The release of a new XTR group has happened just seven times in the platform's 25-year history. And for its first three generations, it set the bar for grading every fancy, expensive, shiny (or dull) component in hopeful competition. Then, in XTR's fourth generation, right around when SRAM introduced the first two-ring-specific drivetrain, Shimano found itself in what would be a decade-long game of catch-up. But we're not here to dig that up. We're here to find out whether this generation, M9100, has made that game any closer.
Shimano offers multiple drivetrain configurations in the new XTR, but we tested the one that takes direct aim at SRAM Eagle: the 10-to-51-tooth 12-speed. That 51st tooth isn't there to give Shimano one more than SRAM has. None of us noticed it anyway. It's there because, when Shimano mapped out its shift ramps, using a 51-tooth ring made the best map. That, we noticed.
Shifting 9100 was an altogether new experience for us, if you look at what actually happens when you shift. It's an ugly process. For a moment, the chain hovers diagonally across multiple cogs when it's really meant to lock straight onto one. You wouldn't know that when shifting the new XTR. The only noise we heard from the chain was a gentile click that was as clean and crisp as that which came from the shifter. It felt more like a perfect stroke through a car's manual gearbox than derailing and re-railing a spring-loaded external chain. And remarkably, upshifting onto smaller cogs was nearly as clean. That's something none of us had ever paid much attention to on other drivetrains. Downshifts tend to be more critical than upshifts. But Shimano has always paid special attention to upshifts. XTR 9100 still features a double-upshift, something we forget about after long stretches on SRAM drivetrains. And that double-upshift got refined for this generation. That second click takes a little more effort now, lessening the chance of an accidental double shift. Overall, we found upshifts to be quicker and quieter than we thought possible. And we could make them under more load.
Each of us who rode the new XTR has been riding for well over 20 years. Properly timing that split-second of relief we give our drivetrain during a shift is as natural as breathing, and nearly as crucial. But 9100 encouraged us to break that habit. Thinking like a racer for a moment, we could imagine the advantages of uninterrupted acceleration while upshifting after finishing a climb or a techy section. But that's mostly just a novelty to us non-racers. It was downshifting under load that really gave us goose bumps.
Those clean and crisp shifts were just as clean and crisp if we made them while hammering uphill. It behaved as though that was how we were supposed to shift. And really, we found no end to it. Surprise shifts, slow speed, high speed, it would barely complain until we were in such the wrong gear that we didn't have the momentum to save the moment anyway.
Accompanying the silence of the shifts is the 'Scylence' of the freehub. The hub's ratchet rings are separate while coasting and only connect while pedaling. It's the kind of thing we couldn't appreciate until we experienced it. Now that modern bikes are better at eliminating chain and cable rattle, eliminating freehub noise was the final frontier … almost.
The four-piston XTR brakes still feature pads with aluminum heat-sink fins. And they still rattle. In fact, the remarkably quiet 9100 drivetrain got all but one of our testers to start noticing the pad rattle. Luckily, Shimano still offers finless pads.
The rest of the brakes drew no complaints. The new clamp position widens the bracing surface of the lever body against the bar. It's hard to say that lent them more power, though. Shimano's four-piston brakes have never been short on power. But we did notice its onset was more predictable without that slight bit of flex. Throw in the wider lever blade, and we felt the brawn of a SRAM Code brake with the easy-access power of classic Shimano. We even appreciated the lever's hardware itself with its easy and infinite shifter position adjustment and double-hinged clamp.
The overall finish of 9100 is 100-percent XTR. It's as jewelry-like as ever, down to the forged alloy crankarms that don't require clumsy plastic boots to keep them safe. Or the forged rear cogs that will no doubt stand up to aggressive shifting better than SRAM's CNC'd construction. The new 9100 is true to Shimano's approach to design. Every piece is meant to work in balance with every other piece. Until 9100's concepts trickle down to XT and SLX, Shimano won't quite be a rival to SRAM, but when that happens, a similar and much-needed balance might return to the industry itself.