Dear Lennard,
I have a new bike for 2015 and put a new Dura Ace 9000 group on it. During the initial front derailleur setup, I noticed that the plastic guide provided with the front derailleur, which shows which side the cable routing nut should be positioned, indicated the cable to be virtually straight down the center-line rather than one side or the other. I chose the side that it seemed to be leaning to and attempted to finish setting up my derailleur.
The problem that I discovered was that without enough of angle on the cable in relation to the derailleur lever arm and pivot point, the cable has almost zero leverage [see photos 1 and 2]. I played with it for a long time before taking the bike to my local shop to see if they had a solution. I was told by the mechanics that for some bikes (not just mine), the cable exits below the bottom bracket inline with the front derailleur pivot and pinch bolt, thus negating any leverage when trying to actuate the shifter. It also makes tuning the upper and lower trim settings virtually impossible because the cable tension has almost no intermediate points in the lever travel.
From a riding perspective it feels like I need to apply an extreme amount of pressure to the shifter to get it started moving, and then as soon as any lever arm angle is achieved, “WHOOSH,” the derailleur flies into the big ring because I am pressing so hard to get it started.
It is a Dura-Ace 9000 front derailleur, shifters, and chain. The crankset is a Quarq Riken. The chain movement is not a problem; it goes from small to big and back seamlessly. The “feel” of the shift is terrible, as I described before. I have attached a photo of it [photo 1]. I also attached a marked-up photo [photo 2], trying to better illustrate [the problem]. From what I can tell, the point at which the cable exits the bottom bracket shell is determining the cable angle, which cannot be changed.
Do you know of any solution to my problem? Is this simply a design flaw in certain bikes?
― Brian
Dear readers,
Brian sent me the first two photos along with this question. It is a very good question, and I want to explain it thoroughly, because Shimano 11-speed front derailleurs behave differently than traditional front derailleurs. Brian and I went back and forth a bit about this, so I’ll share some of that thread and how he solved the problem.
I think there are a number of people out there who are confused about the use and purpose of the Shimano TL-FD90 and TL-FD68 setup tools — the “plastic guide” Brian referred to. These tools are for setting up Shimano 11-speed front derailleurs, which feature a long, vertical, cable attachment arm. The TL-FD90 tool — probably the one Brian was using — only works with Dura-Ace 9000 front derailleurs and requires removing the cable-fixing bolt. The TL-FD68 works on Ultegra, 105, and Dura-Ace front derailleurs or FD-6800, FD-5800, and FD-9000, respectively. Its top prong will fit into the head of the cable-fixing bolt, so it doesn’t require removing the bolt. This means that it can also be installed after the cable has been connected.
Since front derailleur setup tools are new, it is natural for people to have some resistance to them, since people have never been asked to use such a tool with other derailleurs. With these vertical-arm derailleurs, however, the setup tool provides a useful way of idealizing the front derailleur performance. In Brian’s case, however, due to the location of the exit point of his front derailleur cable from his frame, using the tool and following Shimano’s setup instructions was insufficient to get his derailleur to work properly.
I suggested to Brian, in contrast to the instruction manual, that he run the cable over the top of the bolt from the left to maximize initial leverage. That solved his problem, and he replied this way:
“From the Shimano installation manual, this [see photo 3] is the routing I used (circled). That [suggestion of routing the cable over the top of the bolt] totally makes sense, but I had not tried that, as the Shimano directions are very specific about the cable routing.”
“I tried swapping the ‘converter’ to the other pin and routing over the top of the pinch bolt. The trim settings functioned immediately, but I was unable to get enough cable pull to shift from small ring to big.
“I then thought to use a spot in between your suggestion and the Shimano suggested routing by still sending the cable over the top, but removing the thickness of the converter and allowing the cable to rest directly on the inner pin. I frayed the cable in the process due to my own clumsiness, but the routing shown in photo 4 seems to be providing a good compromise of adequate derailleur throw, trim functionality, and smoothness of shifting action. Garage tests only so far, but thank you again for all the help. It’s frustrating to have problems with a shiny new bike purchased with hard-earned cash. Hopefully my 9000 group works as well over the next two years as the one in your Stress Test.”
