I am new to this forum., but I've come across threads in Google searches for a while now, one of which was a couple years ago concerning DI2/KI2. Is anyone using this system now, and how is it working for you? I have the Ultegra DI2/KI2 on my Burley, but the front shifting isn't as clean as I would like. I am using a triple crank (with the inner gear removed), what I think is a FSA "triple" clamp (which is supposed to move the deraileur more outboard), and a personal modification to the FD. I find we have to double shift sometimes to get the FD to drop to the lower ring...Thoughts? I'm also looking into fitting a double crank, wanting to set it up so I can swap between standard and compact ringsets. However, I don't think this will "fix" FD smoothness.
Thank you

I usually think of a double shift as a shift in front rings and rear cogs at the same time.

What do you mean by double shift?
What type, brand, and year shifters do you use?
What front derailleur do you use?

Sorry, by double shift I do mean shifting both the front and rear at the same time (to the smaller ring and a smaller cogthe XTR 11-36 is spaced to make these shifts similar to simply shifting to the next larger rear cog). I'm using Ultegra STI 6770 shifters, the FD6770 where I replaced the actuater screw to push the shift farther outboard (with the stock screw the motor won't reach out far enough but the design of the pivot points of the derailure cage itself could reach), and a modified RD 6770 from K-Edge. The shifts to the larger ring are fine, great in fact, but on occasion without the double shift (front and rear) the chain won't drop to the smaller. I'm currently running Ultegra 53/39 rings (and the 36-11 cassette).

Some ideas to try (if you haven't already):

Shift while your cadence is reasonable. Lower cadence generally means more tension on the chain and that hurts shifting. I know this can be difficult. It helps if you can really shift the back and front at the same time. If you get the timing down it works well.

Since you are only running two rings up front, a) install a chain catcher just inside of the inner ring. b) adjust FD and FD inner stop for an aggressive shift to small ring and rely on chain catcher to prevent the chain going inside of the small ring. I used to do this on a cyclocross bike with non indexed left bar end shifter and I could just slam the shifter all the way and the FD cable would go completely slack.

Angle the FD ever so slightly so that the leading edge is inboard of the trailing edge. This helps it guide the chain off the big ring. Just enough so you can barely see it. Too much and you will have more chain rub. Sorry to those that have a braze on FD with no rotational adjustment.

Run a little longer chain. a longer than usual chain length on road bikes will result in a little less chain tension and slightly better shifting to the small ring.

Keep chain very well lubed. Regardless of lube used a well lubed chain slides easier off the big ring.

Change you chain line in a little. - This may not be possible since I think you have external BB bearings, but it is one approach.

My approach is to do most of the above and use 1999-2006 Campy left shifter. Amazing how much more load I can shift under with that shifter. I don't call out shifts to inner ring and my stoker just keeps pedaling right through it. I know this is probably not one you will want to do but it may apply to others.

Good luck - oh and if you want to get electronic shifting then get it. That would work too.

The 6770 series is the electronic, so the Campy shifter isn't an option for me. One of the "company selling points" was that the front derailleur is supposed to perform shifts while under significant pedal force...Single bike users rave over the ability to shift the front while climbing without reducing pedal force. Either way, we've tried this with no success (when the problem is occurring). I don't know if a longer chain would work. It seems that, with all else but chain length being equal, "x" amount of force on the pedals would give "x" tension on the chain between the cog and the rings. Changing the chainline isn't an option for me, but angling the front cage may be. I am running a home-made chain catcher, but the programming/design of the front derailure is supposed to "over-shift" just a bit and then return to proper alignment to better facilitate shifts. It also self-adjusts in relation to the RD position (odd to hear the first few times, but amusing to watch in the repair stand). The double shift works every time as long as my pilot remembers to do it (most of my pilots have at some point double shifted a mechanical setup and dropped the chain...it's a hard habit for them to develop I guess).

Thanks, there are some ideas to try.

Sorry for my mistake. I assumed you had mechanical - well you how assuming goes. You are right Di2's big selling point is front shift perfection. With all the power the electric FD is supposed to have what happens when you have a failed front shift? I guess it just stays in the big ring while rubbing the FD cage a lot making lots and lots of noise?

Just guessing here hopefully someone with more knowledge will chime in:

When in the big ring and small cog is there any extra room between the outside of the chain and the FD cage? If so maybe an adjustment can be made to have less gap there so that when the FD moves the same distance to the inside it ends up further inboard when shifted into the small ring.

It seems to me that the crux of your problem is in the chainline. It sounds like you have an incorrect clamp, which does not put the FD in the right place for your crankset, and you attempt to compensate for this deficiency by swapping the actuator screw. Which is an ingenious solution, but, in addition to moving the cage, it has the effect of altering the trajectory of the cage (angle and horizontal travel) during the shift, and possibly causing your shifting issues.

If that's the case, I'm afraid that the only solution is to get a double crank. A triple with an inner ring removed would require a very long clamp and your odds of finding one aren't good.

Can you report the chainline of your crank and measurements of the position of the FD with regard to the rings with actuator screw reverted to stock?

