Whew! Yeah… it’s been a while. I write this from a train, because it’s one of the few chances I’ve had to settle down enough to focus on it. I figure however it’s about time to relay an experience I had building up a Calfee Luna last season, an issue actually, and the solution to which I arrived. Some time ago I’d heard of difficulties getting Shimano’s 11-speed Ultegra front derailleur to work optimally, and didn’t quite understand what the problem was. It’s just another derailleur, right? Now that I’ve seen it myself, and not heard of a solution, I find it hard to believe others aren’t occasionally encountering this, so here’s a description of what worked for me.
It’s no secret among those who know me that I have minimal enthusiasm for these component manufacturers each time they release another group with more gears. I was fine with 5 and 6-speed, and really liked 7-speed. When they released 8-speed that would have been okay, but 7 was enough, and the 8-speed system never seemed to perform well. I’d rather have 7 that work great. 9-speed was fabulous, in my opinion. It shifted well, was serviceable, highly compatible with off-road components – allowing us to develop creative gearing solutions for tandems and touring bikes. It was also the first time we saw truly wide ranges available for folks who needed them with minimal compromise to shifting performance. Then they jumped to 10-speed… yawn. The groups got noticeably lighter and stiffer, but the tenth gear didn’t matter much and performance became finicky and less reliable again, and the superior features did not require an additional cog.
Eleven speed appears to be a whole different story. Historically I wouldn’t have cared about that 11th gear, if you can’t tell by now, but properly installed this stuff works brilliantly. The range for a double is wider than the old triples, and the ease, crispness, and response of shifting feel is phenomenal. Even any lack of cross-compatibility (road vs. mountain) is beginning to not matter any longer. The price for this however, aside from monetary cost, is the precision required to get it set up working perfectly. This brings us to the point of today’s post.
After so many years of building bikes using frames from Calfee Design, I had somehow forgotten Calfee build their frames using asymmetric bottom bracket shells. I’ve never seen a mis-aligned Calfee frame, but you can clearly see in the photo that neither the seat-tube nor the down-tube intersect the shell at its center. This is intentional, and perfectly okay as long as the bottom bracket, the wheels, the steering axis, and the saddle’s center are all within the same plane. That is to say the frame must be in alignment, and it is, even though the shell is offset to starboard.
If you understand kinematics you will recognize that the attachment lever and parallelogram on a derailleur have different relative movements throughout their stroke. Although the parallelogram ensures the cage’s stability and vertical orientation, it does move through an arc. Since it’s activated by a cable pulling on a lever, and this cable pulls in an effectively linear fashion (as opposed to unwrapping about a barrel), a given amount of cable pulled at the lever will result in different resulting movement at the cage according to location within its range of travel. Manufacturers account for this by matching the radius of the control’s cable wrapping mechanism to the dimensions of the contact points and parallelogram in the derailleur. SRAM in particular, I believe, takes pride in their 1:1 pull-to-response ratio. That’s cool… but one of the sweetest things about Shimano’s latest 11-speed mechanical system is the fast, smooth, and effortless action of the front mechanism. This is acheived using a much longer lever than in the past, even requiring variable cable anchoring. As brilliantly as it works, properly adjusted, it is unfortunately rather unforgiving to even minor variations in spacing from the seat-tube.
I found on several initial builds that the setup required a bit extra care in getting the adjustment perfect, and there’s the new trim “feature” which disallows the derailleur from slamming all the way to it’s lowest point upon the down-shift, but the results were in general excellent. Trying to finish the build on this Calfee however, no matter what I tried for yaw alignment, cable tension, and limit screw settings, it was simply impossible to get full swing out of the derailleur and it would rub the chain on the big ring. By the time the cage had reached the big ring position, any further cable pull would result in the derailleur moving up more than out, because its mounting point (the seat-tube) was too far away. What do do?
One idea I had was an eccentric clamp spacer, permitting fine adjustment. I still may work on further developing that for similar applications, but I then remembered SRAM makes a Wide Spacing version of their clamp adapter. Their clamps are very light and well made, so far seem reliable, and integrate perfectly with SRAM’s own chain-watcher device – a rather clever design. They are however made to support exactly the profile of SRAM’s own derailleur body, preventing flex and yaw movement. Shimano’s derailleurs don’t rest well against the little tab protruding out from the clamp, so I filed it down to fit the contour, and installed.
Problem solved! It works perfectly and has often become my clamp of choice for many builds other than just Calfee frames, and for non-SRAM mechanisms. Plus we still get the added benefit of using SRAM’s fancy chain-watcher if needed.A couple final notes:
- I must admit I do not remember what the initial clamp adapter was that I tried. It was in all likelihood a Shimano, which I have otherwise found to work well.
- I have installed every edition of Shimano’s Di2 front changers to Calfee frames, more times than I remember. We never experienced this issue, so it appears to only apply in the case of 6800 mechanical. That said, I am curious to explore whether front shifting performance might be further improved this way.
- The FD-6800 uses a yaw-preventing set screw just like the Di2 mechanisms. If the clamp is filed to fit well, this set screw becomes unnecessary.