Help me decide, XTR confusion !!

[KernzyP]

Hey guys.
Again, I thought I'd ask some experts for their knowledgeable opinions.
I'm having trouble deciding or at least KNOWING what derailleur to use.
I have an Exage 300 LX (long cage) rear derailleur, and it's bashed and twisted to hell, as is my hanger, although, still works! It came off my old Marin Palisades !!
I bought a new hanger and two replacement used XTR's from Ebay. An RD M971, and a M986. Pretty sure the M986 is a medium cage. How do I tell? Very similar, but one is shorter, somewhat.
I prefer a long cage, but the seller sold the M986 with a 10 speed cassette, and said they worked together.
My bike is an 8 speed freewheel MTB.
I love the look of the M971, but the M986 has been fitted with a "Oneup RAD" green cage, which matches my bikes colour, which is nice.
971 is a 9 speed, 986 is a ten speed. I've been looking, and people say they will both work with my 8 speed freewheel. Is that true? I just ordered a new 8 speed chain, too.
It's not like the 1990's when we could swap almost anything with anything. It was either exage, or it wasn't!!
Now it's a damn scientific equation !!
Your advice will be well received. I'm already grateful for being around you guys.
Thank you very much in advance.
All the best,
Kernzy.

P.s., Even finding the correct hanger took me two days!! I'm old, now, just started riding again while suffering with PTSD. Pimping it up to increase exercise attraction.
Cheers.

 

[KernzyP]

Out of interest, the Exage derailleur has been spun up vertical into my spokes a couple of times. I had to take off my hanger, and bang it straighter with my D-lock on the edge of a kerb!! Otherwise, walk home 3 miles. Also had to bend the derailleur back a couple of times. Amazing it still works. Happened a couple of times, lost a spoke when it happened at high speed. Very scary for back wheel to lock up in London traffic, after hearing that spoke twanging "steel harp" chorus, lol

@STILL_ALIVE

 

[KernzyP]

HAHAAA!! Just realised, I very well needed the DORK DISC, LMAO!!

 

[bikeworkshop]

You can't run the 10 speed m986 with 8 shifter and cassette. wrong cable pull.

But you can run the m971, tail end of 9speed, compatible with 8speed cable pull.

You should still check hanger alignment if you've fitted a new one - it needs to be bang on.
Shops have a tool, you can make one up with a 10mm axle.

Your derailleur probably went into the wheel because the low gear stop wasn't adjusted right, worked loose, or due to derailleur or hanger misalignment.

It's a lot cheaper to fix it before it goes into the wheel

Beforew 1st ride, always check in 1st gear you can't push the derailleur further in so the chain comes off the sprocket!

 

[ishaw]

9sp Shimano rear mechs work with 8sp and 7sp too I think as cable pull is the same. If you want to use the 10sp you'll need a 10sp shifters as this is when cable pull changed. Depending on your hub, you might be able to fit the 10sp cassette, as it's running 8, I 'think' you should be fine to do this. You'll need a 10sp chain.

 

[Retrorockit]

The Shimano 10/11s derailleurs ended up using the same cable pull as SRAM 1:1 shifters, so retrofit SRAM X series shifters for 8/9s. This gets some gripshifter options that Shimano didn't offer.