Project 24.2 Review: Shimano RD-M985 XTR Shadow Plus rear derailleur

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First introduced just about a year ago, Shimano’s XTR Shadow Plus rear derailleur represents one of the first major advances in rear derailleurs that the mountain bike market has embraced in a very long time.  Starting with their low-profile XTR rear mech, Shimano have added (Plus!) a one-way friction clutch to the cage pivot.  By making the derailleur much more willing to take up chain slack than give it, the chain slap is reduced.  Less chain slap means less noise, less frame damage, and (most importantly) reduces the likelihood of the chain being dropped.  After extensive XC and trail use and on the eve of the release of SLX and XT versions, has the added complexity and 30g been worth carrying?  Hit the jump to find out!

First mounted on our Project 24.2 race bike, the long-cage Shadow Plus rear derailleur has been on two very different bikes and ridden in countless settings.  The unidirectional carbon fiber cage is subtly sexy while the rest of the derailleur makes use of Shimano’s extensive aluminum forging experience.  In my opinion, Shimano have managed a nice balance between organic and machine aesthetics with their latest flagship group.

Because the clutch makes the cage extremely reluctant to rotate counter-clockwise, Shimano have added a small switch that disengages the “Plus,” allowing for quick normal wheel removal.  The gold switch and bulky pivot are the only indications that anything unusual is going on inside- installation and adjustment are easy for anyone who’s installed other rear derailleurs.

Paired with 10s XT shifters and XT and XTR cassettes, the Shadow Plus shifts very well.  Current groups don’t shift with the silkiness that was once Shimano’s trademark- but that’s a response to the market rather than a failure on their part and shifts are better defined as a result.  With the Plus disengaged, shifting is ever-so-slightly smoother, but for me the system’s benefits outweigh slightly clunky shifting.

And the benefits are clear.  The only dropped chain I’ve suffered in the past six months was when the bike slammed into a rut- and the gold lever was disengaged.  More satisfying is the way in which the Shadow Plus keeps my bikes quiet.  Appealing to both sides of my personality, reduced chain noise makes coming up on hikers much more civil while increasing the psychological impact of race course passes.  As a bonus, the derailleur should  reduce chain-inflicted damage on carbon chainstays.  Win, win, and… win.

Under a small cover, the Plus clutch is adjustable using the elfin wrench stored there.  Seeing as I like smooth cables and was one of four people who embraced Shimano’s velvety <del>Rapid Rise</del> Low Normal system, I actually backed the clutch off 1/4 turn (1/2 turn was too much), which improved shifting while maintaining the system’s benefits on all but the roughest trails.  After having had six months to adjust, the only time that shifting feels balky is after riding an older XTR-equipped bike.  The rest of the time, it feels just fine- fresh cables and housing make much more of a difference to lever feel than the Plus system.

The best that Shimano can do has never come cheap (or, to be fair, cheaply made).  In keeping with this precedent, Shimano is asking $250 for the RD-M985 XTR Shadow Plus rear derailleur.  That’s a lot of dosh for the most exposed part of a mountain bike- but this summer’s SLX and XT Shadow Plus releases will be considerably more accessible.  My sample does exhibit a surprising amount of lateral play when wiggled side-to-side in the stand.  It doesn’t seem to impact performance- but Shimano have proved that they can do better.

Is it worth it?  A reasonably careful rider, I still have 2-generation old XTR derailleurs in my personal fleet.  The anodizing has faded from pewter to silver, but I can’t see replacing something that still works as well as they do.  XTR gear may be pricey, but it does last.  While I can’t recommend throwing a perfectly good mech on the shelf, on a new build or when a stick eats your XTR rear derailleur a Shadow Plus replacement should be a no-brainer.  The added weight is negligible and even the weight-weeniest racers can benefit from fewer dropped chains.  The benefits are clear and the word is out- I simply don’t see any reason to run non-Plus derailleurs on the trail once the XT and SLX models hit.

marc

bike.shimano.com

Comments

jdog - 06/07/12 - 8:37am

This is by far the most impressive innovation in bicycle drivetrains in years. It only takes one, near silent ride to become a believer. This marks Shimano’s triumphant return to the top shelf in mt bike components. These will shortly ship in XT and SLX quality. This is one of the few upgrades that you NEED!

