merlinextraligh

Finalizing the specs on a new Calfee Dragonfly. Group is going to be Dura Ace Di2, with the exception of an Ultegra 6870 GS rear derailuer.

The reason for the Ultegra RD is to get a larger rear cog capability. My question is whether to go with the K edge long cage modification, which takes the capacity from a 32 maximum rear cog to 36 max.

For context, we're going to set the bike up with 2 swappable gearing arrangements. Normal setup for flat to rolling terrain will be 53/39 with an 11-25. The mountain setup will be a 50/34 (interchangeable Lightning spider) with either an 11-32, or an 11-36. The 36 would be nice to have for really hard climbs, but we don't absolutely need it.

So the question becomes whether the long cage retrofit will hurt the crispness, speed,or accuracy of the shifting. If so, we'll skip the retrofit, if not we'll get it to add flexibility.

twocicle

From all reports, the K-Edge mod has no detrimental effect on shifting. Mark (akexpress) can chime in here regarding the K-Edge. It may also be on our future to-do list, should we opt for the Lightning cranks and a compact (or super-compact 52/34) setup. I really do like the Praxis rings now on my single (better shifting than Shimano 9000 IMO), so I would try mixing their 52 with a 34 chainring to stretch the range. We have had zero issues with the 11spd Di2 shifting combined with a set of 48/30 Stronglight rings.

On our current Calfee, the Ultegra Di2 RD (6870) "mid-cage" GS handles a 11-32 cassette very well, and that is within spec. However it does seem to be near at the limit for cog size as the B-screw did need to be used to move the top jockey wheel back to clear the 32t cog. In the default setup, I can't see this RD clearing anything bigger without some form of modification like the K-Edge cage.

akexpress 

If you want all Dura Ace get the Dura Ace rear derailleur and retrofit the K-edge cage. We are now using our K edge on a new Ultegra 6870 11 speed with an 11-36 rear cassette and 50/34 Praxis Chainrings. We just competed a supported tour down the Mississippi and road about 400 miles and at the shifting was flawless as it was on the previous 10 speed version. I may try a 52/34 however we never really missed the 52. We are not racers but always rode with the fast group on the ride and did our share of pulls on a fast 6 team pace line and never felt under geared. In fact we many times ended up front on long gradual declines as I think our new Zipp wheels are really fast and aero. Never missed a shift and can completely cross chain when on the big ring and lose only the two smallest when on the 34 as the praxis rings will try to shift up with the slightest drag on them. I tried the standard gs version but it not appear that is was going to work well with the 36. I have heard that Calfee has had success getting the 11-40 XTR cassette to work well with the k-edge caged rear DI2 rear derailleurs. We may consider getting one for a fall trip to Croatia for the steep climbs there. It would be nice if someone would come up with something like Wolftooth components goat link for road derailleurs as it would be much cheaper solution to this issue. I did see a custom tandem(Cervelo one off with unique couplers) using the 11-36 with a 6870 GS caged derailleur but it had a longer derailleur hanger fitted. Bottom line the K-edge works well.

Bad1

Kind of interesting the 11-36 cassette 11 speed I know of only one mfr. IRD producting a 11 speed in this combination also a 11-34, so is this a 10 speed cassette. Our Macchiato Dura Ace di2 with a short cage has no problem handling a 11 speed 11-32 cassette with either a mid-compact 52-36 or a compact 50-34 chain ring & able to run a cross chain with no problem, without having to do funky B screw adjustments. I really would think the new di2 mid-cage ulterga would be able to handle a 36 tooth lower ring. As far as running a 52-34 combo I did quite a bit of experimenting last summer with this combination, i'm here to tell you it was funky shifting up or down, it was just plain clunky I could'nt live with it, so I threw the 50 tooth chain ring on with the 34 and it worked like it was designed.

akexpress 

Actually there are least two manufactures making 11 speed 11-36 cassettes. Sram and Santana. Santana did a run of these cassettes before Sram's came out and we are running them on our wheels. It shifts great as it was supposedly built on Shimano blue prints specs. I do not have any experience with the Sram cassette. I do not think even with a funky b screw a 36 cassette will work with a GS cage. The K-edge moves the upper jockey wheel down and back so it shifts very well.