Making a Shimano GRX 46/30 crankset and Shimano Di2 RD work with Sunrace 11-46 cassette

This project was more in the realm of "I wonder if it can be done", than "I absolutely need this" so please don't hate.... I know there are bikepackers out there who are always looking for more range, and we have some stupid steep double-track here.... so... I had the parts laying around, and figured.... let's do this... you know... for science.

Specifics:
Shimano GRX FC-RX600 11 speed 46/30 crankset
Shimano FD-R8050 front derrailleur
Shimano RD-8050 GS rear derrailleur
Sunrace 11-46 11 speed CSMX80 Cassette
Wolftooth Roadlink DM
KCNC 15t jockey wheel

The Roadlink and the 15t jockey wheel are imperative to clear the 46 and to take up chain slack in the small/small combo. Keep in mind that this will only work with a Di2 drivetrain as Di2 keeps you from shifting into the 2 smallest gears when in the small chainring. Chain length had to be perfect. One more link and I got slack in the small/small. One less link and it would not shift into the big/big, which you don't want to run, but better to set it up to work than to break a chain in the middle of EBE.

If this works reliably, I will probably replace the Sunrace cassette with a Garbaruk 11 speed 11-46. The Sunrace is notorious for shifting down the cassette if you back pedal, the Grabaruk does not suffer from this and is 210 grams lighter.

So far it works great.  Test ride Monday will report back.

I'd be surprised if that's an issue....  my wife runs a 50/34 with an 11-32 using a mechanical shift Ultegra RD on her road bike without any modifications and it runs just great.

You *MIGHT* have to fiddle with the B screw to pull out some slack, or depending on which generation RD you have, go to a larger lower pulley like I did. That's the part of the equation that fulfills.

Good luck and report back!!!

dangle wrote:How is the shifting from the 13 down to the 11 on your cassette?