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FD-6500 - Should Cable Contact Derailleur Body

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FD-6500 - Should Cable Contact Derailleur Body

Old 05-30-23, 09:04 AM
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Originally Posted by Harold74
I replaced the OEM BB last summer with another of the same proportions. I think that the original was Ultegra and the replacement was 105. I'll see if I can find the OEM BB in my parts bin to verify the width.

If I did have a triple BB in there, and that would push the crank outboard as you say, would that not reduce the likelihood of contact rather than increase it?
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.
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Old 05-30-23, 09:11 AM
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Originally Posted by rccardr
My second question is whether you are using the correct BB. DA 7700 was available with two, one for doubles and one for triples. They are identical except for width. If your double is mounted on a triple BB, it would sit further out from the frame than optimal.
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.
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Old 05-30-23, 09:17 AM
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Originally Posted by Kontact
The cable guide under the BB may have two positions for the mounting bolt. See if you can move the cable guide to the left to produce more clearance.
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.

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Old 05-30-23, 09:37 AM
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Originally Posted by rccardr
Next question: how strong is the FD return spring?
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.

Originally Posted by rccardr
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.
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.

Originally Posted by rccardr
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.
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.
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Old 05-30-23, 09:42 AM
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Originally Posted by Harold74
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.
Yeah, that's definitely not how to do it. The limit screws aren't there to help you adjust cable tension.
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Old 05-30-23, 09:54 AM
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Originally Posted by smd4
Yeah, that's definitely not how to do it. The limit screws aren't there to help you adjust cable tension.
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.
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Old 05-30-23, 10:11 AM
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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.
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Old 05-30-23, 10:42 AM
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Originally Posted by 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.
Ah. I was thinking of downtube shifters, and adjusting cable tension (and limit screws) as described by rccardr.
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Old 05-30-23, 10:46 AM
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Originally Posted by smd4
Ah. I was thinking of downtube shifters, and adjusting cable tension (and limit screws) as described by rccardr.
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?
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Old 05-30-23, 11:07 AM
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Originally Posted by 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?
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.
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Old 05-30-23, 11:15 AM
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Alright, I'll give the cable slackening thing a try. Thanks for your help gentlemen.
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Old 06-05-23, 01:20 PM
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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.
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Old 06-05-23, 01:44 PM
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Originally Posted by 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.
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....
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Old 06-19-23, 02:06 PM
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Originally Posted by Crankycrank
...but I do have the STI indexed shifters which may do more to prevent the der from moving to the right when in the small chainring but not sure about that. Shimano's official mounting instructions.
I just bought a Lemond Zurich with this same group set and can confirm that the FD shifts flawlessly with the matching Ultegra brifter.
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Old 06-20-23, 10:34 AM
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Originally Posted by rccardr
no need for the cable to be any tighter than pulling it taught by hand when the lever is in the low position.
I hate any slack, so I always use the derailleur limit screws to remove slack when anchoring the cable.
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Old 06-20-23, 11:22 AM
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Good to know there is no design flaw inherent in the FD.
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Old 06-20-23, 12:31 PM
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Originally Posted by shelbyfv
Good to know there is no design flaw inherent in the FD.
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.
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Old 06-20-23, 08:31 PM
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Originally Posted by 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.
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.
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Old 06-21-23, 09:27 AM
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Originally Posted by rccardr
Please explain the difference in cable routing for STI vs. Down tube shifters once it hits the BB. I’m…intrigued.
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
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Old 06-21-23, 10:19 AM
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Obviously, where the bare cables encounter the bottom bracket guides, there's is no discernable difference in routing.

Both nice bikes, BTW.
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Old 06-21-23, 01:52 PM
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Originally Posted by smd4
Obviously, where the bare cables encounter the bottom bracket guides, there's is no discernable difference in routing.
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.

Originally Posted by smd4
Both nice bikes, BTW.
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.
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Old 06-21-23, 05:01 PM
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Originally Posted by Harold74
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).
You can sort of see that, using the siding as a guide.
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Old 06-21-23, 10:47 PM
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Originally Posted by 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
Heads up... watch for Cracks around the spoke holes in those Bontrager Racelites...
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Old 06-22-23, 06:48 AM
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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.
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Old 06-22-23, 07:15 AM
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Nice bikes. Looks like the LeMond might be a better fit, IMHO. The TI looks too small.
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