Hate to spoil it with the fancy title, but Shimano had run out of promises. The mountain bike community has long been waiting for Shimano to drop the front derailleur, stop fooling around with electronics, and give us a wide-range 1x drivetrain that could challenge SRAM's near takeover of the global trail bike market. The time to play catch-up had long passed. Shimano needed to knock XTR out of the park. I'm pretty sure they just did.
To discover why I think the new XTR is so right, let's recap how it got so wrong. Shimano's overarching rule for XTR is that it is designed to be a no-compromise racing ensemble. Well, that fell apart when long-travel trail bikes that catered to capable riders became the dominant segment of the sport. Shimano responded by diluting XTR into a very expensive pile of make-everybody-happy components that could be configured to fit almost every mountain bike genre, from bike packing to World Cup XC. Somehow, in that flurry of engineering, they made everything but
the wide-range 1x drivetrain that the long-travel trail bike crowd were begging for. The previous generation XTR performed admirably for what it was, but to move forward, euthanasia was Shimano's only recourse.
New Cassette and Driver Micro Spline:
Enter XTR M9100
Shimano put XTR back on track with a complete redesign from top to bottom and, more importantly, reaffirmed the group's commitment to racing. The new group is numbered M9100, and it is configured in two distinct versions: one for cross-country and one for enduro.
The scope of improvements and innovations that are packed into the new M9100 ranges from minutia, like tiny shoulders formed inside the chain links, to a radically different freehub ratchet with a clutch that completely disengages it while coasting. So, let's dive right into the tech, beginning with 12-speed.
The most anticipated news was 12-speed XTR, and second to that, whether or not Shimano would adapt its cassettes to SRAM's XD driver or invent a new freehub mechanism that would allow the use of clogs smaller than 12 teeth. The answer is the latter: "Micro Spline." Shimano's first aluminum cassette body, and it is compatible with... nothing. Shimano says that the chances of licensing the XD driver were near zero and that Micro Spline gave them more options to optimize their cassette.
Scylence freehub system:
With 23 deep, rectangular splines, Shimano says they can forge the Micro Spline freehub body from aluminum without risking the deformation and galling that conventional aluminum cassette bodies suffer. The inspiration came from Shimano's Center Lock brake rotor interface, and it allows the use of stand-alone cassette cogs, in conjunction with a new lightweight spider system.
Will Shimano license its Micro Spline technology? Yes and no. The official word is that only DT Swiss will have access to Micro Spline and beyond that, Shimano has no current plans to license the system. Before you sprint to the comment section, consider that Shimano has used the same basic freehub system since the dawn of index shifting. It's about time for a change. Shimano will also offer a range of hubs (more about this later) with non-series options for OEM customers.
In some ways, it resembles a DT Swiss Star Ratchet system, but it's a whole new animal. For starters, the teeth completely disengage while coasting. As the name suggests, the system is silent - and that may take some getting used to. For well over a century, the chatter of spring-loaded freewheel pawls has defined the bicycle from all other modes of transportation.
Shimano's Scylence freehub: The green ratchet wheel indexes into the hub shell. The yellow ratchet wheel screws into the short spiral segment on the left side of the blue Micro Spline body. Pedaling torque forces the green and yellow ratchet wheels together. When coasting, the spring between the wheels disengages them completely, so the system runs quietly in both modes.
The Micro Spline driver has a series of spiral grooves on the back side that physically pull the star ratchet plates together. Pedaling torque engages the freehub ratchet, not flimsy springs, so the hub is locked in place as long as you are applying pressure to the pedals. A coil spring between the ratchet plates disengages them and keeps them separated while coasting. The Scylence freehub system provides 7.6 degrees of engagement. Its components are simple, robust and, unlike other silent freehubs that use roller or sprag clutches, its ratchet mechanism minimizes radial loads, so the hubs can be made much lighter weight.
Hyperglide+ 12-speed cassettes use an aluminum spider to secure the eight largest cogs. The three black sprockets are aluminum, the five grey ones are titanium, and the final four cogs slide directly onto the Micro Spline freehub. Hyperglide+ cassette:
Shimano pioneered shifting ramps to keep the chain engaged with both cogs while shifting, but until today, those ramps only worked when shifting to the next larger cog. The clunking and clanking sounds that accompany each shift towards the ten-tooth cog will attest to that. Shimano's new Hyperglide+ cogs have ramps in both directions, so shifting to the next smaller cog is quicker, seamless, and should minimize interference with your butter smooth pedaling cadence.
