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Can a 6770 Di2 rear derailleur be replaced with the Dura Ace 7970/9070 and function properly?

Is there any advantage to doing so?

I banged up my rear derailleur and want to replace it and just wondering if there are options other than the 6770.

Thanks
 

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So if I'm understanding you correctly. A ultegra 6770 di2 system can be converted to a 11sp system by merely changing to 9070 RD and reprogramming junction box? Asumming of course with a 11 sp cassette and compatible hub.

If so 6770 shifters and FD will work still.

I thought the 11 sp chain is narrower than 10. That's why kmc sells specific 11 and 10 sp missing links.
 

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I have asked this question of Shimano techs & although they will not confirm or deny anything officially, I am led to believe you can upgrade 6770 to 11 speed with only a cassette/chain & compatible wheel. Have not tried it & cannot confirm, but techs would not say "NO" when asked directly. KMC 11 speed links are based on Campy 11 chain width(narrower). As I understand it(cannot remember 100%), Shimano 11 chain is same outer width but narrower inner width(thinner cogs). Someone feel free to correct me if I'm wrong.
 

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I have an unofficial answer from our contact at Shimano and it's an interesting one. If you have upgraded the firmware of your 6770 setup to the newest version, then putting a 9070 rear derailleur will effectively make your system function as 11sp. Put on an 11sp cassette and chain and you're golden. The front derailleur will function, but at a 'B' compatibility level due to the wider cage dimension.
So yes it will work, BUT it will no longer function as an 10sp system and will not shift on a 10sp cassette.
 

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That's more reassuring info. I'm sure no one at shimano wants this as widely known since it may cannibalize the newer 9070.

I would be willing to try it but my existing hub is 10 sp.

Are the 7900 cranks 11 sp chain compatible? I'm particularly curious about chainring teeth thickness.

If the 9070 RD is a can bus network the 9070FD may work as well.
 

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I can't imagine they think it's a very big secret. He was very upfront about the compatibility and the see it as a selling point. The 'push' to do a full upgrade is weight based, 6770 is still a heavy SOB.

The crank will work fine. The inner dimension of the chain is unchanged, meaning tooth thickness on the crank is the same. In fact the cassette cogs are supposed to be the same thickness as well with the spacing being the only change. I haven't measured mine so I can't say for sure, but again, from my reps mouth.
I'm currently running 9000 (mechanical) with a Rotor 3D+ crank & Praxis rings. It works as well with 11sp as it did with 10sp.

As for flashing the derailleur itself, the software knows what specific derailleur it's connected to, I don't think the it will allow for flashing a ROM to a device it wasn't 'designed' for. My understanding is that it would have to be a hack/mod.


That's more reassuring info. I'm sure no one at shimano wants this as widely known since it may cannibalize the newer 9070.

I would be willing to try it but my existing hub is 10 sp.

Are the 7900 cranks 11 sp chain compatible? I'm particularly curious about chainring teeth thickness.

If the 9070 RD is a can bus network the 9070FD may work as well.
 

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10spd and 11spd will be determined by the shifters, not the deraillieurs. So if you have 6770 and you add the 9070 rear brifters, you system should automatically become 11spd.

And the same can be said if you want to use your 10spd wheels on 9070. You must have 6770 brifters for it to work.
 

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10spd and 11spd will be determined by the shifters, not the deraillieurs. So if you have 6770 and you add the 9070 rear brifters, you system should automatically become 11spd.

And the same can be said if you want to use your 10spd wheels on 9070. You must have 6770 brifters for it to work.
Incorrect. My Shimano rep says change the RD and Cassette and you're good to go.
 

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Why the rd? It was suggested to me by Shimano techs that 6070 will do 11. They said travel was the issue, but 10speed der has plenty of extra movement to cover extra cog. Shifters and derailleurs are "dumb" and have no mechanical limit at 10. I'm led to believe that cassette(wheel), chain & reprogram are all that's needed! Maybe a 9070 main junction box as its the one "smart" piece...? But current e-tube hardware makes no distinction, so I think not.
 

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Why the rd? It was suggested to me by Shimano techs that 6070 will do 11. They said travel was the issue, but 10speed der has plenty of extra movement to cover extra cog. Shifters and derailleurs are "dumb" and have no mechanical limit at 10. I'm led to believe that cassette(wheel), chain & reprogram are all that's needed! Maybe a 9070 main junction box as its the one "smart" piece...? But current e-tube hardware makes no distinction, so I think not.
It was irresponsible for your tech to say that, when it is not possible. The throw of the 6070 is not enough and there is no program to support it regardless (and I'm not one for hacking it to have little support and sketchy functionality, all for one more cog).

However, adding a proper 11 rear, cassette, chain... and for some a cassette body swap (King hubs rule). You can be on the new DuraAce 11 where it matters most and I think that in itself is pretty cool, for those who want it.

I've been perfectly satisfied with the multishift update that I don't feel compelled to go through the hassle of an 11 update just yet (and my other bike has SR11 mechanical so I know what I'd be missing, in terms of a extra gear anyway).

When they make the DuraAce stuff in something other then flashy silver I'll tinker but by then I'm betting some new Ui2 Ultegra 11 shadow product will be around, (I just got my Di2 so it's still fresh to me).

Now, I just need to get a Windows back end on my iPad mini so I can run the etube software through it, (or an iPhone).

Puzzles me why Shimano of all companies doesn't have an iOs app for etube. Now there's a hack I'm interested in!
 
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