I believe that Brian must not have installed the TL-FD90 tool properly, because with the far-right cable exit point his frame has, the cable should have lined up way to the right of the tool’s inscribed line, not “virtually straight down the center-line” of the tool.
Nick Murdick, Shimano’s lead technical instructor, wrote “He can’t have both a cable angle problem and have the cable line up perfectly with the line on the tool. Those don’t go together. I’m suspecting that he did not put the derailleur in the measurement position before taking a reading from the TL-FD90 tool. He may well have other problems, but if the cable really lined up on the line he would definitely not have the problem he is describing.”
I have an Ultegra 11-speed front derailleur with which the cable definitely does line up right on the tool’s inscribed line. But my bike (a titanium travel bike) has a normal Shimano bolt-on cable guide under the bottom bracket shell, which causes the cable to come up from far to the left of where Brian’s cable comes out of his frame.
As for tossing out the instructions and just routing the cable over the top of the bolt, Murdick says this, “Intentionally routing the cable incorrectly through the derailleur should be a last resort. I’ve heard plenty of mechanics say they have similar tricks for derailleurs that don’t seem to want to cooperate. I’ve then worked on some of these bikes myself and was able to undo the hack and set it up correctly and get great performance.
“I teach 11-speed front derailleur set-up twice a week as part of our Shimano TEC classes. While I’m not going to outline the entire class, one of the main points is that you want to run as much cable tension as humanly possible. Always start there. The chain should just barely clear the inner cage plate when riding in the big-big gear combination (trimmed to the inner position on the big ring of course). That’s your indication that you have as much cable tension as possible.
“If there is a chain line issue, or chain stay length issue, or an incompatible crank is used, the front derailleur may not hit the properly-adjusted low limit screw when the cable tension is as high as possible. Luckily, those derailleurs have a very wide range of adjustment and you can simply lower the cable tension until the derailleur does reach the low limit screw. This is our new indication of maximum cable tension for a problem bike. It’s always impossible to get the correct amount of cable tension by setting the low limit screw and then pulling the cable tight with your fingers while you clamp it in place, unless you then increase the cable tension with a barrel adjuster.
“I would be surprised if this wasn’t one of these problem bikes because it’s a PF30 bottom bracket with a ‘who-knows-what’ chain line, someone else’s chainrings that could sit too close together because they aren’t Shimano 3D 11-speed road design, and that bike has a 405mm chain stay, which is right at our minimum requirement.”
“There’s still a 50/50 chance that he simply has the mode converter setting wrong. So I would definitely start there. This whole thing could be solved by simply making sure the washer is rotated to the right place.”
Once the low limit screw has been set, the starting angle of the front derailleur arm when the chain is on the small chainring is determined by the lateral position of the derailleur’s mount off of the frame’s centerline relative to the crank’s chain line. Brian’s is a bike that has the cable exiting so far to the right on the bottom bracket relative to the position of the front derailleur that the initial leverage on the derailleur arm is just too low in either of the Shimano-recommended cable configurations for easy shifting. Routing the cable over the top of the bolt from the left moves its path far enough to the left that it now has enough leverage to actuate the derailleur without the excessive force that Brian was experiencing. Of course, once the cable has pulled the arm even a little bit to the left, the leverage goes up very quickly, and the shift happens snappily.
Shimano must have had a reason for making the derailleur arm vertical so that the cable pulling down on it will have very little leverage (see photo 5). The company easily could have angled the arm to the left, like derailleurs have been for decades, albeit with a shorter arm length, and any cable-pull angle from under the bottom bracket would easily started actuating it. I believe that Shimano chose a more vertical arm and minimal initial leverage in order to increase the initiation force of the derailleur movement. Since it takes more push to get it started, the hand is already pushing hard and fast when the arm has swung left to the point that the cable has very high leverage (see photo 10). This makes the shift very fast. If the arm had instead been set up with high initial leverage, then the hand wouldn’t push as hard to overcome initial resistance, and the shift would be less snappy.
