It’s hard to know where to begin with the new Shimano XTR M9100 groupset. Not least because it’s essentially three groupsets in one!

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Shimano XTR M9100 need to know

• New 12-speed drivetrain with wide range 10-51t cassette
• Dedicated 12-speed micro-spline freehub that’s blissfully silent.
• Hollowtech II chainsets with direct mount chain rings with the option to fit a double
• Twin and 4-pistion disc brake options with offset lever clamps
• New chain with easy to use split-link
• Price: see below

Shifters allow an easy thumb through the gears

With three rear derailleurs, three chainsets, three different cassettes offering 1×12, 2×12, and even a lightweight 1×11 option that sports a dedicated rear hub, it’s a lot to wrap your head around.

And that’s without even considering the direct mount double chain ring with three front derailleur options and the new push/push front shifter. With so much going on, it’s easy to understand why it’s taken Shimano so long to respond to SRAM’s 1x domination.

Shimano’s brakes are back to their best with twin-piston XTRs

And respond it did. With a new 12-speed 10-51t cassette Shimano has seen SRAM and raised it. At the XTR launch in Slovenia, where I had the chance to ride multiple bikes equipped with XTR on a variety of trails, Shimano was keen to point out that this wasn’t about one-upping SRAM’s 10-50t cassettes. It simply wanted to maintain even jumps between the top three top cogs on the cassette. And it’s paid off; the 51t cog acting less like a bailout gear and without the sudden change in cadence you maintain more momentum and traction on steep, loose climbs.

12-speed cassette tops out with a 51-tooth cog but it’s a pleasantly smooth progression to get there

To accommodate the 10t cog at the opposite end of the cassette, Shimano was left with no option other than to abandon its longstanding freehub design. The new Micro Spline freehub has a 7.6 degree engagement angle, and while not a rapid as some, it disengages completely while freewheeling to reduce rolling resistance and offer a blissfully silent ride. A less obvious advantage of the Scylence freehub technology is that it makes it really easy to determine if the rear brake pads are rubbing.

Rear mech loses direct mount but gains b-tension guide

Continuing with the reduced rolling resistance, Shimano is sticking with the bigger bearings that cup and cone hubs naturally afford. Traditionally these hubs have proved less reliable than the more common cartridge bearing designs, so it’s great to see that DT Swiss is already on board with a Micro Spline rear hub and we’re confident that other brands will follow suit.

Rear hub features new Micro Spline body

Being second affords hindsight that wasn’t privy to SRAM when it first developed XX1. As such, the new XTR rear derailleurs get gradients on the back of the cage to make set-up easier and tool free. To decrease chain tension in the lower gears and better accommodate the 51t cog, Shimano has also switched back to a more traditional rear derailleur layout, so it’s nothing like as low profile as the old Shadow Plus design. Direct mount is also gone, but the new XTR rear derailleurs retain the chain stabilizing Plus clutch, which can be adjusted to optimise chain tension. And thanks to softer plastic that affords some flex in the upper jockey wheel, shifting under load is smoother and much quieter that previous Shimano drivetrains.

Drivetrain weights Shimano XTR Vs SRAM XX1 Eagle

Cassette: 370g Vs 367g
Rear derailleur: 244g Vs 268g
Shifter: 122g Vs 123g
Chainset: 531g Vs 468g
Chain: 244g Vs 225g

Totals: 1511g Vs 1451g

Space-saving clamp stiffened by offset nub

The latest r-hand XTR shifter retains Shimano’s multi-release feature that lets you down shift two gears at a time, great when dropping into steeper trails where the bike is instantly up to speed. On previous Shimano shifters the multi-release feature always felt clunky in use, more like an accidental hack than an actual design feature. With the new design the double downshift is much slicker than before, with a noticeably lighter shift action needed to activate the second shift – combined with the new Hyperglide + cassette dumping gears is an absolute breeze.

The new multi-faceted groupset covers everything from enduro to XC

The shifter levers have been repositioned too, making it much easier to down shift with your thumb and when you factor in the increased rage of adjustment on the latest I-SPEC mount, it is way easier to obtain an optimum shifter position without compromising your brake lever setup.

We’ve always been big fans of Shimano’s Hollowtech II chainsets and I for one will be mourning the loss of the twin-bolt design that secured the left crank arm; it was simply bombproof. Sure, the new one-key release looks much cleaner, and retains the option to preload the bottom bracket bearings, albeit with an integrated collar, but the shorter axle splines that connect the spindle with the L-hand crank arm are reminiscent of older M970 Shimano XTR chainset that was much less robust.

Direct-mount chainset is a welcome step forward

The biggest change to the chainset though is that it no longer has an integrated spider. Instead, it now uses a direct mount for one-piece chain rings from 30 – 38t in two tooth increments. It’s a positive move and one that doesn’t punish riders wanting the increased gear range of a double chainset as you can still fit a one-piece direct mount 38/22t double. For big mountain 29er riders looking for a 28t chainring, Shimano isn’t currently offering one, so that could be one area where aftermarket chainring manufacturers could step in.

It’s no secret that Shimano’s recent crop of brakes had issues with the bite point changing. Well, after three days of riding the new four-piston and lightweight twin-piston XTR brakes that issue appears to be a thing of the past.

>>> How to bleed Shimano mountain bike disc brakes

That said, with Shimano’s dedicated left and right hand brake levers, it’s still imperative to bleed the brakes if you swap the hoses around, as they are still sensitive to air ingress. The new servo-wave design of the lever on the 4-piston brake is seamless in its transition from increased pad movement to extra power, so modulation is first rate. The offset lever clamp combined with the nub on the master cylinder is also a great feature as it increases the effective clamp width for improved stiffness without eating into available handlebar space for additional controls like Shimano’s new under-bar I-Spec dropper remote.

So the shifting is slicker than ever before, the gear range is impressive and 2x traditionalists and weight weenies haven’t been left out in the cold. The new multi-faceted Shimano XTR groupset covers everything from XC to enduro, while giving riders the ability to mix and match aspects of the groupset for there specific needs without any obvious compromises.

Shimano XTR M9100 pricing

• Rear shifter £95
• Rear mech £190
• Crankset £310
• Chainring £100
• Chain £50
• Front hub £135
• Rear hub £250
• Cassette £290
• M9100 Race two-piston brake £209
• M9120 four-piston brake £219