Start 2019 by Building your Gravel/CX Rig with Di2
"Whoa, dude. Di2. And is that 2x?" Yes. It is electronic shifting on a cross bike. And yes. There are two chainrings. One-x mechanical is the old way; the new way is here, and let me tell you: The whole thing is excellent.
I think for the purposes of a review, it's worthwhile to know what I've used in the past. My first "Real Road Bike" was mechanical Campy Record 11. You know, real. As I got into cross, I moved all my bikes (even road) to SRAM 1x, because that's what you're supposed use in cross, and having backup pieces to pull from a road bike is helpful when things break. This last road season, I tried Di2 for the first time and was stunned. The setup is so easy – once you plug everything in, it just works. And as long as you've got a charge, it consistently functions up to a very high standard for silent, perfect shifting. The first shift you make with Di2 is the same as the 10,000th. The real difference-maker, though (at least in a road context) is the quality of the front derailleur relative to its mechanical peers – it's in a different league. I decided halfway through the season that Di2 is the right way to shift a racing bike* and committed to it.
The Primary Objection
The main thing I hear from folks about Di2 in the cross context is, "sure, that sounds nice, but it's crazy expensive. I race what I can replace."
I get that. Cross stuff doesn't need to be fancy to work well, you definitely don't need Di2 to win a race. You don't even need SRAM Force – a mix of Apex and Rival is just fine for 100% of people's needs. Pros aren’t gaining or losing places because they have Force or Rival or whatever, and especially in a 1x context, all the clutched RDs work about the same.
That said, putting together and maintaining an Ultegra Di2 bike isn’t that much more expensive than going with SRAM Force 1.
Initial setup costs (no rotors for each)
SRAM Force 1 Hydro – $1,050
Shimano Ultegra 8070 – $1,500
Okay. So that's 50% more expensive, but it’s electronic (apples to oranges), and built to a higher level of finish than SRAM. Save your money, don’t get a powermeter, and you’re good.
BUT WHAT IF I BREAK IT!?!?
SRAM Force 1 HRD Levers – $285 ea
Shimano Ultegra 8070 Levers – $290 ea
Shimano is 2% more expensive. Cool. That's the same in my book.
SRAM Force 1 Rear Derailleur – $214
Shimano Ultegra 8050 Rear Derailleur – $230
Shimano is 7% more expensive. That's more, but it's only 2 beers more. Fine.
So let's say you kill a derailleur in the mud. Or in a crash (which is less likely with Shimano derailleurs, because their design keeps them tucked out of the way). Or you over-tightened your levers and rip one apart. Your fix-it costs the same as SRAM, especially when you figure that you never need to replace your derailleur cables ever again.
There are two cross-relevant things about Di2 that are worth noting.
First: it always works. In the mud. In the muck. In the wet, whatever. The motor powers through whatever is there, and the chain always always always goes in the right spot. Foul-weather performance benefits from Di2 are a non-obvious thing for most; it seems like an electronic system would be less good as conditions get worse. Nope. The thing is sealed and is awesome no matter what, and you don’t have to replace the cables.
Second: if you want, you can have a front derailleur, because electronic front derailleurs work perfectly all the time. Have you noticed that mechanical front derailleurs are constantly being redesigned by Shimano, SRAM and Campy? That’s because shifting the between the front rings is an engineering challenge that hasn't yet been solved perfectly. Don't ask me why. But once you put a little servo motor in there, everything is fine. The front shifts under load, no matter what, every time. So it's an option if you want it – and I've appreciated having that option this year. You can be motoring along in the 46, dump it to the 36 to ride the run-up, and then put it back in the 46 when you get over the top. Jumping ten teeth in less than a second is actually pretty helpful.
What about dropped chains? It hasn’t happened to me, yet. I assume that it will, but so far I haven’t even gotten close.
If you’re not into front derailleurs, that’s fine too – 1x drop-stop rings from AbsoluteBlack or Wolf Tooth Components are simple to install on Shimano cranksets, and all but eliminate dropped chains. But if you’re into more security, Shimano makes a clutched Ultegra derailleur under the “RX” badge. The clutch is easy to disengage and works flawlessly. I’ve been running one for the last four races, and it is almost entirely invisible, performance-wise – you don’t notice not having chain slap, because the bike just gets more consistently quiet.
Anyway. Di2 is the one true god.
*Obviously: cabled derailleurs are essential for situations where you're away from a power source, or can't rely on fancy bike shops having the special parts you need.