Zee M640 SS cage derailleur with 11-40t cassette

Retrorockit

Retro Guru
Why the M640 Zee SS cage? It's a DH rated part. No plastic. The clutch cover and lever are both metal. The SS cage helps keep it up away form curbs and things on 26" bikes. This test confirms it works with up to 40t cassettes in 1x setup.
Also 10-11 speed Shimano comes out at the same cable pull as SRAM 1:1 shifter. So using those shifters 7,8,9,10,11 speeds can be done with this. Including gripshifters and even vintage 1/2 pipes.
The bike is a 2004 XC Softtail MTB. I converted it ti 1x11 as part of a front Freewheel conversion ( whole separate story) and the SLX derailleur hanging down was driving me nuts (as do all vintage 26" bikes with SGS long cage derailleurs).
The SLX can run up to a 51t cassette (I've done it).
The M640 comes in 2 versions DH for 11-28 cassette, and Freeride (FR) version with a different hanger extension for 11-36t cassettes. I bought the DH before I knew about the FR, so I got the FR hanger extension also.
I pulled off the SLX, and with the FR hanger it bolted right up, and adjusted in with the stock B screw. I didn't have to cut the chain either. It was already the right length going around the big cog. Now in the top gear it should be running just the way Shimano intended. But I didn't like the way it only wrapped less than 1/2 way aroung the 11t cog. If I don't like the way Shimano does something I tend to fix it. So I got the DH hanger and stuck it in there. The guide pulley was still some distance below the 11t cog, but it wrapped around to the front further for some improvement. But now it did need a slightly longer B screw. I pulled one out of a Deore I had sittting around and that was enough.
I didn't measure the SLX, But I do have an XTR M960 mid cage on another 26" bike with the same size tires. The XTR has 6" ground clearance in the worst gear, the Zee has 7".
I've seen claims the M640 can run an 11-42t cassette. I think the FR version could probsbly do that.
 
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I found an NOS Prestacyle HG11 cassette in 11-42t for a discounted price on Ebay. I've seen posts at MTBR that this works with the M640 Zee on a hardtail.
1- The Zee SS cage is rated for 29t capacity, so this is only a 2t stretch there.
2- I have a 42t chainring mounted. This gets me to 1:1 low gear, which has always been good enough for my purposes.
3- These are 2 piece CNC cassettes. The top 9 sprockets are hollowed out forged heat treated Chromoly. They will be the same. The 2 lowest sprockets are CNC 7075 alloy. So I will have spares now. Only the 40t/42t sprocket changes
4- These are lightweight parts. The PC 11-34t steel cassette weighs 292g. The 11-42t weighs 265g. Compared to the Shimano SLX/ Deorestuff at 467g. But those are much more affordable. Even at almost a 50% discount.
5- The tricky part will be if I need to add a link to my 11s Wippermann chain to make this work.
 
It's mounted and working.
1-- My chain was already as long as possible. In 11t the derailleur is folded up and almost hitting the cable arm. tension is good.
2- The longer B screw from another derailleur was just long enough. It's working perfectly, but an even longer screw wouldn't hurt.
3- A 2 tooth increase = 1/2 link in chain length (! hole). The chain warps 1/2 way around the cog, so only one more tooth engages the chain.
4- I actually used the DH version Zee. 11-28t rating. so I'm 14t over listed capacity. The Zee FR version (11-36t)has a different B link, the. same part# as SLX . I tried it but liked the DH one with a longer B screw better.
5- The Zee is very easy to set up with the chain off. The guide pulley doesn't swing around with the derailleur cage. It's mounted right on the same pivot. You can swap B links, and B screws, and cassettes easily.
Thew 1:1 low gear is useful to me, everything else is just the same. My cassette is zip tied to the spokes for the ENO front freewheel mod. The 2 piece cassette makes it easy to lash down the rear piece by itself. I didn't do it that way before. I took a couple photos
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1753494313485.webp
 
just to complement your thread. :)

Zee FR with 11-40T, working flawlessly without any modification.

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67e6c23cb8beb556bb93170a.jpg
 
The FR will do it easily. But the DH being further forward wraps around the small sprocket more.. I had both B links on hand and made my choice. Is that a black Sunrace cassette? Your photo definitely looks better with all new parts.
Your BB7s are showing!
 
I ran their 11-40t x 8s on my 1500W urban Ebike. Never a problem. But Shimano came out with one that has the 2 big gears riveted to a spider for $10 more.
I'm running BB7s on it too. Icetech rotors, metal pads, and full metal jacket cable housing setup.
 
The Zee was marketed for DH and FR bikes. Those are full suspension and the Shimano specs. have to allow for chain length variance due to suspension motion, which can vary from bike to bike. On 1x hardtails it's actually a rugged, compact, versatile derailleur.
The SS cage seems to be the limiting factor in cassette size. 20-24" bikes could benefit from increased ground clearance.
 
For most users the FR version will be the correct choice. But when I try things I'am also doing research for my Ebike. So the chain wrapping around the small cog more is significant to me. I did a Front Freewheel conversion on the mid drive Ebike (hint-the front freewheel is already there). It was a great benefit, but it ruined my shifting/pedaling coordination, so I had to do it to the XC bike also. I actually enjoy these mechanical challenges. So my other bike influenced my decision on this one.
 
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