It took much longer than anticipated for Shimano to come out with a 12-speed mountain bike drivetrain, and even when they did release the details of the new XTR M9100 group it was still nearly a year before all of the components could actually be purchased. That meant there was a three-year span between the debut of SRAM's Eagle 12-speed gruppo and Shimano's entry into the ring, enough time that even diehard Shimano fans began to jump ship in search of more shifter clicks and wider range cassettes.
Thankfully, it looks like the amount of time between announcement and availability should be much shorter with the upcoming XT and SLX groups
, and, if all goes to plan, by the end of this summer riders will have a range of price points to choose from.
But let's focus on the XTR M9100 group for now, Shimano's flagship off-road drivetrain.
XTR M9100 Details
• 12-speed, 10-45 or 10-51 tooth cassette (tested)
• Multi-release shifter
• Direct mount chainring
• Hyperglide+ cassette and chain technology
• Requires MicroSpline freehub body
At this point, the details of the XTR M9100 drivetrain have been discussed in extensive detail multiple times, including a First Look article
and an First Impressions article
. But if you missed those, here's the quick rundown. Cassette / Chain:
The 10-51 tooth cassette is the heart of the drivetrain, with three aluminum cogs, five titanium cogs, and then four steel cogs to finish things off. The cassette and the hollow pin chain are shaped specifically to allow shifting to be performed at any time, even under load. The gear steps are: 10, 12, 14, 16, 18, 21, 24, 28, 33, 39, 45, 51. There's also a 10-45 tooth cassette for riders who don't need such a wide range and would rather have closer spacing between each shift. The cassette requires a MicroSpline driver body, which has 23 rectangular splines that allow for the use of a multi-part cassette with a 10 tooth cog. The cassette weighs in at 376 grams.Shifter:
According to Shimano, the M9100 shifter requires 35-percent less effort to activate, and shifting is 20-percent quicker. Both up- and downshift levers are textured to avoid thumb slippage, and it's possible to shift down two gears with one single push. Weight: 127 grams.Derailleur:
The derailleur uses 13-tooth jockey wheels and retains the adjustable clutch mechanism found on Shimano's prior derailleurs. Weight: 242 grams.Cranks / Chainring:
You may have noticed that the cranks shown in the title image look a little different - that's because they're the M900 cranks, which have an XTR direct mount chainring mounted to the new XT cranks. Production models of top-tier XTR M9100 cranks only recently became available; those cranks are still aluminum, but forgo the familiar two-bolt crankarm mounting interface, and are approximately 80 grams lighter than the 595 gram cranks (with ring) tested here.Installation
Every time I install a 1x drivetrain, I take a moment to pause and appreciate the fact that front derailleurs have almost completely disappeared from the mountain bike world. I spent way, way too many hours wrestling with those finicky things during my years as a mechanic, and the fact that many bikes don't even have a spot to mount one makes me happy. Yes, there is an XTR M9100 front derailleur, but I'm just going to look the other way and pretend I didn't see it.
With no front derailleur to fuss with, it's the rear derailleur adjustment that's the key step in the installation process. Shimano takes the win here vs. SRAM – they've thoughtfully printed a mark on the backside of the outer pulley cage that makes it incredibly simple to set the correct amount of B-tension, without the need for a separate plastic tool.
The cassette installation is simple, but don't forget to install the small, almost clear spacer that comes with the cassette. It's an easy thing to overlook or misplace, but it's designed to help prevent any unwanted creaking.Performance
When's the last time you really thought about when and where you shift during a ride? For most of us, shifting has become second nature – we're accustomed to shifting into an easier gear before a big hill in order to avoid shifting while pushing hard on the pedals, or, if that's not possible, unweighting the pedals slightly during a shift to prevent the chain and cassette from emanating any clunks and clanks of displeasure. Shimano's Hyperglide+ design makes that unweighting and pre-planning unnecessary – you can now shift whenever you want, and the chain will move up or down the cassette without any fuss.
I was skeptical at first, and all the years of practicing proper shifting technique made it hard to trust that bad things wouldn't happen when I decided to shift during the middle of an extra-steep climb. My fears were unfounded, though, and the chain went exactly where I wanted it to each and every time.
Want to quickly shift into an easier gear while you're pedaling hard out of a corner? Go for it. How about shifting into a harder gear in the middle of a sprint towards a hard-to-clear jump? Yep, that'll work too. For me, this is the most impressive feature of the entire drivetrain.
The only downside is that when I would hop on a SRAM-equipped bike I occasionally found myself shifting as if I was still on XTR, which caused a few clunky gear changes and some not-so-nice noises. I also missed the ability to drop down two gears with one push when I switched to a SRAM drivetrain It's a little thing, but with SRAM a double click is required, while with Shimano it's one single push.
As far as the actual shifter ergonomics and feel go, the XTR shifter requires a little more effort to push compared to a SRAM X01 shifter, but it is very distinct and precise, and shifts feel like they happen the very instant the lever is depressed.
I'm also a fan of the traction pad on the shift lever, a feature that came on several wet and slimy winter rides. That pad can be replaced but based on the limited amount of wear that's visible so far, I have a feeling that won't be a very common occurrence. Cassette Spacing
It wasn't too surprising when Shimano announced that their cassette had a 51-tooth cog. There's probably some science behind it, but I've got a feeling having a wider range, no matter how small, than SRAM's 10-50 tooth Eagle cassette was always the goal. I didn't notice any massive difference between riding with a 50-tooth gear and a 51-tooth gear – they're both easy enough to provide some welcome respite on super-steep climbs.
With the XTR cassette, it's only a 6-tooth jump to get to that 51-tooth cog, versus the 8-tooth jump on an Eagle cassette. That spacing difference is noticeable, and it makes it easier to maintain a similar cadence after making that shift. Durability
The entire drivetrain has survived the wide range of conditions I've subjected it to, and the amount of wear that's visible is in line with what I'd expect. The fact that the derailleur's clutch is adjustable and rebuildable is another point in Shimano's favor vs. SRAM. The non-series cranks are developing the usual rub marks; it's a little more noticeable on the black cranks compared to the actual XTR cranks, but either way, it's going to happen, especially if you ride in wet, gritty conditions. Does It Blend?
There have been a number of questions floating around in the comments section about the cross-compatibility of SRAM and Shimano components. Of course, neither company is going to recommend mixing and matching their components with a direct competitor's, but does that mean it doesn't actually work? Not exactly... It turns out that the cassette spacing and cable pull amount are close enough that mixing brands is entirely possible.
Not surprisingly, if you want the best shifting performance from an XTR drivetrain, it's best to use all of the components - chain, derailleur, cassette and shifter. The chain and cassette are specifically designed to work together, and if you use a different chain you aren't getting all of the benefits of the impressive Hyperglide+ shifting.
That being said, it's also possible to pair a Shimano XTR shifter and derailleur with a SRAM Eagle cassette and chain. You'll lose the ability to power through the gears under load, but you'll still be able to drop two gears with one push of the shifter, and have a serviceable and adjustable clutch, all without needing to buy a Microspline freehub body or an entirely new hub / wheel. The Weight Game
For all the gram counters out there, here's a handy chart that illustrates how XTR stacks up against SRAM's X01 drivetrain. Yes, SRAM's XX1 drivetrain will be a smidge lighter, but that's group is aimed more at XC racers and riders, while X01 and XTR have a broader range of intended usage. The biggest difference in weight comes down to the cranks and is due to SRAM's use of carbon vs. Shimano's aluminum. The actual XTR cranks (I tested the non-series cranks, which are technically XT cranks with an XTR chainring) will be lighter, but still not as light as SRAM. Shimano does take the win for the derailleur weight, coming in at 242 grams vs. 281 grams for an X01 derailleur, but that gain is partially erased by the slightly heavier cassette and shifter. At the end of the day, both groups are quite light, especially considering how much abuse they can withstand.
Incredible shifting performance, especially under load.+
Excellent shifter design, feel.
Gram counters will likely want lighter cranks.-
MicroSpline driver body isn't widely available yet.