Reviewed: Shimano XTR Di2 is capable, at a steep price

As a general rule, superlatives are to be avoided. Nothing is the best for every rider, everywhere.

During a week at Interbike, exhibitors, athletes, and other journalists asked me, “what have you seen that’s awesome here?” My answer was always the same: “I got to ride XTR Di2 at Outdoor Demo. It was amazing. Game changer. The best group.”

Oops, superlative.

But it’s deserved. For the few other industry folks who had spent time on XTR Di2, my remarks came as no surprise, as they had already ridden the completely new drivetrain and understood my amazement.

A drivetrain with a brain

Synchro shifting, which shifts the front and rear derailleurs with input into just the rear shifter, did not sound appealing. The Synchro system, when I first heard of it, seemed to remove a certain amount of control from the rider. I pictured myself sprinting over a rise in my big ring, and the system kicking me down into the little ring just as I crested the summit, leaving me in the completely wrong gear for the start of a descent. In reality, the rider still has loads of control, and the system adds to the rider’s experience. It doesn’t take away from it.

My first ride on XTR Di2 was aboard a Pivot Mach 4, which has been designed to accommodate the electronic system. The model I rode was the Bentley of mountain bikes, outfitted with a Fox 32 fork and Float shock, both equipped with the Shimano Di2-powered Fox iCD electronic suspension controls. It was a 2×11 drivetrain with a 36-26 chainring combination. The wheels were Shimano’s new carbon XTR Trail wheels, wrapped in fat Geax tires. If only there were a Di2-powered dropper post, everything I could have needed would have been a quick click away from the grips.

XTR Di2 setup

The Synchro system has three shift settings, S1, S2, and Manual. The shift settings are displayed and changed on the SC-9050 Display Unit, which also acts as a junction box for the shifters and the Fox iCD system. The Display Unit shows whether you’re in climb, trail, or descend mode on the shock with large arrows on the right side of the screen. The Display Unit, like the junction box on Dura-Ace Di2, is the command center of the XTR Di2 system.

On my test bike, the S1 shift setting was set up for more aggressive riding. It would not shift the front derailleur until I tried to shift past the largest cog in the rear. When I did make that shift, the front derailleur would shift, but so would the rear, moving my chain down to the second largest cog in the rear, making the shift up front a smaller jump in gear. It would shift back into the large cog if I dropped past the fourth largest cog, and, like the shift into the small ring, the rear derailleur would push the chain up the cassette when shifting into the big ring.

It was doing, then, exactly what I normally do manually, but faster, more precise, and with less brainpower required.

Before the system makes a chainring shift, the Display Unit lets out a noticeable beep to notify you that another shift of the rear derailleur in the direction it just moved will shift the front and rear derailleur simultaneously. The beep is loud enough to be noticeable, even when descending, but is not obnoxious. (I was pretty sure it was going to be obnoxious. I was wrong.)

The S2 Synchro setting is for more casual riding, and would shift the front derailleur down to the small chainring when the chain shifted past the third largest cog, rather than the largest as in the S1 setting.

Swapping between the various shift modes is relatively easy, performed by simply double clicking a button on the bottom of the Display Unit, directly underneath the display showing the current shift mode. It wasn’t so easy to switch that we’d want change between Synchro settings while riding, but it might be something a rider does at the start of a descent. You also need to cycle past the Manual mode, so to change from S2 to S1, four button pushes total. Shimano should make switching between shift settings quicker, if not easier.

All of this is customizable. For example, in the S1 setting, a rider can opt for the front derailleur to shift down to the small ring when shifting up from the second largest cog, rather than the largest, as it was set for my test ride. The rider can also program the system to shift the rear derailleur down two gears, rather than just one, when the front derailleur shifts. This would make the effective gear jump from big to small chainring less than a single rear gear change. This is a change we made after the first five-mile loop of the test ride.

The left shifter isn’t a necessity. Though I’m not quite ready to ditch the left controls just yet, it is an option for riders who think they can get by with a single shift lever and a dialed-in Synchro system.

XTR Di2 on the trail

I started my pedal at the Outdoor Demo in the S1 Synchro setting, the more aggressive of the two settings. Initial reactions had me as impressed with the Fox iCD controls as I was with the shifting performance. The iCD control was in between my right grip and the Shimano brake/shift body — it can be run on either the left or right.

The remote has three positions. All the way down is locked out, middle setting for “trail,” and all the way up for “descend.” It’s as quick as a light switch and the motor locking out the shocks moves similar to a Di2 front derailleur.