Shimano added down-ramps to XTR cassette cogs for seamless shifts from larger to smaller sprockets.
Shimano will offer three cassettes for XTR M9100. Two 12-speed and one 11-speed. The most popular 12-speed cassette will probably be the wide range 10 by 51 tooth model. That one-tooth advantage over SRAM Eagle is probably there for bragging rights, but it could be defended as an "adjustment" to give 29-inch wheel riders the same low gear as they would experience riding 27.5 with a 50 tooth cog out back. Speculation aside, Shimano also offers a 12-speed Rhythm cassette that tops out at 45 teeth, with the benefits being more closely spaced shifts in the lowest three gears.
11-speed? In an unexpected turn of events, Shimano developed an 11-speed cassette that shares the same gearing as its 10 by 51, but with the 51 removed. The reasoning was that, when asked, Shimano's sponsored racers (both from enduro and cross country), maintained that they didn't need the 51, and were unwilling to carry the burden of the extra cog. Riders who commit to XTR 11-speed can choose a special hub that spaces
Hyperglide+ Gearing Options:
10 x 51 Wide Range:
• 510% gear range
• 10, 12, 14, 16, 18, 21, 24, 28, 33, 39, 45, 51
• 367 grams
10 X 45 Rhythm Step:
• 450% gear range
• 10, 12, 14, 16, 18, 21, 24, 28, 32, 36, 40, 45
• 357 grams
10 X 45 Lightweight:
• 450% gear range
• 10, 12, 14, 16, 18, 21, 24, 28, 33, 39, 45
• 310 grams
the hub flange 4.7 millimeters to the right to help even out the spoke tension, but there's no going back to 12 speed, because the 12th cog will touch the spokes. 11-speed cassettes are backward compatible with 12-speed hubs. Adding up the weight benefits of one less aluminum cog, a couple of missing chain links, and by taking advantage of XTR's mid-length rear derailleur cage option, finicky pros can save 80 grams.Beam Spider Technology:
Shimano's modular cassette design is competitively lightweight and very easy to install. Shimano pegs the 10 x 51 12-speed at 367 grams, with the 11-speed 10 x 45 at 310 grams. (SRAM's claimed weight for an XX1 12-speed cassette is 352 grams.) Most of the cogs are slender rings that are riveted to a lightweight aluminum spider. The first three cogs are aluminum, followed by five titanium cogs. The smallest four cogs are steel and mount directly to the Micro Spline driver. Shimano says they use secret, long-wearing surface treatments on all of the cogs, and even if you do wear out a couple of sprockets, you won't have to replace the entire cassette to freshen it up. Hyperglide+ cassettes are retained with a threaded cap using Shimano's existing spline tool.Bonded-Aluminum, Direct-Mount Crankset
Shimano certainly has the technology to manufacture a carbon crankset - and they have done so - but their testing showed that it was aluminum that came out on top in the strength, weight, and durability contest. The 9100-series XTR cranksets feature a direct-mount spline instead of the four-bolt spider, which is lighter weight and much better looking. The non-drive side arm no longer clamps onto the tubular steel axle. The new interface is still splined, but the crankarm also has a more conventional locking taper. The left arm is fixed by an Allen key, is self-extracting, and features a bearing preload adjustment dial.
Bonded technology: Like Dura-Ace road cranksets, the new XTR crankarms begin as two pieces: an aluminum forging that integrates the pedal threads, bottom bracket axle interface
Crankset Features & Options:
• Direct-mount chainring
• Bonded, hollow aluminum crankarms
• Tubular steel axle
• Bearing preload adjustment dial
• 168 or 162mm Q-factor options
• One 52mm chainline for 142mm or Boost-width hubs
• Dual-chainring option (28 x 38t)
• Narrow-wide chainrings (30, 32, 34, 36, 38t options)
• Left arm has locking taper and one-key release
• Weight: TBD
and chainring mount is bonded to thin, stamped-aluminum outer shell. The result is a stiff, hollow structure that should take a beating without long-term durability concerns. No word yet on available crankarm lengths, but we expect to see 165, 170, 175 and 180-millimeter options. One chain line and two Q-factors:
Shimano XTR cranks support both Boost 148-millimeter and non-Boost 142-millimeter axle widths with one 52-millimeter chain line. The key to this simplification is a modified narrow-wide chairing tooth profile, in combination with shaped chain plates that, reportedly, run more quietly and with less friction at exaggerated angles. In order to mirror road bike Q-factors, Shimano offers two different cranks: M9100 with a 62-millimeter Q-factor for cross-over roadies and M9120 with a 68-millimeter Q-Factor for the rest of us. Some Boost-width frames will not be compatible with M9100 cranks. Direct-mount chainrings:
Shimano may have been the last to see the light on direct-mount chainrings, but it's great to have them on board. The interface is a simple spline, similar to Centerlock brake rotors, but the threaded stainless steel retaining ring is much thinner. The retaining ring's spline drive is the same as Shimano's external bottom bracket cups, but Shimano recommends that installers use a dedicated tool that slips over the bottom bracket axle to prevent damage to the ring. The tool will be included with aftermarket cranksets.
