Shimano Ultegra R8100 Di2 Groupset Review

Shimano’s latest Ultegra Di2 groupset has been slowly appearing since its October 2021 availability. Two years later, I’m finally gettin first-hand experience with what has historically been Shimano’s bread-and-butter offering. With almost all the goodness of Dura-Ace, but at a significantly lower price, Ultegra R8100 Di2 is also semi-wireless and 100% changed from the prior generation — including going 12-speed. But, does it maintain its legendary status of the best overall road drivetrain? I found out by taking the rough road to get there.

Shimano Ultegra R8100 12-speed Di2 Features:

• Semi-wireless design: wireless shifters, wired derailleurs and battery
• 12-speed with up to 11-34t cassette
• Hollowtech II cranks are available with integrated power meter
• Available with hydraulic disc or rim brakes
• Shifters use CR1632 coin-cell batteries with 1-2 yr lifespan
• Utilizes much of the same internals as Dura-Ace
• Battery life: ~1000km
• Weight: 2,716 grams (stated)
• MSRP: $2660

Ultegra Di2: The journeyman electronic groupset

After spending time on the Shimano Dura-Ace R9200 earlier this year, I was anxious to get onto the latest Ultegra R8100 as a more approachable 12-speed kit. The Japanese brand is rarely first-to-market, but instead prefers to take their time and perfect every minute detail before releasing any new product. After the past few years of supply chain issues, Shimano is back on track and outfitting stock bikes and custom bikes alike with their venerable Ultegra Di2 drivetrain.

My test period has been somewhat shorter than typical, but I’ve been uniquely pushing the limits of the Ultegra R8100 groupset aboard the Thömus Sliker X gravel bike. A gravel bike with a road groupset? Well… I asked the same question when the bike arrived, but looked at it as an opportunity to see just how capable Ultegra can really be. After many miles on gravel, singletrack and pavement, I’ll submit that the latest Ultegra Di2 is best-suited for road use. But, the definition of “road” is widening these days and Ultegra can certainly be confidently ridden on all flavors of roads and certainly smooth and fast gravel. Chunky, rough singletrack or gravel is best-suited to Shimano’s GRX lineup — with a pending 12-speed GRX Di2 kit coming soon.

As with all Shimano Di2 systems, there is a large battery that typically gets stashed in the seatpost or in the downtube. That battery powers the front and rear derailleur while the shifters run on individual coin cell batteries, which should be changed once per season. The new charging interface is a simple cable that attaches magnetically to the back of the rear derailleur. Gone are the days of a charging port stashed somewhere on the bike and a separate BluetoothLE / ANT+ unit because connectivity is built in. It’s easy to update firmware using the Shimano E-Tube mobile app (I updated the rear derailleur by syncing and leaving my phone next to the bike for a few minutes). I’m grateful that process has been improved because in the past, it was a crapshoot unless you owned a Windows PC.

The new design is industrial and classic Shimano. Everything looks chiseled out of space materials. The muted dark grey color is welcomed on any road bike build and I quite like Ultegra’s looks. And, more importantly, these updates make setup and maintenance much easier than Shimano Ultegra R8000 Di2.

The test groupset featured the compact 50-34T chainring and 11-34T cassette for that magical 1:1 wünder-gear. For gravel or long, steep climbs, that low gear comes in handy. On the steepest gravel and singletrack pitches, you are left a little short of proper gravel gearing like you’d find on GRX or SRAM Rival XPLR AXS. Again, that only comes into play when riding Ultegra R8100 on steep gravel pitches and I was still able to climb anything on the menu using a little extra muscle power. For just about every road climb, the 34/34 combo will get there with ease.

When climbing up road pitches, all shifts are smooth and predictable — with gradual steps between each gear. I did find the front derailleur to be occasionally slower to shift than the rear. But, that rear derailleur is a thing of beauty in concert with the semi-wireless shifters. Moving up or down the cassette one gear at a time or consecutively were always met with Japanese precision — no matter how much torque you were delivering. Feathering your way up any climb or finding just the right gear for that fast group ride will not be a problem.

Shimano has earned accolades for the shape of their hoods and I can attest that both Dura-Ace and Ultegra’s hoods are masterfully-comfortable. I can wrap my hands around the throat and adeptly maneuver the bike wherever I wanted to go. The brake levers are easily-reached while perched in the hoods or drops, but are optimized for the most power from the drops. Compared to the leverage point on GRX units, there is a considerable lack of power from the hoods — again something that comes into play on rough roads and gravel.

While the shift buttons are larger than the previous-generation, they are still challenging with winter gloves on. Nothing stacks up against SRAM when it comes to all-weather shifting. But, up or downshifts are smooth and responsive and I love that the brake lever is built just for braking and not for shifting too (as it is with Shimano’s mechanical levers). Their Servo Wave technology allows for wider-spread pads and rapid pad closure with the initial stroke. As a result, brake rotors are rub-free and deadly silent. However, with a 160/140 rotor combo (as tested), I was left wanting when I needed a fistful of brakes.

Shifting precision did take a hit on rough terrain. Without a clutch, the chain does wave wildly. It’s nowhere near as bad as derailleurs of yesteryear, but without a clutch, the Ultegra Di2 derailleur allows the chain to slap on the chainstay and reduces the otherwise-precise shifting.

The Good:

• Reduced wiring complexity with wireless shifters
• Feel of the hoods is outstanding
• Great shifter buttons and overall action
• Smooth, quiet braking
• Connectivity and updates are much improved over prior-generation Di2
• Remains an awesome choice for even the most demanding riders
• Power meter options available

The Bad:

• Without a clutch, chainslap is a reality on rough terrain
• Your existing Di2 charger is now obsolete (but simplified)
• Shifting with winter gloves remains challenging
• Brake leverage is really only optimized from the drops

The Bottom Line: Shimano Ultegra R8100 Di2

Unintentionally, the Shimano Ultegra R8100 Di2 kit fell into my lap on a gravel bike. While it’s still not my ideal gravel groupset, it performed better than expected on the roughest terrain. In more road-specific terrain, the rear derailleur shifted with the legendary precision that Di2 I know and love. For summer riding, the shift buttons are easily-actuated and I was beyond happy with the overall performance. Braking power was best from the drops and I’d suggest leaving the 140mm rear rotor to the pros and getting a 160mm on there.

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