Shimano ZEE RD-M640 Shadow Plus Rear Derailleur

It's ZEE best derailleur around.

Chain slap is something we all have to live with, but Shimano's ZEE RD-M640 Shadow Plus makes it a whole lot less cringe-inducing by including its now-famous clutch technology. By increasing spring tension when it's engaged, the clutch reduces slap and the risk of dropping a chain, making it a killer choice for riders who spend decent chunks of their time pounding through rock gardens and over rugged trails. When the clutch is off, the reduced tension makes it easy to pop the derailleur out of the way for wheel removal. It's made of aluminum and steel, so it's durable enough to be knocked around with no ill effects, and comes in both a DH and Freeride model, so you can dial it in for the type of riding you do most often.

  • Aluminum and steel construction
  • 10 speed
  • Short cage
  • DH (28-tooth max) and Freeride (36-tooth max) versions available
  • Reviews
  • Q & A

Great for 1x drivetrain

  • Familiarity: I've put it through the wringer

I decided to try this out and see if it would work with 2x setup; the short answer is no. The short cage doesn't have enough chain uptake to be able to use the smaller cogs on the rear cassette. Stick with at least a medium cage XT if you're wanting 2x. Oh well, it finally pushed me into a 1x setup.

The 10-36 (FR) works perfectly with that range. It appears to have the range to push it up to a 40T cog on the rear if you go with a large cog conversion. I haven't tried that yet. The clutch is easy to adjust. Solid chain tension and crisp, quick shifts everytime!

Does the job well

  • Familiarity: I've put it through the wringer

No frills here, typical Shimano excellence. Have it on the DH and its been keeping be cranking for about a year. Will buy again when I have the inevitable Derailleur smash this season.

Shifts great and and cheaper vs saint!

    Bent my Saint short cage, bought this and it shifts just as well. Great to save some money! Installed with no issues.

    Great for a DH rig

    • Familiarity: I've used it several times

    After a few rides I'm pretty impressed with this thing. Shifts smooth, zero chain slap and I love the fact that there's a clutch. You can't beat the price either.

    Shimano > *

    • Familiarity: I've put it through the wringer

    This derailleur rocks. I've got the medium cage on my 1x10 hardtail and with the clutch I don't need a guide. Chain slap is a thing of the past with the Shadow awesomeness.

    ZEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!

      Purchased this ZEE derailleur to convert my wife's Myka FSR from a 2x9 to a 1X10. For the inexpensive price this derailleur works great. She's had no issues since I put this on a few months back.

      What goes up must come down.

      It got me to the top of City Creek Trail in St. George, UT without any problems. Always works like it should and the short cage is great for coming down.

      What goes up must come down.

      What more do you need?

      This is the Zee derailleur setup on my 2015 Giant Trance 2, very easy to install, shifts great and keeps the chain on.

      What more do you need?

      Zee for Dayz!

      • Familiarity: I've put it through the wringer

      I put the Zee paired up with a RaceFace Narrow wide ring up front and I have never had any issues with the chain falling off. The clutch system works just like it should, keeps the chain nice and tight and the short cage really keeps down the rattle while bombing those tight single track runs. Shifting is smooth and has a great look to it. Very impressed with the Zee system.

      Great Product

      • Familiarity: I've put it through the wringer

      Good looks, decent weight, solidly built. Clutch works as intended, this paired with a narrow wide ring has been excellent, no dropped chains. Shifts are crisp

      Impressive Unit

      • Familiarity: I've put it through the wringer

      I've got this derailleur mated with ZEE cranks and 1x10 speed XT gearing. With a Narrow Wide ring upfront no chain guide and the clutch engaged I have had no issues with the chain derailing and the shifting is smooth as silk. Before installing the NW ring I did have a few issues with the bike spitting the chain, but once I upgraded there were zero issues. So far so good with the ZEE!