Co-Motion is using a triple FSA with inter ring removed which led them to produce there own extended derailleur clamp for correct chain line and address shifting problems.

https://bicyclesportshop.files.wordpr...09/image3.jpeg

i am also using DI2 with extender clamp & FD slightly angled in at front, after a lot of trail & error it works great out of the saddle up or down know matter what load you have on chain.

to post #8 .

Also, mind the gap distance btwn the FD outer plate and big ring. Set to ~3mm and no more. Uploading a photo might save some guesswork here.

It is important to use the Di2 FD set screw too, and against a firm backing plate. The Di2 FD clamp from Shimano provides a very good base for the screw to hit. This screw helps augment the FD strength and keeps if from twisting under load.

Chain type shouldn't be an issue here as that typically is a non-factor in FD downshifts.

Yep, that sounds like the correct solution. (Not entirely clear where one would get that custom clamp without buying a whole tandem - but that's for the OP to research.)

I'm sure Co-Motion would be willing to assist:

Co-Motion Cycles, Inc.
4765 Pacific Ave
Eugene, OR 97402
United States
Office: (866) 282-6336

We have had Di2 on our tandem for over a year and about 3000 miles and it shifts flawless. We don't do it often but it will shift either way with both of us standing. We also have it on two singles with the same results, We also have the k edge RD modification. One thing about Di2 is to stay within the design parameters as much as possible and I think your chain line is off. K edge does make a tandem FD clamp that moves the Fd outboard 2.5mm which may help. The new 6800 series FD also has an adjustment mode like the rear derailluer does and new software may allow this with the 6700 series I just haven't explored it yet. We do use a chain catcher on the tandem as a precaution. With it properly adjusted we can use all of the cassette in the big ring and all but the two smallest in the small chainring with out any rubs (50/34) and 11-36 cassette. One more thing is DI2 likes stiff chain rings for optimal shifting. There are only a few choices in cranks that allow you to switch between compact and standard. (Lightning and DaVinci I think only). Praxis makes mid compact 52/36 chainrings for compact cranks so that gives you some options. I think your problems may be a combination of many of the things discussed in the above posts. don't give up as DI2 is awesome for a tandem.

Shifting the up from the 34 to the 50 front ring while standing is quite a accomplishment for the entire system.

Yes the FD comes with a warning label to keep your fingers clear when shifting it truly is impressive how powerful it is

I do have an extended clamp, although I'm guessing the CoMotion clamp is probably a better design as my option was not specific to fitting my FD to my bike, and I think the CM option was a specific design. When my FD was stock and the actuator screw adjusted fully out, the bike would shift to the large ring while in the workstand, but not on the road, my modification was "just enough" to make it work. Being blind, I can't easily get chainline measurements, but the line itself is the same as when I was running mechanical/cable and the triple. I can run through the entire cassette in either ring without chain rub, if that clarifies things. I'm guessing I would need a narrower BB with a double crank to move the chainline (and the FD adjustment) inboard, without being able to see it, that would however be just a guess. As for the angle of the cage, based on my best measurements (bubble levels and measuring angles related to the seatpost), there is no discernible change.The design of the pivots maintains this angle and allows movement far beyond the reach of the stock actuator and motor. As I will mention later, I think changing the yaw (meaning I adjusted the cage nose slightly inboard) seems to have fixed the problem, at least in the trainer under light and moderate loads.

Thank you, rotating the clamp seems to be working, in the trainer at least, so far.

You know how tandems are, always good in the work stand and a different animal on the road good luck with your adjustments!

The screw has a sturdy actuating point with the clamp I'm using. The "new" actuator screw is titanium, and long enough to thread fairly deep into the FD, maybe just slightly )i.e. fractionally) than the original screw in a standard application (this was one of the design parameters of the new screw...longer, stronger, and depth into the unit). Outer cage plate/chain clearance is about 2mm, and while I've considered playing with this adjustment, I'm fearful of messing up the upshifts, the disadvantage of not having a cable is you can't give the FD that little "nudge" if the adjustment isn't quite there.

I know the Shimano "party-line" is not to make modifications, but if you can ever get one of their techs to discuss some of the product modificatrions they do, well, replacing a screw isn't that big of a deal, and after long-term use, if I break it, I won't seek out warranty work.

Thank for your input, very insightful. I've considered the double crank option, but more because, without the triple range, I would like to be able to interchange a standard and compact crank based on expected terrain and pilot strength. as

What I was looking at for the gearing/crank swaps was maybe something along the lines of maybe a FC6700 and FC6750 (hoping I've got those right as now I don't remember specifically) and a R601 (the 601/603 are Shimanos newer tandem cranks, and they had no reason why the front (R601) couldn't be run in the rear with a right arm from a compatible BB design...But while one tech said "probably," another said that "it" would be too wide, and I never could get a reasonable explaination of what exactly "it" was. Again, party-line rhetoric.

Never plan on giving up my DI2, unless Campy EPS comes out with a triple (its my understanding that their top-of-the-line groupset will offer a mechanical triple, so hopefully it is in the works...).

Thanks,

Oh yeah, or the FC 6800... It is again my understanding (and I'll admit I don't understand much), that the 6800 series uses the same bolt diameter for the 50/34, 52/36, and 53/39 rings.