Shimano Dura-Ace ST-R9120 STI Levers
Dura-Ace 9100 is the second generation 11-speed version, but the first with a true complete Dura-Ace hydraulic braking system. The ST-R9120 STI Levers feature all of the shift upgrades found in the mechanical R9100 STI Levers, but are built with the new hydraulic disc brake system. Now you can get high performance road hydraulic disc braking with the standout cable actuated shifting that defines Dura-Ace mechanical.
The ST-9120 STI Levers actually manifest some important changes that may seem incremental to some folks, but required considerable overhaul of the internals. The end result: backwards compatible 11-speed shifting and braking controls that reduce lever throw and effort for faster more efficient shifts, greater brake lever reach adjustability, advanced ergonomics, and a new standard for performance. There are three set of cyclists who will be looking at these R9120 STI hydraulic disc brake levers. The first is self explanatory: you are building a full Dura-Ace 9100 drivetrain with Dura-Ace or BR805 hydraulic disc brakes. The second is you are currently running Shimano road hydraulic disc and want to update your RS685 11-speed STI lever set to the R9120. The third is the cyclist who has 11-speed STI 9000, 6800 or 5800 levers and is swapping over to disc brakes on a different frame and wants to go right to Dura-Ace. Sold here as Front and Rear options, the R9120's come with a complete BR-R9170 hydraulic flat mount caliper and full hydraulic hose set.
Start with the shifter body ergonomics. All rides begin when you place your hands on the lever. The body feels much less bulky than the RS685 and the lever top/hood set-up naturally on contemporary handlebars if a flat, wrist-friendly profile if desired. You will immediately recognize and feel that Shimano has moved to a textured hood for the first time. The rubber material Shimano uses has long been effective in wet or dry conditions, but as it wears, it can get a bit slick. The material used is new, and the overall effect is that the hood feels more natural in the hand, with better grip. Dura-Ace 9000 series levers offered 10mm of reach adjust for the brake lever. With 910 you now get 14mm, and Shimano pre-sets this at the 10mm mark, so if you large hands or long fingers, you can move the lever out 4mm, a substantial difference. Of course those with smaller hands can also take advantage and shorten the reach by 10mm. The final ergonomic refinement comes in the form of a larger surface for the paddle on the secondary, or release lever. This simply makes the paddle easier to find, especially when in the drops, and offers more room for errors, especially with gloved hands.
The most important change has come with the length of the lever throw and shift actuation itself. Shimano's mantra for 9100 has been "Optimal Input-Maximum Output", and though it applies throughout the groupset, it is most obvious in the shift levers. The throw and actuation of the main (outer) lever has been reduced by 24%, and the throw of the release (inner) lever by 14%. The action feels more precise and requires less effort and reach resulting quicker, more responsive shift action. Taking a cue from the XTR mountain shifter, the inner lever now delivers Instant Release, with no hesitation from the lever in engaging the shift. Previously there was what could be called a dead spot, which was intentional. Now that is gone and the results are both obvious and welcome when dropping a gear.
Mechanical shifting is hugely impacted by friction within the cable and housing system. The OT-SP41 Polymer-Coated Derailleur Cable Housing has lightweight silicone grease inside the lining and sealed end caps to allow the cable to glide smoothly and remain free from contaminants. The cables themselves are high-grade SUS stainless steel, which is highly anti-corrosive, exceptionally strong and lightweight. Shimano coats the cable with a polymer treatment to prevent the cable from taking in any grime or even grease that can impact its performance. With the coated cable gliding through the flexible, greased housing, the overall reduction in friction, even with tight bends, is impressive and clearly noticeable.
In engineering hydraulic the braking system new BR-R9170 flat mount brake calipers, Shimano wanted to drop weight, increase power, reduce heat build-up and offer more modulated feel through the system to the lever. Each caliper is just over 250 grams, and very low profile. The lever features free-stroke adjustability for controlled throw and pad contact point. The mono-body caliper is made from aluminum, and has an anodized finish. A ceramic piston drives the caliper action through the pads. Shimano uses a mineral oil based fluid system, which is stable and safe to use, with a straightforward one-way bleeding via their funnel and fluid process. Shimano has continued their relationship with IceTech for optimal cooling at the rotor/pad/caliper interface. The excellent L02 finned resin pads are included here. The pads provide the quietest, most consistent stopping power and modulation, while the aluminum fins serve to quickly release heat off the pad backer, which is combination of steel and aluminum. You get the pad stiffness and reliability for optimal power, without fade or power loss from overheating.
The flat mount standard is becoming ubiquitous on road disc, and many cross disc, frames and forks. Flat mount calipers can also be adapted to post mount systems. The caliper system has a minimal aero footprint, and there is next to zero energy loss from the mounting system, which has allowed frame, fork, and calipers to be stronger and lighter than ever before, with increased performance. Rotors do not come with this kit, but the SM-RT900's are newly designed with IceTech, and are available in 140mm and 160mm sizes for Center Lock disc hub use.
Of course,given the ST-R9120 STI Levers being Dura-Ace, the components, hardware, and finish are top-notch. The main body is CFRP composite, which is lightweight, exceptionally strong, and utterly reliable. The lever blades are carbon fiber, and the mechanical systems ride on 4 super smooth bearings. Shimano only uses their most reliable materials in Dual Control shifters, which is why longevity, durability, and supremely consistent performance are not only expected, but realized. Now you can take full advantage of true road disc specific braking without compromise, while maintaining your preference for Details