The setup tool is Shimano’s way of providing just enough leverage to keep the actuation force high, but not so high that the user has to struggle to get it started, as Brian’s required before you finally deviated from the Shimano-recommended setup.
The fact that the cable is pulling down so close to in line with the derailleur arm on these 11-speed derailleurs, followed by a fast shift with tremendous leverage on the long arm, means that the stress on the derailleur mount is also higher than with traditional derailleurs. This is the reason that Shimano has a support bolt for braze-on versions of these derailleurs, like on Di2 front derailleurs.
The band-clamp style derailleur (photo 5) provides sufficient stiffness without further support. However, the high cable forces can flex many frame mounts. To counteract this, Shimano braces its braze-on-type long-arm front derailleur with an extra support bolt (photos 1, 2, and 4) that pushes against the frame, but this support bolt could dent, crack, or bore into the seat tube were it not for the (included) aluminum self-adhesive backing plate placed under its tip. This is the same as with Di2, which also has tremendous shifting force.
Since I write bike maintenance books, I have written instructions for setting up one of these derailleurs using the setup tool. Here are the ones relevant to this discussion:
1. Pull the cable up and into the slit in the plastic nub atop the TL-FD68 (or TL-FD90) tool as in photo #8. See which side of the line on the tool it lines up on. If it aligns pretty much along the line, just leave the derailleur as is and skip to step 3. If the cable lines up definitively on one side or the other of the line, check that the configuration of the “converter” at the cable-fixing bolt matches the illustration on the tool corresponding to the side of the line your cable is lined up on. If it does, skip to step 3; if it doesn’t, continue with step 2.
2. If needed, switch the converter. On Ultegra and 105 derailleurs (FD-6800 and 5800), push out the little rectangular converter plate just below the cable-fixing bolt with a 2mm hex key from its recess in the arm. Rotate it 180 degrees, and then push it back into the recess; its protruding pin will now have been moved to the opposite side of the converter plate. On Dura-Ace FD-9000 derailleurs, rotate the notched washer under the cable-fixing bolt so that its notch surrounds the other one of the two protrusions on the derailleur arm.
3. Pull the cable tight under the cable-fixing bolt. Make sure it enters and exits under the bolt correctly: on Ultegra and 105 (FD-6800 and 5800), the cable will enter on the left side of the converter pin, go around the right side of the bolt, and come straight up from there (see photo #5); on Dura-Ace FD-9000, no matter which protrusion the converter notch is surrounding, the cable will enter between the two protrusions, go around the right side of the bolt, and come straight up from there (see photo #1).
4. Tighten the cable-fixing bolt. Tightening torque is 6-7Nm.
5. Set the limit screws and cable tension. Set these like any other cable-actuated front derailleur, with the following exceptions. 1.) When checking for chain rub on the inner cage plate in the lowest (small front/big rear) gear combination, make sure that the front derailleur is in its most inward (low trim) position by activating the inner shift lever three times; adjust cable tension or the inner limit screw to get 0-0.5mm clearance in this combination. 2.) Fine-tune cable tension by shifting to the big/big combination and then giving the inner shift lever a soft click to move the derailleur to the high trim position. Check that the inner cage plate just barely clears the chain (see photo #7) without rub (0-0.5mm clearance), and tighten or loosen the cable accordingly to achieve it. To work correctly, these derailleurs need to have the maximum possible cable tension, and this step ensures that. If, after setting this, the derailleur will not drop all of the way to the inner limit screw (and hence will rub the chain in the lowest gear combination), reduce cable tension just enough for it to barely reach the inner limit screw.
There. That should answer that question!
― Lennard
The post Technical FAQ: Shimano 11-speed front derailleur cable setup appeared first on VeloNews.com.
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