Is the Ultegra 11-speed crankset compatible with a 12-speed groupset?
Not officially. The Ultegra 11-speed chainrings are designed for the 11-speed chain; with a Shimano 12-speed drivetrain (105/Ultegra/Dura-Ace 12-speed) the correct choice is the matching 12-speed crankset. Some people reuse it, but front shifting and chain durability suffer.
What you need — before you buy
- It depends on the exact parts: read the answer above and check the manufacturer's spec for your specific model and year.
- When in doubt, keep the same brand and generation across the components that must work together.
- Match the part to your exact hub/frame: check brand, model and year. Don't choose a freehub body or component by standard name alone.