We’ve read the reviews across the web for the SRAM X01 Eagle 12-Speed Rear Derailleur and summarize the results below:
Universal Ranking
PeakScore: 90 (out of 100)
User Rating: 4.4 stars 
Expert Rating: 4.8 stars 
Number of Ratings Reviewed: 52
Pros & Cons
Reasons to buy:
User Reviews
- Provides smooth shifting.
- Easy to install.
- Lightweight and high-quality material.
- A good number of gears.
- Shifting up and down is quiet.
- Looks great and stylish.
- It offers a wide spread of gears for versatility.
Expert Reviews
- Enhanced shift performance and durability from previous models.
- Long-lasting Ti-nitride finish.
- Downshift lever has a custom angle for versatility and adjustability.
- The foam core in the X01 rank arms makes the system resistant to damage.
- 10-50T gives a 500% gear range without any gaps or holes.
- The chain and cassette have high durability.
- Uses carbon fiber arms and alloy chainrings to remain lightweight, while keeping the stiffness.
- Great durability over hundreds of miles.
Reasons NOT to buy:
User Reviews
- Some reports of the chain getting knocked off the pulley, which shouldn’t happen for equipment at this high of a price.
- Some reports of the cranks seizing up, resulting in the chain falling off.
Expert Reviews
- Expensive, but is cost-effective due to the high gear range.
- Heavier and more expensive than other similar models.
- The B-tension has to be precisely tuned for optimal performance.
Summary:
The SRAM X01 Eagle 12-Speed Rear Derailleur is an adjustable and versatile apparatus that will benefit most intense cyclists. The cost and some durability issues may deter some, but for those who need an expansive gear range, clean shifting, and a lightweight piece, this is a great option.
Multimedia:
Note: User and expert rankings were reviewed across the web. Some expert reviews include these: 1, 2, 3, 4, 5.