by BRIAN MULLIN

SEPTEMBER 11, 2024

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Offering a wide gear range and excellent shifting technology

KMC Chain USA released its first cassette design earlier this year. Available for 10- and 11-speed drivetrains, the REACT cassette features proprietary shifting technology that pairs well with KMC and other chains. It comes in 10-speed 11-36T & 11-42T and 11-speed 11-42T & 11-50T variants, with pricing from $38-$65.

Called Flow Control, the REACT cassette features dual shifting ramps for smooth and steady gear changes.

The ramped tooth profiles help lift and lower the chain during corresponding shifts, providing excellent shifting performance. The unique tooth profiles are wider to reduce friction and increase durability.

KMC optimized the cassette design for KMC chains and will also work well with other brands.

Several ranges of cog sizes are available, including an 11-speed 11-50T and 10-speed 11-42T, allowing riders to upgrade their worn drivetrain and significantly increase their gear range over stock offerings. The cog sizes are gradually increased for smoother shifting and precise chain indexing. The REACT cassette is compatible with a Shimano HG freehub body.

10-speed: 11-36T, 11-42T

• 1-36 (11-13-15-17-19-21-24-28-32-36 teeth), $38
• 11-42 (11-13-15-18-21-24-28-32-36-42 teeth), $42

11-speed: 11-42T, 11-50T

• 11-42 (11-13-15-17-19-21-24-28-32-36-42 teeth), $59
• 11-50 (11-13-15-18-21-24-28-32-36-42-50 teeth), $65

The GoatLink 11 hanger extension offsets the position of your 11-speed Shimano mountain bike rear derailleur, allowing you to run a broader range cassette while improving performance. The WolfCage (no longer made) was a modified derailleur cage with an eccentric pulley that replaced the stock 11-speed Shimano inner cage and its upper jockey wheel. The system improved chain wrap and derailleur capacity for the extended range setup.

Impressions

The tested 11-spd 11-50T cassette was installed on my fat bike’s HG freehub body without any issues. It slid effortlessly onto the splines and tightened like any standard HG-compatible cassette.

In my test, I used my existing WolfCage Derailleur Cage setup on my old XT 11-spd derailleur and later switched to the newer GoatLink 11. Both worked admirably to make the XT 11-spd derailleur compatible with the extended range 11-50T REACT cassette. Most of Shimano’s 11-spd derailleurs only work to a maximum of 46T cog, so the adapters provide the extended gear range of the 50T teeth.

The 11-50T features a range of 11-13-15-18-21-24-28-32-36-42-50, providing a uniform shifting pattern between the cogs, with no significant jumps or gaps in tooth count from consecutive cogs. The gear range gradually increases the cog sizes, allowing for smoother shifting and precise chain indexing. It would have been nice to have a 10-tooth cog, but the HG Driver doesn’t make that a compatible alternative. The 11-50T gear ratio steps worked perfectly without stuttering or big chunks between gears, neither up nor down.

The dual-shifting ramps control chain flow for smooth and steady gear changes. The lifting ramp design carries the chain smoothly upward on the cog, while the distinctive lowering ramps adeptly align the chain quickly. These technologies improve shifting performance and overall component interaction efficiency and stability. Even under load, the chain cruised upward and downward without any issues, and it always offered a decently crisp, hesitation-free movement in either direction.

I only tested it with the KMC X11 chain, and even though the cassette design was optimized for their chains, I presume it would be okay with any 11-spd chain brand. The X11 chain did its job admirably, and the X-Bridge technology, with its precisely chamfered plates, offers up smooth power delivery and perfect gear changes.

Measured Weights:

• KMC 11-spd 11-50T REACT 739g
• KMC 11-spd X11 Chain 256g

The 11-50T is heavy, but the high-strength steel construction with a special coating offers excellent rust prevention, incredible durability, strength, and performance. It’s one tough cookie!

Bottom Line

The KMC REACT cassette features proprietary shifting technology with shifting ramps for smooth and steady chain control, improved shifting performance and efficiency, and preferential gear range options.  The tough-as-nails (though heavy) specially coated high-strength steel construction offers a long-lived, durable, and affordable cassette. It comes in 10-speed 11-36T & 11-42T and 11-speed 11-42T & 11-50T variants, offering a slew of gearing needs for a broader range of riders.