Shimano's modified narrow-wide chainring teeth fit like a ball and socket into the chain's radius-profiled inner plates. Reportedly, the chain runs quietly at extreme angles.
As mentioned, Shimano has done some modifications to the well-proven narrow-wide tooth profile, most of which are targeted at silencing the chatter created by the chainring teeth as they mesh with the chain while it is riding at the extreme ends of the cassette. Chainrings are aluminum, and the options are 30, 32, 34, 36 and 38 teeth for 1x drivetrains. A 2x option?
Not a lot of people want a front derailleur these days, but if you do, Shimano offers a two-chainring crankset with a 28-tooth low gear and a 38-tooth big ring. The smaller sprocket is fixed to the 38-tooth direct-mount chainring, so if your frame accepts a front derailleur and you decide in the future that you need to go back in time, you can retrofit a double to your 1x crankset. New Shift Lever and Rear Derailleur
Shimano has a stellar track record with rear derailleurs, so I'm confident the new XTR's shifting performance will continue that legacy. XTR M9100 has three options: A long cage SGS changer intended for the 10 x 51 and 10 x 45 tooth cassettes; a mid-cage GS changer that can be used for either the eleven speed or twelve speed, 10 x 45-tooth cassettes, and a special rear mech' for Shimano's 2x drivetrain, labeled RD-M9120, that also tops out at 45 teeth. Shimano notes that the mid-cage GS option also offers more ground clearance for 12-speed riders who have the legs to push a 45-tooth low gear.
Highlights of the latest XTR rear derailleur are: reduced pulley tension in the lowest gears for less noise and friction; larger, 13-tooth jockey pulleys; a rubber cushion has been added to prevent the chain from buzzing the cage at full chain wrap-up; and the mechanism has been further trimmed to tuck it away from harm.
Upgraded shifters: Shimano responded to the many athletes who have been doctoring their shift levers with friction tape by adding a hydrophilic rubber pad on the thumb lever. Apparently, shifting effort has been reduced by 35 percent and shifting is 20-percent quicker. The I-Spec direct mount has been redesigned too (not backwards compatible with previous XTR), with a wider range of adjustment. I-Spec EV features 60-degrees of rotation and 14-millimeters of side-to-side adjustment. XTR 9100 shifters will also be sold with a discreet clamp. For those who choose the 11-speed cassette, the shifting pod has a switch that limits the 12-speed mechanism to 11. To make single versus multiple shifting more intuitive, the thumb lever's second click has been strengthened.
2x drivetrain customers will receive Shimano's new "Rapifire Mono" shift pod for the left side of the handlebar, which uses only one lever to shift up to the big ring and release to the small sprocket. News is that the Mono lever is more intuitive to use and that's fine with us.Drivetrain Prices and Weights
J-Bend and Straight-Pull Hubs
XTR M9100 hubs are available in three configurations, all in both Boost and non-Boost axle widths: M9110-B hubs have J-bend spoke flanges, and M9110-BS hubs feature straight-pull spoke flanges. Both styles require that the drive-side flange be slightly larger in diameter to clear the bulge necessary for the Scylence freehub ratchet-clutch. Because the straight-pull flanges can be drilled at different depths, wheels built with those hubs use same-length spokes. J-bend hubs, however, will require different-length spokes. The new Micro Spline design allows for larger-diameter axles (inside the hub), which should boost lateral stiffness.Wide-Flange rear hub:
Riders who opt for XTR's 11-speed cassette will get some benefit from the dedicated wide-flange rear hub. The drive-side flange is moved outwards 4.7 millimeters, which reportedly boosts wheel stiffness and helps to balance spoke tension. Wide-flange is only available in the J-bend option and Boost, 148mm axle width. As a side note, all XTR hubs use Center Lock brake interfaces.Non-series options:
As mentioned earlier, Shimano will offer Boost-width hubsets that do not carry the XTR logos with both straight-pull and J-bend flanges. Non-series options will feature Scylence freehubs, and the J-bend style will use symmetric hub flanges.Hub Prices and Weights
New Levers: The new XTR brake levers have moved the handlebar clamp inwards by about 25 millimeters, which creates space to tuck a dropper post lever or a suspension control inboard of the grip. Shimano says that the clamp placement saves weight without eroding strength. The lever blade is carbon and two versions will be offered. The lighter weight XC lever will not share the Enduro model's fast-acting Servo-Wave device. The XC master cylinders are magnesium, while the Enduro model's are aluminum.
