Shimano launched its seventh new XTR groupset last year, and earlier this year followed that up with the announcement of an all-new Shadow Plus rear derailleur that promised to eliminate chain issues.
RD-M985, to give it its official name, features a clutch stabiliser system inside the pulley cage which increases the spring tension. When the lever is pushed into the ‘on’ position, a ratchet gear virtually locks the lower pulley cage into position, only allowing a small range of movement for chain growth.
To get the wheel out when loading your bike into the car, the lever pushed into the ‘off’ position disengages the clutch and allows the mech to swing forward. It’s an easy-to-use design that makes a big difference over the standard rear mech. We only need to look at the white chainstays on our test bike that carry the scars of chain slap with a standard XTR mech to see what difference this could potentially make.
And it really works. Chain slap, the sound of the chain hitting the chainstays over rough ground, is completely eliminated. Not only is riding thus a quieter experience, which has to be good enough reason alone to recommend it, we also experienced a lot less chain droppage, handy if, like us, you’re not running some sort of chain device.
We’re still running a standard Shimano XTR rear derailleur on another test bike, and the shift performance is identical, with crisp and precise changes up and down the cassette. Upon initial testing we did notice a slight heavier feel at the shift lever, but it’s almost indiscernible after a few miles of riding.
Everything else remains the same on the Shadow Plus mech. It’s Dyna-Sys 10-speed with the same low profile design that does well to avoid rock impacts. Improved cable routing is a boon and the full carbon fibre outer pulley not only looks snazzy but reduces weight, and the cable pull ratio has been made for more accurate shifting with a more linear feel.
Compared to the standard XTR RD-M980 Shadow mech which costs £149.99, you’re paying an extra £20 for the XTR RD-M985, which seems a small price to pay for the vastly improved chain management the design offers.
It’s more expensive, but most trail riders will appreciate the improved performance and lack of annoying chain slap in Shimano’s latest XTR rear mech.