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SRAM GX Eagle Rear Derailleur - 12 Speed 52T 520% Range [Rider Review]

Our "Rider Review" article series features the honest reviews from verified purchasers of Worldwide Cyclery. They contain the photos, thoughts, feedback & overall review you are looking for.

Needing more gear range in your riding? Would a bail out gear or being able to run a bigger front chain ring excite you? The new 520% GX Eagle range from SRAM will give you 52 reasons to consider why you should be thinking about those advantages. Our buddy, Chaz, has a real world review for you that's worth checking out.

Introduction & Background

My 2019 Stumpjumper came with a Shimano SLX 1x11 maxing out at 46 teeth on the low-end gear. It was honestly a decent setup with good, reliable shifting. But on some days, I need a bailout. Southern California is littered with steep climbs that make some people including myself, question this sport. Relatively new to mountain biking in general, having never tried any SRAM Eagle components and being a total “fraidy cat” with installing my own RD, I selected the new SRAM GX Eagle 12 speed rear derailleur w/520% revision. I also selected the SRAM GX shifter, SRAM GX 520% cassette, and of course a new SRAM Eagle 12-speed chain. I pulled up my big boy britches and took the hits like a champ.

Installation and First Impression

After a new wheelset to accommodate the SRAM XD driver, I was ready with my basic bike tools. Install day was longer than I expected. I have never replaced a rear derailleur before. Heck, I haven’t even re-indexed or diagnosed shifting issues before. I always took it to the local shop.

After watching an assortment of YouTube videos including one with Worldwide Cyclery’s own Jeff Cayley on SRAM Eagle drivetrain install and setup, I was ready to go. Except I wasn’t. I got anxious and cut the chain to the wrong size. After a couple of more days waiting for the new chain and correctly sizing it, I was ready. Go me.

I cannot believe how quiet the drivetrain is and how smooth it felt.

With the previous-gen 11-Speed Shimano SLX, I felt the ratchet effect travel up the shifter-reliable, yes - smooth, not so much.

Hot or Not?

Hot: 52t on the low end, 10t on the top end. Smooth, instant shifting even on big gear jumps. It feels expensive. Handy RD lock to take the tension off the chain when servicing.

Not: The jump from 42t to 52t might concern some. For now, I just spin more on the 52t, it works for me. Shimano’s 12-speed system has 39 to 45 to 51 on their big cassettes which might suit some better. Also, I miss upshifting using my index finger and downshifting using my thumb. The SRAM GX Trigger forces me to use my thumb for both, but I am adapting quickly. Also, one would argue that reserving the index finger to always being over the brake lever is safer.

Notes: I haven’t downshifted multiple gears on “full power” when faced with a sudden climb. I don’t know if it’s as forgiving as Shimano’s 12 speed is reported to be. I’m steadily ratcheting up how much power I’m applying while downshifting. I always find a way to fail at anticipating gear changes, so shifting under load is important to me.

The first few days of riding warranted fine-tuning considering I’m new to drivetrain installs. It wasn’t anything concerning. Just some basic things I did not consider fully. B tension on SRAM is critical. I eyeballed it. It worked, but having someone squat on the bike while I adjusted the tension with the SRAM B tension alignment tool made things even smoother.

Final Thoughts

The SRAM Eagle 52t cassette kept my cadence high and my slightly over-forked bike’s front end from wandering on steep climbs. The 10t on the top end makes the 1200 ft descent on the street back home from my rides really fun. Previously, I topped out at 11t. All and all, this was a worthy upgrade and good insight to the world of SRAM.