Marcassin - 06/07/12 - 9:19am

Can’t wait to buy an XT shadow plus this summer. Since I’ve broke some derailleurs in the past while crashing, I guess I’m not the only one, I’ll have to wait for the XT, the cheaper the better ^^

Mack from Texas - 06/07/12 - 10:19am

I hae been riding one of these since the spring. Came on my Niner RDO, and it is awesome!

satisFACTORYrider - 06/07/12 - 10:31am

i have a feeling the on/off option will go away and have a constant tension that might be dealt with thru the shifter mechanics. it works so well on I can’t think of why i would ever have the clutch off. looking forward to run a slx/zee mix.

yeah right - 06/07/12 - 12:16pm

hmm.. satisfactoryrider… your “feelings” deceive you. I don’t see how it would be at all possible to handle the clutch switch through the shifter. The two mechanisms of shifting and engaging the clutch are completely separate from each other and would require to separate cables and another lever, which is just lame.

Furthermore,the purpose for disengaging the clutch is simply to remove the rear wheel and/or perform maintenance and adjustments. There would never be any reason to disengage it on-the-fly.

Brian - 06/07/12 - 1:44pm

Have been running the + derailleur since it’s first available date as a 1×10 with no chain guide and have only dropped my chain once, backpedaling through a very rooty section on a trail. No big deal. Very much worth the money.

Juan Pablo - 06/07/12 - 5:53pm

Best improvement to my drivetrain. Excellent.

I do have an issue with the shifter clamp bolt … and it had an issue with my patellar ligament … bad injury .. this thing went right into it … Shimano should know better than to place the sharp edge of the bolt facing that dreaded painful spot …

The ‘knee-facing’ surfaces of a handlebar clamp should be SMOOTH.

Kovas - 06/08/12 - 12:00am

Is the Shadow-plus backwards still compatible with 9-speed xtr? Or does it require a full 10spd upgrade? I guess my question is – is the pulley cage too narrow to run a 9spd chain?

Marcassin - 06/08/12 - 4:24am

@Kovas

The pull ratio is different between 9 and 10sp. So the answer is no :(.

Robert - 06/08/12 - 2:30pm

I’ve been running the shadow plus since October. Bought an XTR bike just for the brakes. Didn’t like the shadow + at first. Until I figured out how to adjust the tension — the upshifts were not XTR-worthy with the lever on and I would drop the chain constantly with the lever turned off. Then I figured out how to adjust the tension on the cam, now it is fantastic! No chain suck, dropped chains, or chainstay slap.

Christian - 06/08/12 - 5:34pm

I wish they had done SL-M985 with a fix for the shifting cable getting stuck below instead of on the drum where it is supposed to roll up. XTR in general is definitely still very good and I find the RD-M985 quite impressive, but the current shifters SL-M980 are definitely a lot more ugly and a lot less functional than the SL-M970s.

Tony - 06/09/12 - 9:32am

It would be nice if the SLX or XT have a version for 9 Speed bikes, that’s all I need: XT, 9-Speed and short cage. 10 Speeds are nice, but I don’t like to be forced to update everything.

mountguitars - 06/09/12 - 3:29pm

for those who don’t know why there’s an on/off switch, watch this video: http://www.youtube.com/watch?v=R9eHUWFCObg

Tom - 07/23/12 - 6:25pm

Could someone explain what is the pull ration? I don’t understand why this 10 speed deralleur is not backwards compatible to a 9 speed drive train. In fact a 9 speed shifter will pull a shorter range compared to 10 speed. And the detents are in the shifter, so where is the problem with compatibility?

Marc - 07/23/12 - 8:26pm

Tom,

It’s a combination of the two. The shifter dictates how much cable is pulled for a given ‘click’ and the derailleur’s geometry determines how far a given amount of cable pull moves the jockey wheels across the cassette. Shimano prioritized the new groups’ performance over backward compatibility, so there’s no mixing and matching…

marc

matt h - 08/25/12 - 11:30am

I just tried to fit a Zee rear mech, with a 9speed shifter and sprockets, it doesn’t work!
If you want a cluch rear mech, you’ll need to upgrade EVERYTHING to 10sp (in front mech)

Hutch - 12/06/12 - 4:28pm

Just to 1+ Matt and others, A Zee derailleur does not work with an XT shifter in the experiment I’ve just done (damn… just bought the shifter too…)

Trail - 09/12/13 - 3:08am

Im guessing that the posters so far have by now seen the comments and mods that have been made to make the 10s RD work on 9s systems?
Ide like to hear from anyone that has been able to make a X0 sram RD work with a 10s shimano shifter. Thanks

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