Shimano XT and SLX go 12-speed: M8100 and M7100 MTB groups explained

by Dave Rome


Last year Shimano introduced us to the XTR M9100, the Japanese company’s first 12-speed mechanical groupset. With an extra gear, a clear commitment to 1x setups, a 10-51T cassette option, Hyperglide+ shift ramps, a new cassette spline fitment, and a wholly new rear freehub mechanism, this flagship mountain bike component series gave us plenty to talk about.

Shimano has now announced not one, but two, wholly overhauled mountain bike component ranges which feature a smorgasbord of trickle-down technology from XTR, bringing 12-speed Shimano shifting and associated updates to substantially lower price points. For insight into what these technologies are, please take a look at our detailed coverage of XTR M9100.

Shimano’s refusal to lay down for SRAM’s hungry Eagle is cool and all, but perhaps the biggest news is one related to availability. Shimano’s new XT M8100 and SLX M7100 will be on shelves within a couple of weeks, not months.

In this article, we’ll take a quick look at what new technology has carried over, what hasn’t, and the key differences between the new XTR, XT and SLX groupsets. For first ride impressions, head on over to Pinkbike for Mike Kazimer’s thoughts.


1x and 2x, Cross Country and Enduro

Just like the XTR M9100, the new XT M8100 and SLX M7100 are all about choice. Each offers a range of components tailored to match the differing demands of cross country, trail and enduro mountain biking. Enduro riders receive more powerful brakes and wider-spaced fitment options, while those at the cross country end of the mountain bike spectrum get a choice of 1x or 2x gearing.

Mixing and matching is a key feature with the new groups, and all M-series 12-speed components offer full cross-compatibility with each other. Simply pick and choose as you like. Additionally, there are components to suit a staggering number of industry “standards” including cranksets and hubs for regular (135-142mm), Boost (148mm) and SuperBoost (157mm) spacings.

While many of the features and technologies first seen on XTR flow downward, it’s fair to say that XT and SLX are a lot closer to each other than XTR is to XT.

Cranksets, cassettes and chains

The XT and SLX cranks use the same 24mm steel axle and double-pinch bolt attachment method as previous cranks – something that’s said to be a more economical choice to the 8mm hex retention bolt used on XTR M9100. The bottom brackets carry over from the previous generations unchanged. And as mentioned, both XT and SLX cranks will be offered to suit regular, Boost and new SuperBoost fitments with Q-factors of 172, 178 and 181mm respectively.

Featuring the same direct-mount chainring system as XTR, the XT crank is available with 28, 30, 32, 34 and 36T narrow-wide chainring sizes, and crank lengths of 165, 170, 175 and 180mm. SLX M7100-level cranks will only be available in 165, 170 and 175mm lengths, and with 30, 32 and 34T chainrings. XTR, XT and SLX chainrings are all cross-compatible, and so fitting a 38T XTR ring to the XT crank, or a 28T XT ring to an SLX crank is totally possible.

For those seeking a limitless 623% range, Shimano will continue to offer 2x gearing setups for both XT and SLX, just like it does in XTR. This includes just a 36/26T chainring combination to be matched with the closer-spaced 10-45 cassette and 2x-specific rear derailleur. There are a number of front derailleurs to suit common frame fitments and a simplified up-down “Mono” front shifter is available, too. Both XT and SLX 2x cranks are the same as their single-ring counterparts, available in regular and Boost chainlines.

One of the most polarising elements of XTR M9100 was the introduction of a new freehub spline design, dubbed Micro Spline. And where XTR launched with the Micro Spline fitment available to just Shimano and DT Swiss, that is (slowly) changing as more hub manufacturer names are added to the licensee list (such as Mavic and Industry Nine). Still, the controlled availability of Micro Spline remains the largest barrier to aftermarket acceptance of the new drivetrains, especially considering that SRAM’s specific XD-driver design is provided by almost every hub- and wheelmaker (except Shimano).

Both XT M8100 and SLX M7100 adopt the new Micro Spline design which allows for 10-51T and 10-45T cassettes. The former size offers a whopping 510% range from a single chainring, whereas the more tightly spaced 10-45T cassette can be used with either 1x or 2x systems. While it would be possible for Shimano to offer a non-series 11-51T cassette to work with existing freehubs (much like SRAM’s PG-1230 cassette), no such product has been made available.

New M8100 and M7100 chains share the same extended inner plate profile and Hyperglide+ technology as XTR. They’re designed to improve chain engagement and retention while working with the revised cassette ramps for smooth shifting under power. All chains are connected with a Shimano 12-speed Quick Link. The M8100 offers a more durable “chromized” surface treatment over the Sil-Tec coating on the M7100 chain.

Derailleurs and shifters

Just as was seen with XTR, the new XT and SLX derailleurs ditch the dogbone link that provided an option for a direct-mount hanger. Shimano claims the move back to an older design is due to creating clearance for the enormous 51T cassette cog. Both XT and SLX rear derailleurs feature adjustable clutch-mechanisms and bump stops for chain security and quiet operation in rough terrain. And the pulley wheels increase in size to 13T for smoother, quieter (and more efficient!) running.

The 2Way-release trigger shifters adapt the new ISpec-EV mounting system introduced with XTR M9100. This provides the shifter with sideways and rotational adjustment when mounted directly to the brake lever. Where XTR M9100 offers a claimed 60-degrees of rotational adjustment, XT and SLX are limited to 45-degrees. Regular banded clamp versions of the XT and SLX shifters are available too.

