rosefarts

More or less posting to confirm what I’m already thinking.

I was thinking about AXS but it seems like I’d have to change too much. Besides, the bike is factory predrilled for DI2.

I want to make the switch to 1x electric on my Swiss Cross. It’s currently running mechanical Rival 11. I have two XD cassettes, 10-42 in heavy steel and 10-44 in svelte lightweight (the stock 42 is replaced with a wolf tooth 44).

I’m happy enough with my gearing and don’t feel compelled to get 12 speeds.

My thought is GRX shifters and brakes, no dilemma there. I’m thinking that an XT di2 derailleur might provide me with a better range on the bike. Is there any disadvantage to that?

What am I missing?

unterhausen

Is this because you froze your hands? I really started thinking about electronic shifting after I couldn't shift on a very rainy ride.

rosefarts

It’s not the first time I’ve been frozen. Not a problem.

I wanted electric as an upgrade and I’ve never liked the double tap actuation anyway. I think rival is finicky and requires a ton of adjustment to keep working. I have discovered that those levers have a flaw for my hands, on bumpy descents in the drops, my hands slide down them. This doesn’t happen on curved levers. It’s too bad really, since I really like tumor on top of sram hoods when more upright.

Also thinking about price. If I go 12 speed AXS, I need a whole new group, including XDR driver. For di2 11, I only need shifters, brakes, and derailleur.

Badger6

Di2 is no brainer, for you. IN stead of trying to decipher what you have and what you'd need (I think because it's 10pm in Belgium, and I might have had a few beers with the club after today's 180km road ride to the sea coast)....

Here's what my '21 Diverge is rocking, in Di2 trim;
Levers: GRX ST-RX815-R/L
FD: na
RD: RD-RX817
BB: SRAM DUB (BSA)
Crank: Quarq DUB Carbon with DZero Spider, 46t chainring (42t swaps in on hilly courses)
Cassette: SRAM XG1175 (10-42)
Front brake: BR-M8120 (4-pot post mount, on a flat mount to post mount adapter...much better modulation, and tons of stopping power, maybe more than I need)
Rear brake: BR-RX810-R (flat mount, rear)

As you can see, really you just need the levers and correct RD. I chose to run the SRAM cassette on an XDR driver (with spacer to make the MTB cassette compatible) so preserve the top end while getting the low end I wanted for loose gravel climbs. The key thing is that the move to Di2 for you seems pretty straightforward, really just levers, brakes, and a RD. You don't have to run a SRAM cassette, I just chose it since my wheels had the XDR free hub included when I bought them, but if it hadn't I'd have stuck with Shimano and suffered some top end loss, though in reality, I'm not sure how much it would have been in practice.

Go for it. Di2 is bombproof. Once properly set up, you can ride it forever without messing with it beyond chain maintenance and changing cassettes, and of course charging it up!

Steve B.

I say don't do 1X but instead do a 2x 30/46 crank. Di2 is about the best shifting of any group and there's no reason not to take advantage of superior front shifting.

Koyote

Or the GRX 48-31 crankset with its matching front derailleur… A brilliant combination. If I ever buy a new road bike, I would probably just go with that. I really don’t need a 50 tooth chainring.

Metieval

If you go di2, definitely consider going 2x. Auto trim... it is a wonderful thing.

Steve B.

And I can see where Synchro would work very well on a gravel bike.

rosefarts

All decent thoughts. I will consider them.

Nobody has mentioned the rear derailleur. The GRX claims 42 teeth max, I’m planning to run just beyond that at 44. The XT di2 rear mech is a tad cheaper and can throw that easily. Is there any reason at all to consider GRX instead? Everything I have read says the two are compatible.

What are some totally *****in mineral oil brake options? I don’t have my heart set on Shimano. Currently at 160/140 but can go 160:160 if it makes sense.

Tell me more about Synchro. Right up, left down. The brain figures out the rest? Makes sense. So if I chose to do this 1x, I could theoretically add a front derailleur in the future if I cared to so? I mean I could keep the system but add a chainring and F derailleur and keep the same basic function. It’s an interesting idea.

softreset

There's three buttons on each GRX Di2 shifter. The two on the shifter paddle and then one on the upper (inside) of the hood. I personally have configured my synchro to be:

- Both left paddles is shift up
- Both right paddles is shift down

The inner button is the opposite.

