I built up an allroad/gravel bike back in 2022, when I thought the use case would include more road riding. I now have a separate endurance road bike and am doing more rugged gravel riding with this bike. Unfortunately the Ultegra 50-34 and 11-32 gearing is not low enough for some of the roads I’ve tackled recently (also getting older). Would it be possible to just swap out for a GRX 46-30 crank and a 11-34 cassette and keep the rest of my groupset (obviously moving the FD down the seat tube)? Or would I also need the GRX front derailleur? This is mechanical shifting, R8000 setup
Could I still use my Stages power meter on the left, non-drive side, or would it be uneven with the GRX drive-side arm?
The GRX crankset has a +2.5mm chainline so your existing FD may not be able to shift out by that much - it really depends on the frame. Many have been able to just swap cranksets and push out the FD with limit screws.
I run a toggle type Ultegra front derailleur (I think it is an R8000 series) on a 2x11 Shimano drivetrain, with a GRX crankset. I am using an XT 11-40 cassette with it, and a Clutched ultegra rear derailleur.
It works well.
I don’t know about the power meter thing, I have never attempted to mix-and-match crank arms.
Forgot about this part. The GRX crankset Q factor is 5mm more than Ultegra so each arm is shifted outboard by 2.5mm. If you use your left Stages arm it will work but your left leg will be 2.5mm closer to centerline than your right. Whether you can take up this difference with cleat placement depends on your current setup.
You may or may not notice the 2.5mm difference between left and right, and it might even be better that way - give it a try.
Assuming you have the longer cage Ultegra RD it will be fine with 11-34; 11-36 or 11-40 might also work. You definitely shouldn’t need - or use! - a Roadlink with 11-34, and most likely would get away with larger; my 2017 Sequoia came stock with a Sunrace 11-36 cassette, and this shifted fine with a 5800GS RD. (That same RD - rated for 32T max - also just barely worked with an 11-40 cassette.) Also, FWIW, I had 42x27 rings and an 11-40 cassette with an R8000 FD and Ultegra RX RD and ALL the gears had okay chain tension.
The FD might well be fine too; I’d give it a try before buying anything else.
I did this exact swap over on a Giant TCR. Removed the R8000 52-36 chainset and front derailleur, replaced with a GRX 810 48-31 chainset and front derailleur.
Bike already had a 11-34 cassette. New chain, new gear inner cables and bike shifted great.
Owner wanted the swap for a trip to Mallorca to make the uphills easier. He was very happy and feedback that the gears worked perfectly for his trip.
