Wolf Tooth Components GCX 42T Replacement Cog

Marshal Olson reviews the Wolftooth components GCX 42T Replacement Cog for Blister Gear review.
Wolf Tooth Components GCX 42T Replacement Cog.

Wolf Tooth Components GCX 42T Replacement Cog


  • Available for SRAM XX1 and X01 cassettes
  • Made in the USA from 7075-T6 aluminum
  • Available Colors: Black, Silver, Red, and Blue

Blister’s Measured Weight: 82g

MSRP $89.95

Tested on SRAM X01 cassette

Miles Ridden: 150

The SRAM XX1 and X01 11 speed cassettes are pretty much modern marvels of engineering. Their machining, performance, and weight are incredible. They’re also not cheap (they can be found for around $300), which is unfortunate for a drivetrain component that, by its very nature, is prone to wear out. That’s why the Wolf Tooth GCX 42T Cog caught my eye. Wolf Tooth claims that it offers “new life for your old XX1/X01 cassette.”


The 11 speed SRAM cassettes are assembled from 3 basic parts: an internal sleeve, an aluminum 42T big cog, and a steel 10-36T range “powder dome.”

SRAM’s steel cogs have proven to last many thousands of miles, as evidenced by the durability of the various 10 speed SRAM cassettes made from the same 4130 steel as the lower cogs of the XX1 and X01 cassettes.

Unfortunately, the aluminum 42T cog is much softer, and because it sees the most lateral load of any of the rings due to its offset from the chainring, its teeth wear out much quicker.

I usually begin to see diminishing shift performance going into and out of the stock aluminum 42T cog at around 600-700 miles of riding on the cassette. And by 800 or so miles, I end up shopping for a new cassette. Given the price of these cassettes, that is a major bummer.

When I first saw the Wolf Tooth GCX replacement 42T cog, I was excited. Its very reasonable $90 price tag positioned it as an affordable alternative to replacing my entire cassette. It also lined up perfectly with my X01 cassette that had taken a turn for the worse and needed some love.

I was skeptical, however, about how easy the install would be, and what sort of shifting performance it would offer.

Having ridden several 42T add-on rings for 10 speed setups,  I gravitated back to a proper 11 speed setup since I feel stock 11 speed cassettes offer markedly crisper shifting than the add-on setups. I was curious to see how this aftermarket 42T cog would stack up to the stock SRAM cog’s precise shifting performance.


Detailed step-by-step instructions are available here on Wolf Tooth’s website, but I’ll give you a quick rundown of the process.

To remove the stock 42T cog, gently pry with a big flat-head screwdriver between the 36T cog and 42T cog at each pin location. You will need to go around the cassette 2-3 times, moving the cog just a little each time. I made sure to fully support the cassette on the edge of a table, since I was concerned about bending the steel cogs. I was less concerned about bending the alloy cog, since it was going in the trash anyway.

The process went smoothly, and I popped the stock 42T cog off easily and without issue.

Marshal Olson reviews the Wolftooth components GCX 42T Replacement Cog for Blister Gear review.
Wolf Tooth Components GCX 42T Replacement Cog installed on a SRAM X01 Cassette.

To install the Wolf Tooth GCX 42T cog, align the large marked hole on the cog with the large pin on the cassette. Gently squeeze the cog and cassette together at each of the 18 pin locations with Channel Lock type pliers until all the pins are bottomed out. (I covered the pliers with a rag, so the cassette surface would not mar.)

Once the cog was on, I gave it a few taps with a rubber dead-blow hammer to ensure everything was nicely seated, and reinstalled the cassette on my wheel.

Marshal Olson reviews the Wolftooth components GCX 42T Replacement Cog for Blister Gear review.
Wolf Tooth Components GCX 42T Replacement Cog installed on a SRAM X01 Cassette.

All told, the process probably took about seven minutes, and was very easy to accomplish. I do wonder how many times it can be repeated without damaging the small flanges on the cassette that the 42T cog press onto, but given how much softer the alloy cog is, I feel like at least a couple more rounds aren’t out of the question.

Shifting and Performance

With the wheel back on the bike, I installed a fresh chain and ran through the gears. There was no need to adjust the derailleur. The first few shifts through the range and onto the 42T cog felt a bit clunky and loud, but everything settled perfectly after five minutes of riding around my driveway.

Once on trail and shifting under load, I felt no noticeable difference between my original cassette back when it was new and the Wolf Tooth GCX.

I now have about 150 miles on it, and have yet to notice any performance difference from a stock SRAM cassette. That’s great in my book, since the crisp shifting performance of the SRAM 11 speed cassette is what sold me on it in the first place.

Bottom Line

If you are running a SRAM 11 speed drivetrain with an XX1 or X01 cassette, replacing the stock 42T cog with the Wolf Tooth GCX once you start losing shifting performance is a no brainer. There just isn’t a downside, and it saves you $200 or so over purchasing a new cassette.

The lower priced and slightly heavier SRAM X1 and GX 11 speed cassettes use alloy 42T cogs like their more expensive brethren, but these cogs do not yet have a replacement solution, so one could argue that the X01 cassette actually represents a better long term investment when combined with the Wolf Tooth GCX 42T cog.

In my mind, the Wolf Tooth GCX represents the final step forward in 1×11 drivetrain dominance. Chains don’t drop off modern narrow-wide rings, 10-42T cassettes offer a wide range, and now the weakest link in these sweet and highly machined cassettes can be rebuilt and run long term.

With the GCX 42T cog, Wolf Tooth has developed a product that riders actually need and benefit from, and then made it available at an affordable price.


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