Is my Shimano Deore SLX dérailleur a medium or long cage? I have a Scott E-Genius 730 Plus and would like to replace the rear dérailleur (the probable cause of difficulties described in my last question). It's a Shimano Deore SLX Dyna-sys unit, it's for a 10-speed cassette, and has a code RD-M7000 stamped into a metal part of the body. The drive system does not have a front dérailleur.



I have found a Shimano Deore M6000 Shadow+ 10 Speed Rear Mech, which I assume would fit. It asks me whether I want a medium or long cage, and I don't know.

I was hoping I could find a Bill Of Materials ("BOM") for my bike, perhaps by looking it up on the Scott website by its frame number, or scouring through the supplied CD-ROM and manuals. None of these have provided much information, other than basic brand information that I already know. I have also looked at the Shimano website, but this does not seem to provide measurements (e.g. see this product).

The cassette is 11t to 36t, so based on this answer I have these calculations:


Maximum Chainring Difference = 0 (there's only one chainring)
Maximum Cassette Cog Difference = 25
Total Drivetrain Capacity = 25
Maximum Cassette Cog = 36


Based on the Total Drivetrain Capacity, that would point to me being able to use either Medium or Long (my Maximum Cassette Cog exceeds the 34 limitation, but that answer is nine years old, and some comments indicate that 36 is pretty normal).

Of course Medium might be good in relation to ground clearance, but I might be tempted to go for Long if that's what I have already. What cage size do I have, and is there physical measurement data available that I could have used to answer this question for myself?
That linked answer is great, but the lengths of derailleur cages have been increasing with successive generations, so those figures are out of date now.

You need to consider the size of largest cog which the derailleur is compatible with and compare the specs of the individual units.

Counterintuitively, the longer cage is actually compatible with the 36 tooth large cog you have, even though this 36 is smaller than many around today. The medium  cage M6000-GS is suitable for cassettes where the largest cog is a 42T, while the long cage M6000-SGS works with cassettes where the largest cog is in the range 32-36 teeth. If you were choosing between these two, then you would choose the SGS long cage

There's every likelihood that your bike currently has the RD-M7000-10-SGS for the same reason (also its the 10 speed one).