Better modulation and more power: Shimano has been criticized for its abrupt braking action, so the new XTR stoppers have been re-tuned to hit softer and deliver a very linear feel as the lever is brought
Brake Features & Options:
• Lever clamp moved inboard
• Magnesium lever body (XC)
• Carbon lever for XC, aluminum for Enduro
• 2-piston XC caliper/4-piston Enduro caliper
• Enduro pads are interchangeable with Saint
• Enduro brake matches Saint power rating
• Compact cooling-fin design (Enduro only)
• New I-Spec EV direct-mount interface
• XC system weight: 204 grams (lever, hose & caliper)
• Enduro system weight: 277 grams
• New two-piece rotors: 140, 160, 180 & 203mm
to maximum power. Braking power has been boosted for both the XC and Enduro versions, with the Enduro brakes receiving the same power rating as Shimano's aging Saint DH brakes. Enduro levers have been tuned for faster engagement and a shorter free-stroke as well.
Brake Prices and Weights
Two calipers: The new two-piston XTR XC caliper has been trimmed for weight savings with a smaller brake pad and a re-routed hose exit that does not require a banjo fitting. Ice-Tech fins are no longer an option. Four-piston Enduro calipers use a compact cooling fin design and retain the banjo fitting. Enduro brake pads are interchangeable with Saint, which should prove helpful for racers who are scrounging for spares in the pits.
Rotors: The full name is "Ice Technologies Freeza" construction, and it describes Shimano's combination of a sandwiched, stainless steel and aluminum brake rotor that features aluminum cooling fins. The Center Lock aluminum spiders are new, with a more rigid star shape, and the cooling fins are now black to shed heat faster. Sizes are: 140, 160, 180 and 203 millimeters.
Shimano refreshed both XTR pedals with enhanced contact points across the middle of the platform for a wider contact area. That was facilitated by raising the aluminum body slightly where the sole of the shoe contacts the outside faces on the pedal. To make it easier for Boost-spacing riders to transition from road bikes to mountain bikes, Shimano will offer the cross-country SL pedals with a shorter, 52-millimeter axle option that brings the Q-factor in line with their road racing pedals. Standard XTR SL pedals will retain the 55-millimeter length. SL pedal weights are 310 grams (52mm axle) and 314 grams (55mm axle). A one-millimeter cleat spacer is also included to fine-tune the shoe/pedal interface.
XTR Trail pedals received a similar treatment, but won't get the 52-millimeter axle option. The platform has been lengthened in the rear and widened across the middle with a raised platform to better stabilize the shoe. The one-millimeter cleat spacer is also included. Weight is pegged at 398 grams.
Two New Toys
Adjustable top guide: If you've followed EWS enduro or World Cup cross country, you've probably seen a number of demi-style chain guides adorning the top of the chainring on 1x drivetrains. Shimano devised its own top guide. Suitably named, the SM-CD800 Chain Device can be obtained in three configurations to fit Shimano's high or low direct-mount front derailleur bosses, and there is one to fit ISCG-05 mounts. An adjustment dial lets the rider fine tune the guide to prevent chain rub without tools.
Cable style remote dropper lever: Those who insist on a full Shimano cockpit can now purchase the sharp-looking but not-quite-revolutionary SL-MT800 Seat Post Lever. Available only in I-Spec EV direct mount, it features ball bearing supported light action and a rubber padded thumb paddle. The cable is fixed at the lever, which means it can be easily configured to operate almost all cable-actuated dropper posts.
XTR 9100 will be available Fall 2018. A long-term review is in the works.