great

no weakness

sfift very fast and well

Reliable, easy to use

Appearence

I had my Trek 3900 since 2010 (review written in 2012) and it has Shimano Acera on it. The large plastic shell protects and covers, but isnt the best for appearence. Ive never had a problem with my rear derailler thanks to Shimano Acera. It awlays shifts smoothly, and is a lot better then my moms Sram rear derailler which lets the chain awlays fall of the teeth and is very unreliable. I would highly reccomend this product to a friend.

shifts DECENTLY but i always hear grinding,and there are constant misshifts where the chain pops off. I always wash my bikes and lube all the parts right affter i hit a trail.

Today I was bunnyhopping in my neighborhood and my chain slipped to a different gear,like always i just tried to pedal and hope that it would correct itself. but this time it was different when i pedaled the whole derailer twisted and got caught in my spoke and the plastic part snapped in half.

It never worked well from the beginning. There was always rough shifting misshifts and the chain even came off several times and the final straw was when it snapped in half in my back wheel....I really expected more from shimano.... I ride on very harsh trails but at the same time i always take my time to maintain my things.

Similar Products Used:

None

Simple, surprisingly strong on the trail

Plastic, integrated with brake lever, optical display

I bought the bike for an around the city kicker but it got me into mountain biking. For a year, this whole set has been trouble free, set it and forget it. I love it. I hate the plastic and gear display, but its an amazing value. I've jumped, crashed, ran rabbits over, and far more, nothing has happened to them.

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alivio

I've had this model of derailluer for over 1 year. It is obviously not a performance part but it does well.

I ride hard, downhill and all-mountain trails, pushing my limits. I've gone through 2 of these derailluers. I know that for my type of riding I should invest more, but I'm poor and I don't need supreme performance. It does the job.

My first derailluer bent just from crashes and other stress. My second one just went 2 days ago when a stick got caught in the wheel.

I often lose performance because I don't replace my cables often, and they get gunked up fast. Cable replacements and cleaning the drive-train more often would get me more out of this product.

I'm surprised how well it does for what I do. Again it's not a performance part, but it's stood up to what I've thrown at it.

Weak hanger, incapable of maintaining a tune-up for 24 hours

I got this derailleur with the bike at a nation-wide sports store, but within two weeks of having the bike and riding it daily, it wasn't shifting properly, and in first gear it caught on a spoke of the wheel, and snapped the hanger clean off. I sent it back for the replacement as per the warrranty, and this store put another Acera back on. Again, I had problems with shifting, and I got so fed up with the problem, I took it to the store and said I needed it replaced, because I couldn't even make a tune-up last for a day on this derailleur. They claimed they had no other 8-speed derailleurs, and offered a free tune-up and cleaning/waxing of the bike. I brought it back home, the next day shifting problems again. I dealt with this for two years, and two weeks ago, the hanger snapped again after the derailleur caught on the spokes of my bike wheel (In 6th gear this time). In neither instances of the hanger snapping were my spokes damaged, not even paint scratched off. If your a non-serious biker, maybe 5 miles on the weekend, this derailleur will work fine for you, but anything more than that, you will unlikely be satisfied with the quality of the derailleur. I wouldn't recommend any serious biker purchase this product and expect it to perform even basic functions satisfactorily. I have gone through two of these derailleurs now, and both times they had the same issues. I maintain my bike very well, as I ride a minimum of 3 miles daily through every weather and road condition known to mankind, including rain and snow.

cheap, easy to setup

not the best looking, heavy

Recomended if you, want to use your bike under normal riding conditions, relaxing after a hard day at work for example

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Shimano Alivio

smoothe shifting, looks good, does good on a city commuter or for training

heavy scratches easily

Good compnent as long as your not on a trail but will buy ultegra on a road bike next time

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xti

Quick fast shift, was reliable and would avoid the biggest of hits

Broke very easily, plastic, not very appealing due to easy scratch

i would not buy for a cheap reliable great performing rear deraillieur pick a SLX much better, this one broke for me after a year of on off riding but completely gave up in deep riding, and has now snapped and bent the hanger along with a few spokes.

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Shimano SLX m600 shadow

Shift very well and fast.

It cage plastic design, heavy.
delicate

I got it 2 years ago, and works exactly like when i buy it.
shift fast and precise.
Be careful with this when fall down, because can be damage inside cage and not shows number of rings or shift bad.