bike is whacked. Time for that new Moto Ti!

The Ibis pisses on any Motobecane Taiwan Ti frame. Trust me on this.

do you know if you're 105 will hold up for 25k miles? If it dies in 10k, it's still more expensive

this is why i eschew riding. i don't want to wear out my bike.

Nobody wears out computer keyboards like Uncle Pcad, either.

hey pcad

this ibis is the bike you will be racing during the coming season right? is this you laying the groundwork for your excuses threads when the time comes?

I honestly don't know. I'm not knocking the weight weenie stuff. I have about 6K on my current 105 RD and it works fine. I'd hope to get 25K miles or better, but I guess that remains to be seen. Obviously, those of us who do a lot of hills are going to wear out drivetrain components like cables, STI shifters and derailers more quickly than flatlanders.

My impression is that the lighter stuff in Shimano's lineup isn't any more durable--just lighter.

Anyway, pcad didn't address my technical observations. Just blew me off. Can you believe that? I suspect he's clueless as to why an RD would fail, so I'm sticking with my pivot slop diagnosis. Not that I know, but I do my own maintenance (and I suspect pcad does more than he lets on), and that's my position on the matter. Again, if it's just the spring, you'd think they'd make it replaceable.

Busted.

Yeah, actually, as a Campy guy I have to hand it to Shimano. For their price, their parts give a good amount of service in crappy conditions before giving up the gun.

But I'd be happy to replace the springs in my record RD when the time comes. I've done it on customers' derailleurs, and it would definitely be awesome if Shimano had the option because it's so cheap and easy.

I'm not replacing the D.A. unit with a 105 unit (God Forbid). I'll only lower myself to Ultegra.







Now go to the Boy's Room, wash your mouth out with soap, and we will never speak of this again.

Does anyone here really think a rear derailleur should last more than 25,000 relatively hard, sloppy, in all manner of unGodly condition miles?

Because I don't.

I blame the derailleur hanger. And Bush.

Cheney. It's always Cheney.

it's probably a combination of weakened spring tension and increased play in the pivot points. if this is a rain bike, wear to the pivoting parts is to be expected. as you said, 25k later, it owes you nada, time for new.

You're a Scientist, so who can argue with your conclusions?

Touché, good point.

We know he was the power behind the power, but it was Bush's watch.

You have a Dura Ace rain bike??