SHIMANOAltus Mountain Bike Rear Derailleur - Direct Mount - RDM310

A great derailleur for the price, shifts perfectly and quietly and is totally silent while operating on all sprockets. It is easy to install with a just a few allen wrenches, I didn't bother taking apart the chain, I just disassembled the cage slightly to get the chain inside it. Adjusting was slightly more difficult. The only issue is that there are no paper instructions for installation and especially ADJUSTING it. It is essential to adjust the low and the high limits to align the upper jockey wheels and chain with the low and high sprockets, THEN just as importantly, when derailleur is on smallest sprocket remove ALL slack on the cable by pulling the cable tight when the cable attachment bolt is loose, then retightening the bolt, and/or by screwing the cable adjustment barrel until the derailleur just starts to move inward to the next gear. Maximum rear sprocket size is supposedly 34 tooth, and I found it best the adjust the B tension screw inward quite a bit (the one on the bracket that limits the derailleur front and back swivelling) to help the upper jockey wheel clear the larger sprocket (28 tooth in my case) better. Once installed and adjusted, it worked PERFECTLY every time.

My chain; shifter / cable; and likely the stock derailleur were all worn out on my bike. I replaced them all and chose this derailleur. I'm glad I did! Everything works perfectly together, and my bike shifts better than any bike I've ever rode before. (Proper setup is essential.)The negative reviewers only have themselves to blame because they evidently didn't know how to install and adjust a derailleur. Watch some videos and learn how to do it the right way, and you can also love this derailleur.

Paired this with a Shimano Altus right side trigger shifter, 7 speed. Installed this onto a Mongoose Ardor due to the cheap Pro Rush derailleur binding the chain up real bad when hitting a small jump or bunny hopping a little higher than an inch. Like, the derailleur would skip the chain off one of the pulley cogs and it would stick between the metal guides and the cog. These two, once installed and tuned, are tuned to work perfectly with each other. My derailleur hanger was checked with my Park Tools DAG alignment tool, and the derailleur hanger wasn't really bent hardly at all, but it doesn't hurt to ensure good hanger alignment before installing any new equipment.This derailleur is working fine on the Pro Rush freewheel 7 speed gear set, since it's paired with its proper Shimano Altus shifter counterpart. That's where people mess up, is pairing a new derailleur like this Shimano with the older shifter like the Pro Rush that was on the bike. I'll update the review if the Shimano Altus just breaks or craps out, but the first ride out it shifted very very nicely, and even handled several little jumps with no chain slippage or binding. I just am not ready to upgrade the rear wheel to a free hub with higher than 7 speeds, so finding this derailleur and shifter combo worked out great. :)

Worked great, fix my shifting issue on my Giant Escape 3. Finally smooth shifts and can use all my gears. Since I purchased the bike, years ago, no matter what I did to tune the back derailleur, i could not get my old derailleur to align with all my rear gears. Either 1-4 or 5-8 somewhat usable, but never all or with out slipping teeth on hard peddling. I tried countless times to tune, thinking it was my lack of skill. I was about to buy a new bike. After replacing with this direct replacement ( replaced my chain too since I was replacing this derailleur ), finally, the bike is working as it should! No more skipping or clickity-clack sounds ...now smooth, easy to engage gears, no more slipping when applying heavy pedal pressure...feels solid now.

This derailleur is pretty decent and is a cost effective and performance worthy piece of machinery.I chose this over Acera for price and performance. It is a little heavier. However, I feel that the performance is smoother and more accurate than Acera. In past experience, I found that Acera has less chain retention and is a little more snappy. This Altus is a bit more precise and smoother. This makes it an ideal upgrade or replacement.I like the larger lower pulley for the increased chain retention and quiet shifting. Also, like most Shimano derailleurs, it is easy to set up.For the price and quality, I see no problems here. Personally, I don't like the blobs of bright green grease used in the ends of the parallel spring. This is more of a minor annoyance. If you ever do trail rides, you know what I mean. However, I remove the grease with a small flathead and leave a minuscule amount. I wish I could rate this a 4.5 rather than a 4.Overall, it's really good for its quality and price. I highly recommend this for your needs. I will buy again.

If you're looking for a wide-range derailleur that's safe to use with small wheels, this is the one. I got this for a recumbent trike with 20" wheels because the stock derailleur got dangerously close to the ground in some gears, but I didn't want to give up my large hill-climbing winch gears. This derailleur solves that problem with extra-large jockey wheels, which allows Shimano to shorten the cage and improve ground clearance without sacrificing capacity. The price is fantastic, and after several years and ~10k miles of mixed riding it still works beautifully.What makes this derailleur really special is that, while it doesn't have the highest capacity around, it's the only wide-range model I know of that supports both small wheels *and* front derailleurs. If you're looking for low gears, that's an incredibly powerful combination, with gear inch ranges rivaling high-end gearboxes and gearhubs costing thousands. And for ~$20! Best purchase ever.The only maybe-downside is it's only 8 speeds, but honestly that's good enough, and 8-speed chain is stronger, longer-lasting, and much cheaper than 10/11/12 speed chain, so that's actually another pro in my book.