The XT M8100 shifters arguably offer the most obvious performance advantages over the cheaper SLX M7100. The XT right-hand shifter offers “Instant Release” for immediate shifting response at the derailleur, a multi-release for dumping down cassette gears, rubber padding on the levers, and an internal ball bearing construction for smoother lever operation. By comparison, the cheaper SLX M7100 version loses all those previously mentioned features, and can also only shift three gears (up the cassette) in a single lever press, whereas XT can do four.

Somewhat surprising is that Shimano has not trickled down its classy dropper seatpost remote from its XTR group.

Brakes, brakes, brakes

The XT and SL groups are available with the choice of either two-piston calipers for cross country, or four-piston brakes for trail/enduro riding. The new four piston brake calipers, which use a large brake pad, are said to provide 22% more stopping power.

By moving the clamping point and angling the lever, the new design is stiffer than before. Also pictured is the new XT four-piston brake caliper.

Both the XT and SLX two-piston calipers are carry-overs from the previous generations and retain a larger brake pad than what the two-piston XTR M9100 brake uses. The four piston calipers are closely matched to XTR, sharing the same updated D03S and D02S brake pads.

Looking to the levers, both XT and SLX now feature centrally placed bar clamps for a stiffer lever. Shimano’s power-increasing Servo Wave features in both XT and SLX, as does a tool-free reach-adjust dial. Where both XTR and XT levers offer a free stroke adjustment screw, the bite point on SLX is fixed. The option for a pared-back XC Race lever in XTR does not trickle down to XT or SLX.

Rotor choice is kept wide open, with Ice Tech Freeza rotors available only at XTR and XT levels, while SLX offers simpler Ice Tech options which retain the aluminium core for heat dissipation, but without the Freeza cooling fins.

Hubs and XT wheels

That new Micro Spline freehub design will surely reinvigorate demand for Shimano’s hubs and wheels, especially given Shimano’s new toothed freehub mechanism hides inside. That freehub mechanism sees a geared plate engage when pedalled, and is more similar to DT Swiss’ Star Ratchet design rather than Shimano’s pawl system. And while it’s close in concept, it’s not the same silent-running Scylence design initially announced with XTR M9100. That design was taken back to the drawing board.

Both the XT and SLX hubs are available in front widths of 100 and 110mm, and rear widths of 142, 148 and 157mm (a first for Shimano).

For now, Shimano will offer its 12-speed friendly wheels in XT only.

While XTR and SLX group levels only offer standalone hubs, XT adds complete wheel options, too. Available in both 27.5 and 29in options but only Boost-spaced hubs (110x12mm front, 148x12mm rear), the XT wheels are offered in two clear variants. Designed for cross country and trail riding, the XT M8100 wheels feature a 24mm internal width tubeless rim, laced with 28 double-butted straight-pull spokes front and rear. Wheelset weights for the 27.5 and 29in versions are claimed at 1,764 and 1,840g respectively.

The M8120 wheelsets are designed for more aggressive trail and enduro riding and feature 30mm internal width tubeless rims and 28 double-butted J-bend spokes. Wheelset weights for the 27.5 and 29in versions are claimed at 1,846 and 1,932g respectively.

Pedals

With the new component series comes updated SPD and flat pedals. Details are a little scarce, but it seems most of the changes are cosmetic. The exception will be the M8120 Trail SPD pedal, which will take on the longer and wider platform seen with the XTR M9120 pedals.

Component weights and prices

Many of the differences between XTR, XT and SLX can be explained with a set of scales. As Shimano’s flagship groupset, XTR is the lightest, and by a fair margin. In a common configuration, XTR M9100 is 365g and 513g lighter than XT M8100 and SLX M7100 groups respectively.

Quoted brake weights include 160mm rotor, centerlock locking, two caliper bolts and non-finned resin pads. * Includes RT70 rotor, ** Includes MT800 rotor, *** includes MT900 rotor.

Compared to XTR, the cranks and cassettes account for a fair whack of the weight difference. The XT M8100 cassettes feature the same 10 steel cogs as SLX M7100, but the two largest cogs are aluminium (10-51T) whereas only the biggest cog is aluminium on SLX. Similarly, the XT cassette offers more detailed machining of the spider.

All told, an XT group is approximately half the price of XTR, with SLX almost a third of what the flagship racing group sells for. Looking at groups based on four-piston brakes, a single 32T chainring, and 10-51T cassette (without rotors, hubs or pedals), expect to pay AU$2,899, AU$1,499 and AU$999 for XTR, XT and SLX respectively. US pricing is to be confirmed.

Based purely on weight, Shimano XT is best pitched against SRAM Eagle GX. Shimano SLX sits somewhere between Eagle GX and Eagle NX.

Still no Di2…

Shimano now has three new 12-speed mechanical groupsets, but nothing new on the electronic front. Previous generations of XTR and XT offered Di2 variants, and the robotic shifting makes a heap of sense where complicated suspension designs and constant muck are involved. Shimano admits that electronic versions are in the works, and it’s safe to assume they’ll share many of the same components as the mechanical counterparts, but that’s about all we know so far.

Similarly, Shimano is now the only major drivetrain manufacturer still using 11-speed for its flagship road groupsets. If XTR M9100 wasn’t already a giant glowing crystal ball of things to come, then the new XT and SLX groups should be viewed as big neon arrows of where things are likely headed.

Editors Picks