RD-M640 Zee Shadow Plus 10 Speed Rear Derailleur

It's well made, nice and compact and although the specs say that the biggest rear cog it can handle is a 36T it can actually take a larger 42T cog especially on a hardtail bike (due to a lack of suspension induced chain growth). I am running this derailleur on a 14-42T rear gearset. Another thing that can be done, either by use of a spacer or by drilling a hole, is to make this ten speed derailleur work with a 9 speed cassette/freewheel. I currently have it working as a 9 speed derailleur. It's a lovely derailleur and it's compact size makes it ideal for use on small wheeled bikes such as folding bikes. I hope Shimano continues to produce it.

Es un muy buen componente, llevo usándolo más de dos meses y ha resultado de muy buena calidad

Using the free ride version on my folding bike (11-32) due to the short cage. Shifting performance is great, short and precise. Not cheap but worth it.

It's awesome to get the same build/design quality of the pro-downhill level derailleurs at a non-pro price. This thing is fairly bulletproof in it's build quality, has a great clutch system to keep my chain from dancing, crazy easy to install with a new chain, and shifts smooth. Being it's not original equipment to my rig, my cassette is such that I have to really watch out for straining my transmission (running a 2x chainring). YES, it's an older bike, but just try and catch me on a downhill. It's not what you have, but how you use it!

This was a lot cheaper when I bought it a few years ago. It is just great. Shame how much it costs now. It's almost still worth it. 10 speed Shimano is basically dead but I'm locked in and loving it. Shifts every bit as good as 10 speed 105, and has the clutch. Super low profile too. Almost looks like an 80's derailleur with the tiny cage. Perfect for a suburban commuter or anything else really. I hear it's been discontinued, another terrible decision by the bike industry.

we Great derailer. It works with my 34 tooth cassette and 30 tooth chainring. Select the part number for 36 tooth cassette. The photos shows it fitting and a 20 inch wheel diameter kids bike. The cage clears the fat 20x 2.8” tires. The derailer keeps the chain on the gears over bumps even with clutch off. There is a slight increase in pulley friction drag with the clutch on and in the largest cassette gear. So my kid rides with the clutch off. Still is a large decrease in chain slap over the stock derailer.