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Electronic shifting is coming to mountain bikes, and it might just alter the way we think about changing gears forever.
Shimano XTR 9050 Di2, announced formally on Friday after more than a year of speculation and leaks, has the option of functioning similarly (ok, identically) to a system hacked by the tinkerers at Fairwheel Bikes for Interbike two years ago, with both derailleurs controlled by a single shifter. It can be used with just two buttons, up and down. Pushing those buttons move the chain through a sequential series of gears, shifting both the front and rear derailleurs.
That’s right, no more front shifter, even for the available double and triple cranksets. The system will automatically shift the front and rear derailleurs simultaneously to give you the next sequential gear. Just tell it up or down, and it does the thinking for you.
Shimano calls it Synchronized Shift, and it’s the boldest move we’ve seen out of the company in years.
The new group will be based around Shimano’s top-tier XTR mountain components, swapping out the deraillerus and shifters for battery-powered models. Like mechanical XTR, it will be available in both Trail and Race versions, and in multiple drivetrain configurations, including single, double, and triple cranksets.
Availability is set for late 2014, and prices have not yet been set, though Shimano says the price difference will be similar to the difference between Dura-Ace mechanical and Di2 groups.
Read on for details and check out Lennard Zinn’s first ride impressions of the bold new group.
XTR Firebolt sequential shifter
At the heart of the new 9050 group is the XTR Firebolt shifter, which Shimano says is designed “entirely by human ergonomics, not by the needs of a mechanical mechanism.” It’s a rotary shifter, with two independently-adjustable paddles rotating around the bar.
Stroke is very short, with a decisive click, but of course shift effort has been decreased even relative to the most buttery mechanical system. The top paddle shifts up, and the lower paddle shifts down, just as you’d expect.
A front shifter is available, and the whole system can be set into “manual mode,” allowing it to function just like a normal drivetrain. But Synchronized Shift is designed to be used with just a single shifter. The system will decide when to shift the front derailleur, moving across the drivetrains’ entire range. The point at which it shifts the front derailleur will change depending on whether the system is being upshifted or downshifted, and can be manually set as well.
Because the shifter is electronic, it’s also customizable. Two different pres-set shift maps and one custom map are available, to be selected based on terrain and personal preference. For those concerned with surprise front shifts, the system sends out an audible alarm before a front shift.
Settings can be adjusted by connecting the battery charger for an internal Di2 battery to a personal computer with Shimano’s software. For diagnostics, Shimano recommends heading to your local dealer.
The shifter, as well as its associated digital status display (more on that later), is compatible with Fox’s electronic suspension components as well.
XTR M9050 Di2 rear derailleur
The XTR Di2 derailleur borrows much of its shape and technology from the mechanical systems, including the Shadow+ mount, which tucks the derailleur closer to the frame to help prevent damage, and roller clutch, which increases chain control and decreases chain slap noise.
The derailleur connects to the rest of the system via Shimano’s E-tube wires, and is available in both medium and long cage versions.
As Lennard Zinn points out, one advantage of the Synchronized Shift system is the ability to run a short cage derailleur and shorter chain on both 2x and 3x drivetrains. The system can simply be programed to avoid those large-large gear combinations that would normally be impossible with a short cage derailleur.
Like the road Di2 derailleurs, XTR Di2 will have a “saver mode,” automatically triggered in the event of a crash to keep the system from hurting itself. Bumps and crashes are much more frequent in mountain biking, but presumably Shimano has set the threshold for triggering saver mode somewhat higher than it has on its road derailleurs. Regardless, it can be turned off by holding the button on the Di2 controller for 3 seconds.
XTR M9050 Di2 front derailleur
Front shifting has always been Di2’s claim to fame, the area in which it truly set itself apart from every other drivetrain system on the market. The dependability and precision of the system is what makes Synchronized Shift possible — the front shifting simply has to work perfectly every single time or the entire system will never win over riders.
The XTR Di2 front derailleur is a claimed 25% more powerful than the XTR 9000 front derailleur, providing reliable gear changes even under load. It auto-trims, just like its road brethren, as the chain is shifted across the cassette. And, when the chain reaches a certain point on the cassette, it will automatically jump to the next chainring.
The mount system, while not particularly sexy, is fantastic. The same derailleur body is used regardless of the frame requirements or the number of chainrings used, with different mounts available for the various frame mounts.
Di2 Display Unit
XTR Di2 will come with a handlebar mounted display unit, creatively dubbed SC-M9050 Display Unit, that can be used for monitoring Di2 data. Gear selection, battery level, and shift mode are all a button push away.
It is the display unit that will beep at your as you approach a front shift, and it allows for easy swaps between the two pre-programed shift maps and a manual map. It also provides a charging port for the system and allows for derailleur adjustments, just as the current free-floating Di2 box does.
The Display Unit is also compatible with Fox’s electronic suspension systems, and will display whether a fork or rear shock is in Climb or Descend mode.
When run without the optional front shifter, total weight of the XTR Di2 is nearly identical to that of the mechanical group. Of note, too, is that wires are lighter than cables by about 60 grams, variable depending on housing length.
Here’s the breakdown, all claimed weights:
XTR Di2 front derailleur: 115 grams (Di2 is 5 grams lighter than mechanical)
XTR Di2 rear derailleur: 289 grams (Di2 is 68 grams heavier than mechanical)
Display Unit: 30 grams
Shifter: 64 grams (Di2 is 36 grams lighter, 136g lighter if only one shifter is used)
Lennard Zinn has ridden the new group, his first-ride thoughts can be found here.