I have one KHS sixfifty 500, I want to upgrade my bike so I have already bought

Shimano Deore XT M771 front derailleur Shimano Deore M590 shifter

So I want to know your suggestion to rear derailleur and cassette?

I want to know if exist rear derailleur with lock.

I was planing to buy Shimano Deore XT M772 rear derailleur but its hard to find in Brazil, so has a model like this?


  • I've never heard of a locking mechanism in a derailleur. Would be pretty useless because the bike isn't fastened to anything.... it would be worse those dutch horseshoe-shaped Axa locks because the bike would still roll normally, just not pedal.
    – Criggie
    Commented Apr 20, 2016 at 12:56
  • 1
    The lock button dont let the chain scratch the frame Commented Apr 20, 2016 at 13:10
  • 3
    Maybe you're talking about Shimano Shadow Plus?
    – Batman
    Commented Apr 20, 2016 at 14:52
  • Yes, I looked at Google and you are ok. Commented Apr 20, 2016 at 18:22
  • 1
    Personally I find the SLX range to be of pretty high quality / performance / durability. With XT and XTR you're mostly just paying more for the reduced weight benefits
    – Bucky
    Commented Apr 23, 2016 at 14:20

2 Answers 2


Indeed as per the comments the 'lock' mechanism on Shimano rear derailleurs (to reduce chain slap) is called "Shadow Plus". Whilst this was initially a feature of the higher end models (XT / XTR) a few years ago, it has since filtered down to some lower models, such as SLX and Zee (although I think not yet on Deore ... anyone correct me?!)


Since seems you got a 9 speed shifter, you are going to need a 9 speed cassette, like the Shimano HG80 SLX 9 Speed Cassette.

As for deraileurs, you can use the Shimano RD-M615, which is marketed as 10 speed, but it will work with your setup with no problem (I used an Alivio RD which is 9 speed on a 7 speed bike for a long time, it gave me very nice shifting and reduced chain slap on that bike, which I used to go to work.) What is important to match is the shifter and the cassette, they must be of the same speed.

As for RDs, you can use practically any shadow plus RD you can get your hands on as long as its medium or even long cage. Because you are on 9 speed, the medium cage is enough for you, will give you a lighter RD with better ground clearance, but a long cage one will do the job too.

The ones you cannot use are the Zee and Saint RDs, because they are short cage model, so if you are going for double or triple rings in front, they cannot take up enough chain links for the front shifts.

  • 10speed mtb derailleurs use different ratios to 9speed so not sure how well this will work, likely not ideal
    – Swifty
    Commented Aug 1, 2018 at 7:01

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