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Shimano’s Shadow Plus XTR rear derailleur has been the biggest product revelation I’ve experienced in 2011 and truly makes riding better. Shimano took its XTR Shadow rear derailleur and added a one-way friction clutch that only engages when the derailleur’s cage moves forward, which typically (and frequently) happens when the bike rolls over rough terrain. The device practically eliminates slap and, because it keeps the chain under tension, it also limits the chance of a chain dropping off the chainrings.
A gold-anodized “stabilizer switch” turns the clutch off to ease wheel removal and installation. And all it takes is riding with that switch off to realize just how effective the Shadow Plus is on the trail. The new derailleur is so quite that other noise—the whirring of a chain or the crunching of dirt under tires—suddenly become noticeable. Not only is clatter reduced, but I’ve experienced exactly one dropped chain since installing the Shadow Plus three months ago. That’s astounding: Normally, if I am not using a chainguide, I would drop my chain about once a ride.
The derailleur is adjustable too. Under the cover hides a small wrench that tightens or loosens the friction band, which is connected to the P-knuckle. After a couple of months of riding I felt compelled to snug the tension band’s adjustment bolt–there seems to be a break-in period after which the tension stabilizes. All the pieces of the Shadow Plus mechanism are replaceable if worn out. Shimano, however, says it has yet to sell any because the derailleurs have not been in the field long enough to break. Time will tell how long these derailleurs will withstand repeated abuse, but so far nothing indicates they won’t survive as well as traditional XTR models.
There are a few tradeoffs, however. Shifting, for one, feels heavier at the lever—gone is Shimano’s acclaimed light-action feel. This only occurs when moving up the cassette using the large thumb paddle—shifting down the cassette still feels light and easy. The tighter the bolt is on the friction band, the heavier the shift-feel. I tightened the bolt until the shift felt too heavy and then backed it off a touch. Shimano’s torque specification for the adjustment bolt ranges from 3.5 to 5.4 Nm (30 to 47 in. lbs.). I seemed to like it right around 4.5 to 5 Nm.
I’ve heard some riders claim that the derailleur can affect suspension performance, especially on bikes with extreme chain growth. While the theory is plausible, I’ve never felt it.
The Shadow Plus is also heavier than the traditional version, but not by much. While a standard XTR model weighs 176 grams, the Plus tips the scales at 208 grams. Even top XC racers, however, believe the small weight penalty is nothing compared to the potential gains, especially since it practically eliminates dropped chains. At the U.S. National Championships earlier this year, Adam Craig even borrowed the Shadow Plus off his Super-D bike to use during the short-track race. Shimano has said that part orders for next year’s team bikes indicate that many more XC riders will be rocking the Shadow Plus in 2012. That reminds me—it works just as well on hardtails as it does on full suspension models.
The only other downside is the product’s cost. The clutch-equipped Shadow Plus is currently only available on the XTR derailleur, which costs $250. Shimano has not confirmed that the technology will trickle down to more affordable product lines, like the XT or SLX, but given the advantages, it seems inevitable, especially since SRAM is rumored to be working on a similar version.
Despite the cost, and the small weight penalty, the XTR Shadow Plus is, in my view, the greatest innovation of 2011. Like other innovative products—suspension forks, clipless pedals and dropper posts—there’s no going back once you try it.