- Inside left button is shift down
- Inside right button is shift up

It's rare that I use that inside button anyone and my thought process with having it opposite is that in the event I were to damage one of the shifters I wouldn't be limited to only up or down from whatever gear I was in to get back/home/etc. I've been extremely happy with the 48/31 - 11/34 configuration. I haven't done any loaded touring on the bike but for the rides I do if I'm out of gears at 31/34, I'm either in way over my head or I need to evaluate a hike-a-bike.

Badger6

@rosefarts, on Di2, a road (GRX) shifter will shift certain MTB RDs. Check the Di2 Compatibility chart to verify the model numbers.

Shimano hydro brake systems are ONLY mineral oil compatible. You aren’t locked into Shimano calipers, but you’re locked into mineral oil, as the shifters cannot be used with DOT5 fluid, the seals will deteriorate.

Yes, if you build it 1x, you can always add a FD later. The left shifter will be capable of running an FD, whether the system has one or not. Synchro shift achieves it’s magic by utilizing a specific shift point, going up or down the cassette, using the shift paddles as they’ve been programmed to shift the RD. When the designated shift point is indicated, the FD will move up or down accordingly, and the RD will adjust the gear position to allow for a “sequential” feeling shift.

rosefarts

It is too bad they don’t offer a blank left lever that matches the DI2 right. That seems to be a major advantage to the SRAM offerings.

faulker479

If you think about it, that removes the versatility the system offers. The buttons can be configured in many different ways. You can setup Di2 to shift like eTap. You can mirror the right side. You can also assign those buttons to work with a Garmin Edge. Or simply leave them unassigned. There is no side to side movement on the lever so you always know where to reach for braking.

msu2001la

You can use the XT Di2 rear derailleur with GRX Di2 shifters. If you ever want to set up as 2x, you have to match front and rear derailleurs, so you'd have to find an XT Di2 Front Derailleur (yes, they exist...). I guess that might be the only downside vs GRX.

I'm not sure about exceeding the 42t max cog with the GRX RD. Historically Shimano has been conservative on these numbers and it might handle a 44T with a road link. The XT RD is good for 46T in 1x setup, so probably a better choice if you're set on that gearing.

Badger6

The extra 2 teeth can be handled by the b-screw. With a bit of careful tuning on that screw, the RD will shift fine through the entire range.

Fentuz

a bite off subject but in order to avoid this on rainy day (common thing in the UK), I fitted some trimmed BMX brake lever sleeves (silicone).

dvdslw

I'm running Ultegra di2 shifters with an XT rear derailleur on my Warbird. It shifts beautifully and has plenty of gearing with a 10-42 XX1 cassette and 42T front 1x chainring. I personally like the size and shape of the Ultegra hoods compared to the GRX. These days its all about what you can actually find to purchase in the current market and like others have said everything is pretty much mix and match except derailleurs. You must match the derailleurs by discipline so if using mtb derailleurs XT & XTR only but GRX will mix with Ultegra and Dura Ace. Shifters don't matter at all so use whatever you can find.

rosefarts

I think the part I may have forgotten is about the stuff to make it work.

The lever and caliper combos I’ve seen seem to mention pre bled. I guess that means they come with hydraulic lines.

Upthread I mentioned that the frame is already drilled for Di2 internal routing. So that should help.

I need a battery and it can go inside the seat post. I like that idea. I’m sortof thinking that if it has to go on the outside, that’s a deal breaker for me. I like my aesthetics.

I need a charger, I guess it’s sold separately, not included in the package. I definitely want a system that I don’t have to take it apart to charge. So that’s another add on.

And I need a junction box, maybe two? I don’t know. The pics I’ve seen online have something strapped under the stem and something else on the frame.

It gets a little confusing but it seems like I can get one that fits inside the handlebar (probably would need a predrilled bar for that).

So I guess my concern here is being able to get the whole thing done internal. Without bunches of wire or boxes strapped to the outside.

That would probably be the biggest advantage of SRAM. Just screw stuff in and open the app.

It’s an expensive enough project and just enough beyond my expertise that I’m tempted to just walk into a shop and have them tell me what I need. But what’s the fun in that?

Steve B.