Once I got pedaling up the climb I started playing with the shifting. Naturally, I’m adapted to pulling the down shift trigger with my pointer finger, but with Di2 that’s not an option. With the electronic buttons so close — they are adjustable, but were slid as far apart as possible — and with gloves on, I was having a little trouble remembering what my fingers were supposed to do in order to make the shifts I wanted. It sounds silly, but the half-second it takes to remember what buttons to press to shift can be frustrating and on a technical trail, that half-second can get you bogged down.

I started playing with shifting the rear derailleur up the cassette to try out the front shifting. A little ways up the trail, the chain dropped when shifting down to the smaller chainring and I had to stop and get the chain back on by hand. I tried to replicate the incident by upping my cadence and shifting quickly, but I couldn’t get the chain to drop again. After the first loop we did, Shimano adjusted the limit screw so that the front derailleur would not have that problem again. The chain drop, therefore, was a small adjustment error rather than a symptom of a larger issue.

In the S1 Synchro mode, the front derailleur would have never shifted out of the big ring. The climb wasn’t steep enough for me to shift past the big cog while in the large chainring. On my second loop, I set the system to S2 for the climb. The less aggressive setting was a bit more relaxed for a slower pace. However, when I got to the summit, I switched the Synchro setting back to S1, as I knew I wouldn’t need the chainring to shift down, and I wanted to have full use of my cassette should I dump gears going into a slower corner.

On that note, dumping gears works better than expected. The larger bottom shift paddle has two clicks, rather than a single click, like in Dura-Ace Di2, so riders can dump two gears at a time. With multi-shift function turned on, gears will continue to dump if you hold the paddle. So, while I expected the system to not be able to dump gears quickly, it wasn’t a problem at all. At least not on the trails we rode.

The shifter design was my big hang-up.

After our first 5-mile loop, I wanted to play with my shifter layout as my fingers did not agree with the standard XTR Di2 configuration. This is where all of the Di2 systems shine — in their customization capabilities. We plugged the bike into a PC — Shimano’s E-Tube software is still not compatible with Mac — and reconfigured the functions of the shifters so that the larger bottom paddle on the left shifted my rear derailleur up the cassette, and the large shift paddle on the right shifted my rear derailleur down the cog. The front derailleur was controlled in a similar fashion with the small buttons on each side of the bar.

With this setup, my thumbs had a much larger target to hit when making the shifts that count, the rear derailleur, and I don’t think I even touched the front derailleur buttons. My right thumb, which has had a series of injuries and now sports some internal custom hardware, would occasionally bump the small shift button when I was trying to shift down the cassette on descents, but since the bike was already in the big ring, it didn’t matter. For riders who have spent any time on a road bike with Di2 sprint shifters, the switch I made is quite similar. It’s my favorite part of the system.

Bottom line

The difference in weight between an XTR Di2 bike and an XTR M9000 bike is the weight of the Display Unit, or about 30 grams. When the individual components are all weighed out, M9000 looks to be even lighter, but the weight saved by using electronic wires instead of cables and housing closes that.

Pricing is another story, and as you might guess, XTR Di2 is in its own stratosphere. A single-ring XTR Di2 system with cables, battery, and everything else you need will retail for about $3,500. Of course, a double or triple chaining system will add hundreds to that price tag thanks to the extra shifter, front derailleur, and chainring(s). The electronic system holds a $1,500 premium over mechanical XTR M9000.

My only complaints are that Shimano doesn’t offer slimmed-down, single-shift levers for the left and right sides for riders who opt for the single-ring system, but still want to use both hands to shift up and down the cassette, as I had set up the test bike for my second loop. Also, I still don’t understand why the Shimano E-Tube software does not work with Mac, or, better yet, via some wireless protocol. I can update the firmware on some power meters with my phone, so why do I need to find a window-enabled PC (akin to finding a Colorado Unicorn in media circles) to do anything to Di2?

This whole drivetrain, and even the XTR M9000 system, comes down to a need-want scenario. Do you need the electronic shifting Julian Absalon rode to a cross-country world championship earlier this month? No. Do you want it? Well, yeah, but we’d recommend buying your significant other something nice at the same time, just in case he or she disagrees with what you really need.

We pray that an XT Di2 option brings electronic shifting to people with more modest budgets. Until then, pony up, or get used to hearing your single and child-free riding buddy rave about his XTR Di2 drivetrain. It’s quite something.