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If I purchase a bike with shimano di2 will it be able to readjust its rear dérailleur to accommodate different rear hub types? If this is possible is it a quick and easy process that can be done before a ride or does it require the shifters to be plugged into a computer?

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    To an extent, any answer here would be a case of "watch this space", as the software/firmware is becoming more and more functional with time. I just mention this because it means that any answer given now might not be valid next year, for example. – PeteH Mar 13 '15 at 13:02
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Quick answer:

You would need to use a PC, and you would need to make sure that the wheels had reasonably close original chain line positions for this to be possible. If not, then no, you can't do this.

Long answer:

Shimano's E-Tube software does allow you to save presets for adjustment and switch settings. That means you could have multiple presets saved for the electronic portion of the shifting adjustment.

However, if the difference in required settings between the wheels is more than could be adjusted for by adjusting cable tension on a mechanical system, then you will still need to adjust the limit screws on the rear derailleur.

Since those are still a manual adjustment, there is no way to ensure that swapping between wheels on an electronic system is possible using only the preset system.

Also, there is no way at present to swap between presets on the fly with the road Di2 system, so you would need to plug the system into the E-Tube software on your PC.

There is the the possibility that this might change, since the new 2015 XTR Di2 system has the ability switch between shift maps using the SC-M9050 Display Unit. At present, though, shift maps only affect the order of shifting for XTR's Synchro shift system. They do not allow shifting between preset shifting adjustments.

Since the Display Unit is functional with the road Di2 systems, it is possible that a firmware update could enable the ability to swap between presets. Without the ability to make the manual adjustments the preset swapping would have limited utility for this purpose.

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    If anybody from Shimano is reading this, it would be nice if you could interface with the shifters from your phone. Even if it required a cable and a phone with USB OTG port, I'm sure it would be appreciated. Not that I think I will ever own di2, but I'm sure the people who bought it would like a feature like this. – Kibbee Mar 13 '15 at 15:06
  • @Kibbee the latest Dura Ace group talks wirelessly between the shifter and the derailleur (Bluetooth presumably). So there's no reason why a wireless connection with the pc (or with a phone) could not also be possible. If anyone has any documentation on this group, btw, I'd love to see a link - I got very limited info from someone on a team. – PeteH Mar 13 '15 at 19:35
  • @PeteH Dura Ace 9070, the latest Shimano Di2, doesn't and can't communicate wirelessly between shifter and derailleur. There is an accessory called D-Fly which allows limited wireless data transmission to a connected cycling computer which has been designed to accept it. It also allows buttons on the shifter to control the screen on the cyclometer. – zenbike Mar 14 '15 at 16:38
  • The communication protocol it uses is ANT+, not bluetooth. Since there is a wire connecting the derailleur and shifter, there is no need for wireless communication there. – zenbike Mar 14 '15 at 16:39
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    Not for Shimano, no. With SRAM's upcoming electronic group, there is a wireless system in the prototype phases, but it's not close to release. Shimano doesn't see the utility, since on a wireless system, each component has it's own battery, and needs to be charged separately. In addition, if your friend said the only wire was going to the battery, that would indicate a single battery system, and that isn't possible with a wireless system. Each radio receiver needs a power source. If there is no wire, it needs its own battery. – zenbike Mar 14 '15 at 17:36

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