Originally Posted by
Koyote
Good question. We'll see.
Even on a road bike, I would prefer (at age 58, and living in a VERY hilly area) something smaller than a 34...And I have no use for a 50. 'Course, I suppose I can always run GRX on a road bike -
what's to stop me? 
The rings I purchased pushed the chainline outboard by 2.5mm. I believe the GRX cranks do the same.
I've seen it mentioned that you also have to adopt the GRX Front Derailleur due to this 2.5mm.
I was stuck with my Ultegra Di2 FD and it would not accommodate the 2.5mm difference.
So there you go.... that'll stop yer if you're running Di2
Barry