Shimano's hydraulic disc brake systems are generally considered the best overall options in the MTB market. From performance to reliability, to ease of service and effective design with good power and modulation, nothing else hits all those marks. While feel, power and performance are certainly subjective, the service and reliability aspects are easily confirmed. Still, Shimano constantly seeks to improve, and after adding a mid-line 4-piston XT-level brake, we now have a an 4-piston XTR BR-M9120 brake as the pure trail-oriented model at the top level, a major upgrade of the 9020 2-piston model. As such Shimano has improved braking power at the caliper by a full 10%, without sacrificing feel or modulation. The 9020's were pretty powerful but could fade under long, hard descents. Early reports on the M9120's indicate this problem has been addressed.

While the mono-body aluminum 4-piston, IceTech fin compatible caliper has been grabbing all the attention, looking past the impressive qualities of the M9120 disc brake lever would be a major mistake. To the tool-free reach adjust, aluminum master cylinder, and power inducing ServoWave pivot technology, add in a new lever shape, the I-Spec Evo mount compatibility and overall quicker lever to pad engagement in free stroke. M9120 isn't built tougher to reassure you, but the build quality designed for the rigors of heavy trail and Enduro riding is comforting nonetheless. An SUS stainless bolt secures the mount. The lever is anodized aluminum. As a full assembly with 160mm rotor (not included), the M9120 system weighs about 70 grams more (approx 385) than the M9100 XC version.

The lever features funnel bleeding, as you'd expect, but the Shimano mineral oil based 4-piston system is NOT a one way bleed system, so check the tech specs before attempting. As stated the caliper is also built to accept IceTech finned brake pads and these units are coming through with the N04C Metal pad (w/ IceTech radiator fin). Shimano does offer a resin version, but we generally feel those should be used for events, and preferably in dry-ish conditions. The power of the M9120 assembly can easily destroy resin pads in short time. As opposed to the M9100 version the M9120 also features a caliper end banjo assembly with the SH-BH90-SBM hydraulic hose kit. The lever end still features a straight connection. For both the M9100 and M9120 disc brake systems, Shimano recommends their new RT-MT900 disc rotor, which was developed with IceTech for greater cooling efficiency and has a new Freeza design with heat defeating paint.

Overall we expect the XTR BR-M9120 Disc Brake to suit more riders than the lighter weight M9100 version. The ServoWave lever and 4-piston caliper combine for the best power Shimano has ever produced outside a Saint grade brake system, with improved overall feel and top notch performance with IceTch finned pads and the (not included) RT-MT900 Icetech Freeza rotor. Any trail rider will be able to feel the power and control, and won't be thinking about gram counting.