rccardr 

You are correct. And a 105 BB would have the same dimension as both DA and Ultegra units.
Next question: how strong is the FD return spring? I understand your description of the problem but am having a difficult time understanding why such a mild force - the Bow Effect, as you put it- would be able to move the FD in any amount at all when presented with the force of a healthy return spring.
Additionally, have you considered putting a little more slack in the cable when the lever is in its fully depressed position? No harm to be had there, and it would remove any potential Bow Effect.

Harold74

So the OEM and current bottom brackets are both 109.5 mm wide. I tried to snap a pic on my way out the door for work but my phone died just then.

Harold74

Thanks for your input. The shell has one hole and the guide has two, as you've surmised. Per the photo below, however, I believe that I've gotten it set up optimally for this particular issue. You know, short of running the cable outboard of the damn chainstay.

Harold74

I don't really know how to answer that. I don't know how stiff it is or how stiff it out to be I'm afraid. I'll man handle a few derailleurs when I get home tonight to see if I can get a sense for whether or not the spring in question has gone soft somehow. As you know, springs are freakishly reliable. Just not a lot to go wrong there.

I see your point and sympathize. Anecdotally, I identified the problem -- as I've described it at least -- while riding. Simply put:

1) When there is no contact, the FD lever and FD stay put.
2) When there is contact, the FD lever and FD move to eliminate the contact.

This is what led me to the "bow theory". I am open to the possibility that my theory may be incorrect however.

It has been my experience with downtube, bar end, and thumb shifters of many kinds that the forces at play are actually in a pretty tight balance. That's the only way to produce "light action", right? This is so much the case that all of the shifters in my possession seem to offer differing amounts of resistance to motion with the spring vs against the spring.

I hadn't considered that but I will, now, at your recommendation. I might struggle to love it though as I'm pretty into having my cables taught. It certainly would seem to solve the problem if the bow theory is what's actually happening. A slack cable makes for a pretty lousy bow. I already find my rear brake cable slackness annoying but livable so perhaps I can adapt.

I've been doing the thing where I fasten the cable with a 3rd hand tool and then dial up the limit screw to deliberately get the cable taught. Maybe that's the source of the problem.

smd4

Yeah, that's definitely not how to do it. The limit screws aren't there to help you adjust cable tension.

Harold74

It's a common trick for getting the appropriate cable tension into the system for modern brifter setups, no? This was the only way I could get my wife's Tiagra 10sp setup to shift properly up front.

rccardr 

Well, it’s one way to do it when working with STI’s, which have limited pull variability. When you move ‘em, they click. But friction downtube shifters have bunches of pull variability, so no need for the cable to be any tighter than pulling it taught by hand when the lever is in the low position.

smd4

Ah. I was thinking of downtube shifters, and adjusting cable tension (and limit screws) as described by rccardr.

Harold74

Oh, it is downtube shifters. The STI example is just where I got the idea from.

Realistically, if there were a ton of pre-tension in the FD cable, it would just move the FD to relieve it, right?

smd4

Sure, except doing so will alter the shifting precision, and possibly make the derailleur inoperable. Personally, I only use the limit screws to adjust derailleur travel. I've never used integrated shifters, so I don't know how they're adjusted. But with downtube shifters, after setting the limit screws, then I'd adjust the cable tension using the method rrcardr described earlier (although I'd use needle nose pliers to get a better grip on the cable). And so, in my method, there is no "pre-tension." With the derailleur on the small ring, shift lever all the way forward, I pull the cable taut and snug the binder bolt.

Harold74

Alright, I'll give the cable slackening thing a try. Thanks for your help gentlemen.

Harold74

By coincidence, I did a pre-purchase inspection on a 2002 Lemond Zurich over the weekend. It's got the very same derailleur. And the cable contacts the dust cap thing in the same way. The photo below doesn't show it well but there's a black track mark on the dust cap where the cable touches. This bike is a brifter setup with a fairly taught cable and no discernable ghost shifting problem. This new information doesn't really change anything discussed here. Just another data point for interest's sake.

maddog34

4700 tiagra??? next time, set the Tiagra Ft. Der. with the Tiagra Brifter in the SECOND Click position.... as per Shimano. I own a 4700 Tiagra group... the full instructions are online....

Harold74

I just bought a Lemond Zurich with this same group set and can confirm that the FD shifts flawlessly with the matching Ultegra brifter.

SurferRosa

I hate any slack, so I always use the derailleur limit screws to remove slack when anchoring the cable.

shelbyfv

Good to know there is no design flaw inherent in the FD.

Harold74

Mostly. I'm sure that the derailleur was tested ad nauseum with the companion brifter setup which would, surely, represent the overwhelming majority of setups. Perhaps it was not tested with downtube shifters.

rccardr 

Nah, they. test that stuff to death. Bar ends, too.
Please explain the difference in cable routing for STI vs. Down tube shifters once it hits the BB. I’m…intrigued.

Harold74

Fun. Thanks for your continuing participation on this. I'll describe both setups as "conventional", supply a photo of each, and then let you ask any follow up questions as required.


Ultegra Brifters

Downtube Shifters

smd4

Obviously, where the bare cables encounter the bottom bracket guides, there's is no discernable difference in routing.

Both nice bikes, BTW.

Harold74

That's right. Both bikes route the cable through plastic guides bolted to the underside of the bottom brackets. The cables don't travel through any friction inducing brazings, as is the case with a couple of my older bikes.

Thanks for that. The blue and white Lemond Zurich is new and is something of an experiment in fit. The titanium frame is interesting in that it is both compact and uncommonly long in the effective top tube relative to its other dimensions. As you can see, I had to jump through some hoops to get the fit right for me on the front end. But, now, it fits like a glove. As the two bikes are currently set up, they are of identical size with respect to the relative location of my body/bike interfaces (bars, bottom bracket, seat). I'm hoping that the Zurich can be an equally comfortable ride as the titanium bike but with more conventional proportions. My seat post is probably a little short on the Zurich but that just seems to be the required compromise for me to be able to achieve my preferred reach and stack height. Long arms.

smd4

You can sort of see that, using the siding as a guide.

maddog34

Heads up... watch for Cracks around the spoke holes in those Bontrager Racelites...

rccardr 

If both bikes use the same FD and there's a difference in cable clearance between them, it's due to the difference in BB cable route spacing, not shifter type.

SJX426 

Nice bikes. Looks like the LeMond might be a better fit, IMHO. The TI looks too small.