1×11 Salsa Cutthroat GRX600 Upgrade to 11-51 Cassette with Garbaruk Rear Derailleur Cage

A couple years ago I bought a 2022 Salsa Cutthroat GRX 600 1x (link to the exact bike). As the name implies, this is a 1×11 drivetrain with a Shimano GRX RX812 for the rear derailleur and an 11-42 cassette. As I’ve learned more about bikes I realized this is a pretty bad gear range (~382%), which lines up with my experience. On a bike trip last year, there was a section with some pretty serious hills, and I struggled getting up some hills with a loaded bike.

I started looking for ways to increase the gear range–ideally with a low gear around 20 gear inches for difficult climbs–while maintaining my current high gear. The GRX RX812 supports a maximum of 42 teeth, so simply swapping the cassette to something with a wider range was not an option. I was tempted to upgrade to a 1×12 drivetrain like on the newer Salsa Cutthroat, or upgrade to 2x, but the cost and complexity of doing so dissuaded me.

This led to a search for a cost-effective solution to get a similar gear range to the newer GRX 610 systems that I could install myself. Unfortunately this search led to a lot of dead ends, the most promising of which was the e*thirteen 9-46 cassette with a 511% gear range, and which several people on reddit mentioned works with the stock RX812 derailleur despite 46T being larger than the officially supported range. This is when I learned about the wonderful world of bike part compatibility; my free hub is Shimano HG and is not compatible with the XD/XDR hub splines required for the e*thirteen cassette. I explored several other options:

• Upgrading my rear hub to XD/XDR to be compatible with the e*thirteen cassette
  • Cons: requires rebuilding the wheel, plus people online report mixed results in shifting to the 46T ring with the RX812
• Upgrading the rear derailleur to the GRX RX822 12-speed but continuing to use my current shifter
  • Cons: seems hacky, with mixed success in the comments of these sources

Ultimately I landed on the decision to get a Shimano HG 11-51 cassette (CS-M5100-11) compatible with my current hub, and upgrade the rear derailleur cage using the Garbaruk GRX 11 speed derailleur cage. Garbaruk says this derailleur cage allows GRX 11 speed derailleurs to handle up to 50 teeth, and is relatively cheap (around $65 at time of writing). This led to an all-in cost of about $130 for the cassette and the derailleur cage.

I’m relatively new to bike repair/modification, as I only started a couple years ago when I got the Cutthroat, so the process was a bit intimidating for me. The process involved the following steps:

1. Remove the old cassette, install the new cassette
   1. Tools required: cassette locking tool, 1” wrench, chain whip (I didn’t have one so I used a glove and held the cassette with my hand)
   2. Video tutorial
2. Size a new chain
   1. Since the rear cassette is larger, a larger chain is needed
   2. Tools required: chain break tool
   3. Video tutorial
3. Modify the rear derailleur cage
   1. Tools required: hex keys, screwdrivers
   2. Video tutorial
4. Install the new chain
   1. Tools required: master link pliers
   2. Video tutorial
5. Readjust the rear derailleur
   1. Tools required: hex keys
   2. Video tutorial

Ultimately despite my nerves and lack of experience, everything worked out well. It took me most of a day, but I was able to make all of the modifications in a single day. After the job was done, shifting was smooth in the bike stand. I took it out for the first test ride today and the shifting felt smooth out on the streets too (I couldn’t feel much of a difference from the stock setup). I’ll update this post in a month or so with a longer-term review of the setup and its reliability.

After I had already ordered the parts, I did find another option that seems viable, cheap, and uses all Shimano parts: swapping the rear derailleur cage with a Shimano XT cage https://www.youtube.com/watch?v=ynpFsE8snww. If I had known about this option, I probably would have chosen this since it’s a bit cheaper, but so far I’m happy with my decision.

Since I’m new to bike modification I wanted to share my story and process in case this information is helpful to anyone else. Thanks all!