How do you choose?
If you’re constrained by budget, do you factor in the course profile? e.g.:
twisting course where you are accelerating out of the saddle would push me to brake/shifter combo
But a flatter/less twisting course would make me choose the bar-end tt shifters.
Are the combo shifters really worth it?
Without hesitation you go both, for me this is why di2 shifting is the way to go for TT/Tri because you can shift from both positions. Why spend the money on having di2 and then save money by only having shifting on one position??? Totally a false economy.
If money was no option then I would totally agree with you.
Unfortunately I’m already compelled to spend 200-300 upgrading my old school Di2 to the current edition so I can attach more wires to eachother apparently. See here
I’ve just started assembling a Di2 groupset for my TT bike, and i have a similar dilemma to yourself.
My problem being that i’m on USE Tula bars, so they have their own brake pods which rules out the ST6871 shifter / brake lever options, but fancy having something other than the 671 bar end shifters, so i’m thinking about using the climber buttons (1 on each side) along with a 5 port A junction, to enable rear shifting from the base bar.
Or have i missed something blindingly obvious on the compatibilty front?
No, that seems doable; I would be just going for the 3-port junction box I believe.
I think you’re forced into that set-up if you’re restricted on the brake front and still really want to shift from the base bar.
If you cannot afford to make the upgrade now, save your money, and do it when you can afford it.
If you’re not going to put shifters on BOTH the bar extensions, and ALSO at the brake levers, you might as well just stick with mechanical shifting.
IME: The best/most-important advantage of Di2 over mechanical group—on tt/tri bikes—is the ability to shift from both positions/locations.
IME: The best/most-important advantage of Di2 over mechanical group—on tt/tri bikes—is the ability to shift from both positions/locations.
totally agree! Problem is I already have 6070(?) Di2 from 2013-2014 and I’m trying to switch out my handlebars to an aerobar combo with Di2. So either I go with one option or both. See link to my other thread in the original post above.
Thanks
IME: The best/most-important advantage of Di2 over mechanical group—on tt/tri bikes—is the ability to shift from both positions/locations.
+1
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will you need to upgrade to a wireless unit as well as the 5-port A-junction?
I was looking at the Dura Ace SW-R9160 shifters but may need to upgrade my whole system if I get these!
will you need to upgrade to a wireless unit as well as the 5-port A-junction?
I was looking at the Dura Ace SW-R9160 shifters but may need to upgrade my whole system if I get these!
From how i understand it (and i could be wrong!!) is that if you wanted to run the R9160 shifters as stand alone units, then you would need the DN110 battery, and the new wireless D-Fly unit WU111 to enable syncroshifting (1 button up. 1 down) so it shifts the front mech automatically dependant on where you are on the cassette. This would only need a 3 port junction box.
You could use them in conjunction with the ST6871 shifters, and a 5 port A junction, but program through E tubes so it only controls the rear mech; again 1 up 1 down but no syncroshifting. I dont know how many times you need to make front shifts during a race, but i cannot remember the last time i did…
For this method, you can use the old BTR-2 internal battery or the newer DN110, and BCR-2 charger, and use an old fashioned hardwired pc connection.
I’ve now got most of my parts (just waiting on some etube cables and free time), and then its time to find if my understanding is correct 
Nice one, thanks! It’s a bloody gong show really, despite Shimano’s excellent effort to update their techdoc website.
I think I’m going to try this guy to connect my future shifters to the existing system. I’m just not sure if I need to update the battery firmware? (it’s the old external BR1)
Yup. If and when I upgrade to Di2, it’ll be on both locations for me.
IME: The best/most-important advantage of Di2 over mechanical group—on tt/tri bikes—is the ability to shift from both positions/locations.
+1
will you need to upgrade to a wireless unit as well as the 5-port A-junction?
I was looking at the Dura Ace SW-R9160 shifters but may need to upgrade my whole system if I get these!
From how i understand it (and i could be wrong!!) is that if you wanted to run the R9160 shifters as stand alone units, then you would need the DN110 battery, and the new wireless D-Fly unit WU111 to enable syncroshifting (1 button up. 1 down) so it shifts the front mech automatically dependant on where you are on the cassette. This would only need a 3 port junction box.
You could use them in conjunction with the ST6871 shifters, and a 5 port A junction, but program through E tubes so it only controls the rear mech; again 1 up 1 down but no syncroshifting. I dont know how many times you need to make front shifts during a race, but i cannot remember the last time i did…
For this method, you can use the old BTR-2 internal battery or the newer DN110, and BCR-2 charger, and use an old fashioned hardwired pc connection.
I’ve now got most of my parts (just waiting on some etube cables and free time), and then its time to find if my understanding is correct
The D-Fly unit isn’t required for synchro shifting. It is an add on that allows wireless communication with the Di2 system. You can change synchro shift modes right from the Junction A unit.
I made the change last week from 10sp Ultegra Di2 to the DuraAce 9150. From the start I knew I had to change the battery to the DN110 and a new EW90 junction box for the E-tubes app to work, from there I ordered the R9160 shifter pod, cassette, the front and rear mechs.
The kicker for me is that I ride a P5 with Magura hydraulics so I knew I had to configure the synchro shift in order for me to shift the mechs with the R9160s. Everything works great but you have to remember that using the R9160 will reduce your reach as they are considerably shorter in length if you were using the previous version of the shifters and grip the top of them then I brought my arms/elbows back an inch on the pads.
Ah okay, thats how i read it though, and from looking at the tinterweb, a lot of other people read it that way too.
Perhaps its how shimano’s instructions sometimes don’t make sense…
Happy to be corrected 
@leahnp could you please draw out your set-up?
I bought new Ultegra 6770 di2 tt shifters to use with regular mechanical brakes (i.e. no shifters) and thought I could use the 4-way Junction B box to tie them into my old EM-41 Junction A box.
But nothing from my gears once connected up?! What have I missed?! Do I need the regular bar-end brake/shifter to route the TT shifter through? Or upgrade the firmware on the system?
What is an EM-41 “old Junction A”? Are you referring to the “3 way” SM-EW67 ?
Sorry it’s an “EW-67” yes
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Point #1: If you’re not going to put shifters on the aerobars, you might as well ride an aero road bike with mechanical shifters and clip ons.
Point #B: Given that we’ve established that shifters on the aerobars are essential for a TT/Tri bike, the question is whether you’re going to go forward with some sort of the supplemental shifter buttons (either the Dual Control brake lever/shifter assemblies, or perhaps a pair of “climbing shifter” buttons) on the bullhorns. I see this as the overriding advantage of Di2 over mechanical shifting. If you’re not going to exploit that capability, you might as well stick with mechanical shifting.
Hey Gary sorry I thought I stated somewhere that I bought tt shifters for the aerobars.
This is what it looks like right now: