A Summer Spent Pedaling Aboard Shimano XTR 12-Speed Group Set [Review]

I put some long miles on Shimano's flagship 12-speed mountain bike group over the summer and it has lived up to the hype.

A pile of small blue and black boxes arrived at my apartment in June, brimming with new Shimano XTR M9100/9120 series bits to mount up and test out. I paused the article I was feverishly typing and lurked away into the basement to get the components bolted to my daily driver — a beautifully hand-crafted Ancillotti Scarab Evo 29. Well, all but the hubs that is. I paid a friend who has far more patience than I could muster to build those into a set of alloy DRC Bigfoot rims with DT Swiss Competition spokes and purple alloy nipples.

The drivetrain and brakes took just over an hour to install, and my buddy had the wheels tensioned and true the following day. In under 48 hours, my bike went from a random assortment of Shimano XT, SLX, and Saint parts paired with Rotor cranks to a comprehensive build, designed to function in unison. I was left to simply pedal it up the hill, and have done so roughly every other day since. Here are some thoughts and considerations on the blingy 12-speed XTR gruppo.

Shimano XTR Micro Spline hubs

I’ll begin in the center of the wheel because when I received these components there was no way to use this new drivetrain without hubs from Shimano, DT Swiss, or Industry Nine that have a proprietary Micro Spline freehub body. Fortunately, Shimano has since opened up its Micro Spline design license to any hub company that cares to ask and the offering of compatible wheels is steadily growing.

Both front and rear Boost hubs have functioned flawlessly through out the summer and the now saturated fall months. I haven’t adjusted the preload tension on either hub, as both are wiggle-free and spinning circles like new. Shimano maintained their loose ball bearing “cup and cone” design with these latest hubs, which allows riders to easily rebuild them without purchasing a costly pile of bearing removal and press tools. Fortunately, the bearings feel smooth as water, and won’t need a service for at least another few months of gyrating in the forest.

The term “degrees of engagement” refers to the amount of forward movement required to engage the pawls in a hub’s freehub body. With a slightly broader 7.6° of engagement in the XTR freehub I expected the wheel response to feel somewhat baggy on technical climbs when power transfer from the crank to the soil is key.

Well, this hub-snob has been proven wrong. I thought I needed über-tight engagement characteristics similar to the Industry Nine Hydra hubs, but the XTR hubs never once left me slamming a foot into a rock when I needed them to engage like some hubs tend to. While I would always prefer faster engagement, the XTR freehub handily does the job.

Shimano XTR M9120 Cranks and 32t direct mount chainring

Shimano’s XTR M9120 cranks look like they were forged in a city of traditional swordsmiths — and they were. My goofy duckfooted stance and propensity to clang against rocks have wiped off most of their perfect satin glow, leaving them looking like the well used party tools that they are.

For the sake of clarity, the M9120 cranks have a slightly wider Q-factor (stance) than the M9100 version and are otherwise identical. In all cases (save the derailleur), the M9120 is the burlier trail/enduro version of the XTR M9100 series.

With their new direct-mount chainring and tool-free preload adjustment, these are the most simple cranks Shimano has designed to date. I opted for a base model Shimano bottom bracket because I genuinely dislike the smaller bearings in the XTR external BB, and the proprietary plastic tool required to install or remove it. With the BB inserted and greased, simply insert the driveside crank and spindle, tighten the 8mm hex key on the non-driveside arm to spec, and remove any play in the cranks by hand tightening the preload adjuster. Voila, that’s it. No silly plastic preload bolt or pinch bolts to mess with. I haven’t paid an iota of attention to these cranks since tightening them in the frame, and like the hubs, they remain smooth and silent.

So damn simple.

Given the broad range of the gruppo’s 10-51t cassette, I chose to install the largest chainring that would fit on my bike. With a 51t pie-plate on the spinny side, there would be no trouble climbing in any place where I could find energy and grip. The 32-tooth ring sits a few millimeters from my chainstay and has performed well throughout the test. I did manage to eject the chain a few times when it was exceptionally muddy out and the chainring teeth packed up with damp soil, but that nonsense was quickly remedied by installing an upper chain guide. I also “reshaped” the chainring on a rock during a multi-day enduro, to the point that the chain was catching on some bent teeth. That too was promptly rectified by truing it with a broad crescent wrench, though I will replace the ring so it doesn’t shorten the chain’s life. The chain continues to function flawlessly, despite kissing the same rock, but once the chainring is swapped it will likely be time to wrap the cogs in a fresh chain.

Shimano XTR M9120 Trail Pedals

My talented colleague, Matt Miller, wrote a full review of the XTR M9120 Trail Pedals for your reading pleasure. I will only add that this set has functioned flawlessly, and retains the thematic thread of the above components: liquid smooth and backcountry silent.

Shimano XTR Drivetrain

Now for the clicky bits. Rear shifters for the group set can be mounted with a traditional 22mm bar clamp, or paired seamlessly with the brake lever. According to Shimano, “The new I-SPEC-EV designs give 14mm of lateral sliding range and 60 degrees of rotational positioning so riders can find their most ergonomic hand position on the shifters and levers and have clutter-free handlebars.” Additionally, the brand has designed a dropper post lever that pairs directly with their left brake mount, as does the latest V2 remote from OneUp Components.

I’ve heard rumors that there is also a front shifter that integrates similarly, along with a double-crankset and front derailleur, though I’m not sure why. With a 10-51t cassette, there isn’t much justification for the added complications of a front mech. Furthermore, the double chainring setup limits the drivetrain to its smaller 10-45t cassette.

The shifter’s thumb and forefinger paddles are covered in soft rubber to provide grip in the rain and for sweaty hands, which is a thoughtful touch. Given the lever ergonomics and overall light action, I have been left to think about anything but shifting. My personal favorite element of the XTR shifter is the ability to upshift with either my thumb or forefinger, depending on the angle of my hand. The “go fast” lever swings both ways, allowing the rider to click into a higher cog regardless of their hand and body position.

Out back, the old gear hoppin’ parallelogram has grown far sleeker, lighter, and admittedly better looking. Its enlarged 13t pulley wheels work in tandem with the Shadow RD+ clutch to keep the chain where you want it and minimize the blather and drivel of chain slap. In addition to slimming down and accepting a wider cassette range the M9100 derailleur’s carbon fiber outer cage has swollen into quite the robust rock deflector. Note that the fiber along the trailing edge of mine is splintering from countless stone encounters, but remains fully functional.

I am hopeful that Shimano will rethink their clutch design at some point. This one is performing precisely as advertised, but the last few 11-speed derailleurs I have used needed their clutches rebuilt a little too often for my taste. Furthermore, having a button to lock the derailleur open (tensionless) when you want to remove the rear wheel is a pretty sweet feature that’s missing here.

The aim of these giant modern cassettes is to expand the overall range of your 1X drivetrain while adding cogs to keep the space between gears reasonable. Hence 12-speeds. The amount of time and attention Shimano gave to ensure that this drivetrain shifts precisely and dependably is most evident when you stand up and shift while applying max power to the cranks. If the cable tension is properly adjusted, you won’t hear the loud pop and clang reminiscent of other brands’ drivetrains. It will simply change gears. Like electronic drivetrains, you can shift whenever you like without worrying about binding the chain or snapping teeth from your cassette. To ice the cupcake, this collection of alloy, titanium, and steel cogs is wicked light at 368 grams.

On my first few outings with the 12-speed drivetrain, I had the sense that the gears were too close together. I found myself consistently grabbing two gears at a time in either direction and while I was stoked with how quiet and quick the shifting felt, I wasn’t immediately sold on the 12-speed range. Then I went on some longer pedals with friends that included significantly more elevation gain. I quickly saw the advantages of the tighter cog ratios when the trail’s slope tilted to a grunting pitch.

I tested a 12-speed SunRace cassette with the XTR drivetrain while reviewing a set of wheels that didn’t have a microspline freehub. While the SunRace cluster did work, and it will allow you to run a wider variety of wheels, the drivetrain’s performance was undeniably diminished in comparison to the dialed and integrated feel of the M9100 cogs. Fortunately, there are now XT and SLX cassettes available that should perform swimmingly if you want to save some cash and maintain crisp shifting, though they too require a Micro Spline freehub.

The lever clamp has shifted inward, paired with a handlebar brace to reduce flex in the lever body.

Shimano XTR M9120 4-piston brakes

There are a host of similarities between Shimano’s famed Saint brakes and the new XTR 4-piston brakes. They are a bit like fraternal kitten twins, with similar guts and different fur markings and body sizes. Both use a pair of 15/17mm ceramic plungers to engage the pads, and the same size master cylinder to push all the mineral oil around. The parallels largely end there, as the XTR slowing system is lighter and sleeker, with more modulation and less brute strength than the Saint setup.

The lever feel is akin to any other Shimano brake, though the XTR M9120 offers a more refined modulation than the Saint or the earlier Shimano XT 4-piston models. SRAM fans will likely appreciate the amount of feathering these brakes allow, and those feathers are backed with a potent amount of stopping power. On descents that reach into the 20-30 minute party-range, the M9120 system performs with exemplary dependability and unwavering power. Every time I pull the lever I know what I am going to get and when, and that steadfast reassurance is what I need to let go a little longer.

At one point I felt there was no reason to run anything but Saints on my daily-driver, but these new 4-pots have shifted that thinking. Though they are a modicum less powerful than their DH cousins, they have provided all the stopping power I needed over a summer of racing and riding unknown tracks. Here again, Shimano now offers XT and SLX models of these stellar mountain bike brakes, so more riders can afford to add a new pairs of plungers to their bikes.

As I mentioned, I didn’t have any surprises with these brakes fading or feeling spongey on long descents. I have not had to bleed them since the initial install service, and even swapped pads without opening the mineral oil bottle. I did rapidly blow through the resin pads that come installed in the calipers, and promptly replaced them with the metal material that I prefer.

Space ship aesthetics anyone? Shimano’s older style of 4-piston (Saint/Zee) pads will also work in the M9120 calipers, though their tall profile looks a little awkward. The proper replacement pads for the new 4-pots are N03A Resin or N04C Metal.

The Ice-Technologies Freeza rotor design is said to reduce weight and dissipate heat more efficiently. According to Shimano, “The 140 and 160mm rotors shed 5 and 10g respectively, whilst the 180 and 203mm rotors were 20°C cooler during testing with the 203mm rotor also saving 30g (vs RT99) in weight.” This winter we will be heat testing a stack of different rotors to find out how much all of these fin design and material mixes affect heat dissipation. Stay tuned.

In summation

So who is this Shimano XTR gruppo made for? Well, the “R” in XTR stands for race, and that is clearly one place these components will shine brightly. For folks who want their trail or enduro bike kitted with components that optimally balance weight and peak performance for a dependable ride, this gruppo should be one of the few in consideration. Additionally, if mountain biking is life for you, and your pockets are packed with cash, having the most advanced mechanical shifting and hydraulic braking systems that Shimano offers is a sweet treat. If you truly live and work so that you can mountain bike, you deserve the best gear and based on the components I have tested, this is it.

For those of us with tighter bike budgets, the latest Shimano XT and SLX 12-speed gruppos are also fantastic. Shimano clearly learned what they know by watching XTR.

Component weights

Depending on parts selection, every build will be different, but I’ve outlined mine below to give an idea for weights. All told, my drivetrain, pedals, and brakes add 3,134g to my overall bike build.

Pedals w/o cleats397g$179.99
32t chainring*67g$129.99
Cassette 10-51t 368g$379.99
Uncut chain 268g$64.99
Long cage derailleur 243g$259.99
Shifter & cable 126g$129.99
Rear hub  236g$329.99
Front hub 124g$179.99
170mm crank, 34t ring515g$549.99
180mm rotor & lockring139g$84.99
203mm rotor & lockring152g$129.99
Rear brake uncut 287g$325.99
Front brake uncut 279g$325.99
Rotor lockring*10g
Prices at time of publication

We would like to thank Shimano for sending the XTR group for review.