FatBottomedGirl

Hey guys,

I must admit I have been getting sick lately of my transmission, the fine tuning to set it up perfectly, especially the ring shifting is a pain...

Anyway, I googles a bit about the Di2 and looks like it's not even as expensive as I thought it to be...

Now I have three questions that should be simple enough for anyone who has handled these babies in the past:

1. The kit I am looking at comes with no EW-SD50 cables as they say. These are, per my understanding the standard electric cables that "connect stuff" in the Di2 paradigm. So how many of these do I need?
2. The B junction usually mounts under the bottom bracket instead of the cable guide. My frame has that weird internal/not-really-internal routing... and no removable cable guide under BB,... Is it possible to cable-tie de B-junction under the chain stay?

trailflow1

Hi, Can you be more specific of which kit you are looking to buy - Dura Ace 7970, Ultegra 6770, Ultegra 6870, Dura ace 9070 ? and is it internal or external wiring/battery ?

If you plan to go internal wiring/battery with (6770, 6870, 9070) then 6 EW-SD50 (e-tube) cables are needed. These need to be the correct length which will depend on your frame size. Its best to measure each section with a tape measure against your frame. Remember to account for any slack you may need.

2 shifter cables (350mm each)
1 down tube cable (around 1000mm or more)
1 battery cable (around 700mm) edit should be 400mm
1 front derailleur cable (around 500mm) edit should be 300mm
1 rear derailleur cable (around 550mm)
Junction A box
Junction B box

If your frame is internal routing compatible, the Junction B box can go inside the bottom bracket provided there is cut outs inside to hide it in the frame,and it is accessed through the bottom bracket (by removing the crank). If you plan to go external wiring you can certainly cable-tie the Junction B box under the chain stay. But it will be more exposed to water/dirt. There may be a better place to put it. Like near the front derailleur or battery. It all depends on how much slack cable you will have.


AFAIK Dura Ace 7970 uses a different system to E-tube wires and is not compatible,and is seperate from (6770, 6870, 9070)

FatBottomedGirl

Hi,

Sorry,... should have been more specific.
I am considering the Ultegra Di2 6870 w/ external routing. This one to be specific (hope I'm not breaking any forum rules by linking a commercial website directly...).

I need external routing because while my frame is made for internal routing, it only accepts mechanical cables as the spot the cables go in the diagonal tube are just large enough to fit a cable, possibly a thin liner but not an electric cable with its connector.

Thanks for the details about the cables. I will consider measuring precisely but is it that much rocket science? I mean, if I have ~5cm extra on one of the cables is it really bad to loop it somewhere to reduce artificially? (I mean, is it bad beyond the fact that it might be inelegant...)

Also, just a little wondering about your measures. I do understand these are educated guesswork based on experience, that are not 100% accurate since every frame is different, but the big picture must be right.
Therefore most of these figures make sense but I wonder:
- 700 mm for the battery? that is longer than the top tube! probably you have in ming the set-up with the battery inside the seat post but still, the cable only goes from the battery to the B-junction, right? how can it be *that* long?
- 500 mm for front mech? it just goes from the B-junction to right-above crankset, why does it need to be half-meter?

And thanks for the clarification over the junction positionning. Is it safe to say (I admit I exagerrate a little) that it can be put anywhere on the bike (though the BB/crank/stay/seat tube areas are preferred for obvious reasons) as long as I can safely plug all the wires and secure them to prevent any slack wandering in spokes or cranks while at 30 mph )

Anyway, thank you, now that it looks that nothing technically prevents me from having Di2, it makes me want it even more....

trailflow1

First, most importantly. Your wheels need to be compatible. Are you currently using 11 speed wheels and 11 speed cassette ? i assume you are.

No its not that bad having extra cable, Its far better than being too short. It will be fine.

You are correct on the numbers. They were wrong. The front derailleur should be 300/350mm, and the internal battery cable 400/450mm.

As you are going External its best to ignore my cable length estimate for the battery. I am not sure exactly what the
external length should be. I dont have any experience of that set up. Im guessing it would be 300/350mm.

Pretty much. Yes. Another thing to include. Depending on which option you choose from the drop down menu on the link. You may not have to buy '2' 350mm e-tube shifter cables.

If you choose the 'EW67A-E' from the menu. This is a junction box 'A' and shift cables in one. Already attached.






If you choose 'EW90-A' from the menu. You will need to buy '2' 350mm e-tube shifter cables

or if you choose 'EW90-B' from the menu. This junction box comes with 2 extra ports for adding satalite shifters to time trial bars. You will need to buy '2' 350mm e-tube shifter cables.

(Junction box A or B also have charge port's for internal batterys. They still work fine with External set ups)

Another possible option you have (though i cannot confirm it will work) since you say you can't attach the bottom bracket 'Junction SM-JC40' to your bike. Is to replace it with the much smaller 'Junction SM-JC41'.

FatBottomedGirl

Good point. I had considered this and yes the wheels are compatible, they do support 10 and 11 speeds. But I will need new cassette and chain.

Fine. Actually, I will probably proceed this way: order the kit, mount everything I can mount and once I have all of this mounted, I will be able to measure even more accurately the wire lengths I need and get these.


That was another concern of mine. When I read the Shimano documentation, I see no mention of EW67A-Em only EW90-A and -B. so I was wondering whether that EW90-A item is not from some older version or whatnot and if it is fully compatible...
But picking this one would save me about 60 EUR ... and that cannot be bad

trailflow1

The EW67A-E was introduced with the old Ultegra 6770 10 speed Di2. There are reports it is fully compatible with 6870.

It is confirmed working on this link. if you click Q&A then 'Is this cabling set compatible with Ultegra 6870 Di2?'
Wiggle | Shimano Ultegra Di2 6770 Handlebar Cable Set | Gear Cables

The EW90-A and B are the newest ,designed to work with Ultega 6870 an Dura Ace 9070.
[h=1][/h]

FatBottomedGirl

Thanks. So I understand the "smartness" of the 11-speed shifting, as it was the case in mechanical is handled by the shifter only (possible the derailleur?) but the junction is really just a way to group wires... Right?

trailflow1

yup, correct.

AFAIK the 'brain' of the system is the junction 'A' box which can also tell you your battery level , and let you fine tune the rear derailleur position (if you hold down the small button,then click the shift levers to adjust.)

The shifters are the control point. They send the signal (the shift) to the motors on the deraillers,which do all the work.

FatBottomedGirl

Are you sure? because in this case, the EW67A-E acts as an "A" junction box with its battery level button and everything, which is why the fact that this item designed for 10-speed Ultergra 6770 works with the 11-speed Ultegra 6870 was far from obvious.

Even though here it seems to be the case which is comforting ...

trailflow1

Yes. the EW67A-E is a junction A box.

Its the rear derailleur which knows and determines which speed the system is. Up until recently you could upgrade a 10 speed 6770 system to 11 speed, If you bought a rear 6870 11 speed derailleur. I think Shimano have now clamped down on this by releasing a firmware update which prevents it from working.

bored117 

Bit of thread resurrection but I would just like to mention that EW67A-E doesn't work with internal battery even with latest firmware. I happened to have 3 DI2 units in my bikes and on mix and matching found this out... (6870, 6770s)