The basic and actual parts needed for Di2 are:

-2 - Shifters, L & R
-R derailer
-F derailer (unless1X)
-Battery, order a shim that tucks the battery up into the seatpost.
-A junction, older design mounts on a thick rubber band under the stem, new designs can install on end of a drop bar - BUT that means you need to get a drop bar pre-drilled for Di2 cables (1 ea. at the shifter location, one near the stem) OR you get to drill your bars. A junction is the connection point for the shifters and the E-Tube cable that enters the frame somewhere near the headtube and goes to to the B junction, it also has the Battery charging port and some indicator LED's as well as a button that access various functions (shift mode, battery status, etc...).
-B junction, typically installs in the downtube near the b-bracket or the bottom of the seat tube near the b-bracket, both require the crank and b-bracket be removed to access these locations to install the B junction, which takes the single E-Tube cable from the A junction and splits it 3 ways - battery, R derailer and F derailer
BlueTooth transceiver, if you want to use an iPad/phone to connect with the E-Tube software and/or a GPS computer (useful in me experience).
- Assorted wires, usually at least 6, sometimes a 7th short 15mm if you install a BT transceiver right under the battery (a good place on a non-metallic frame)

I re-used my 105 crank and rim brakes so did not need to purchase those, the system works fine with these mechanical components and in any event you would receive the same items in an Ultegra version if buying soup to nuts.

Badger6

First, study this website. It will list exactly what you need to build a Di2 shifting system. Also, take a look at the diagram on page 32 in this manual. Hopefully TerryDi2C will happen along, he has devoted a lot of time to deciphering everything Di2 related, including some off the books troubleshooting, and he owns/built the website linked and he also hosts many of the Shimano manuals.

As the poster above noted, ignoring wiring for a moment, there are basic hardware items needed to make a Di2 system. Some are mandatory, like the levers, battery, junctions, and at minimum the RD. One is not, the FD if you’re building a 1x system. To make things easy, there are no “dummy” shift levers, as noted above, this provides flexibility and later add on options that consist of buying a at minimum only wire and a FD if you’d like to convert to 2x.

A couple of thoughts to help answer your questions above, and provide more info:
1) a frame predrilled, molded, etc., for Di2 will get all the cables and battery inside the frame. Depending on your bars, you may have cabling exposed front he inside edge of the bar tape to the frame entry points (usually on the down tube).
2) If buy a kit*, the charger is usually included. *Kits are sometimes a full gruppo, or sometimes just shifters and derailleurs, and always include the junctions needed.
3) There are two types of A-junction, the original type that have either 3 or 5 ports and are mounted under the stem, or the newer round type that can be fitted in a bar end (assuming at least one drilled hole near the bar end), or in the frame or seatpost assuming a properly sized hole and mounting hardware. Remember, the A-Junction is where the charger plugs in also.

It’s not hard to figure out once you first determine the components you need, and map out the wiring. THe real hurdle will be sourcing everything right now, due to parts shortages/availability.

TerryDi2C

Thanks! Yeah... ask me anything :-).

It may be worth knowing that Shimano are about to announce their 12 speed semi-wireless DURA-ACE and Ultegra Di2 groupsets (august 31) and while you won't be able to get your hands on those for a while (shortages/availability), I do expect a lot of current generation components to appear on ebay / facebook marketplace.

Bryan C. 

This video is what I followed when installing my bar end junction port. It shows how to wire up the system and where to drill holes in your handlebars. Pretty informative.


Another video explains how to run a large cassette with a 2x 815 RD setup. This guy did some long term testing and came up with a great solution to the b-screw dilemma. Even though I feel it's a non-issue I did follow his advice when recently changing out my cassette (again).

https://bikepacking.com/gear/wide-range-grx-2x11/

And since I mentioned cassettes, one of the big reasons I changed from a 1x to a 2x system is the lack of a wide range 11 speed cassette that has manageable steps and gravel friendly gearing. The e-thirteen 9-46 has excellent range but wide gaps that didn'tplay well for me with larger chainrings. The 10-42 Sram isn't very well spaced in the middle ranges. The Shimano 11-42 is better spaced, but still not great in the lower gear ranges. I currently have an 11-40 Shimano cassette installed but haven't had much time to test it. From the limited rides I have had it seems like a great fit with the 48/31 810 GRX crankset.

I initially thought the Di2 was going to be cheaper than a mullet style AXS setup but one you buy all the needed cables and junction ports it was comparable in price.

rosefarts

I sort of jumped the shark on this one.

I like tinkering and making things work. I also being the odd man out.

So I ended up with an Archer D1x Trail system and the remote that specifically goes into the TRP Hylex RS brakes. It’s pretty much a cable pulling motor that connects to a wireless shifter. Totally customizable for any number of gears. It would shift an uneven cassette if you asked it to.

Not installed yet but I’m looking forward to putting some time in on it.