Shimano 6800 rings on R8000 crank with Di2?

[DRZRM]

So I'm jumping into my first Di2 experience on an incoming gravel bike (thanks Clean39) and I have a Ultegra 6800 36/46 crank (actually I swapped to a 34/46) that I was going to use. I've learned that the spacing on the R8000 rings is different (.4 mm wider) and that the 6800 cranks will work with a R8000 FD but not the other way around. Is that also true for Di2? An I OK with a 6800 crank? If not, can I put the 6800 rings on an R8000 crankset? I know the color is a bit off, but is there any issue of chain line or mounting? Or do I need to buy a R8000 with the newer rings?

Actually I just looked at specs, and it has a Di2 6870 FD so all this is moot, right? That is meant to work with the 6800 crank? Sorry for dumb questions, this is my electric shifting bike, just want to make sure it will work as intended. Will a R8000 crank not work with optimally with the Di2 6870 FD? Did I luck into the perfect setup?

[Gummee]

IIRC they moved the rings outboard on the new 8000 stuff for better chainlines with 12x142 rear wheels.

Also IIRC the distance between the rings is the same.

Set the limit screws right and ride it

M

[Clean39T]

So I'm jumping into my first Di2 experience on an incoming gravel bike (thanks Clean39) and I have a Ultegra 6800 36/46 crank (actually I swapped to a 34/46) that I was going to use. I've learned that the spacing on the R8000 rings is different (.4 mm wider) and that the 6800 cranks will work with a R8000 FD but not the other way around. Is that also true for Di2? An I OK with a 6800 crank? If not, can I put the 6800 rings on an R8000 crankset? I know the color is a bit off, but is there any issue of chain line or mounting? Or do I need to buy a R8000 with the newer rings?



Actually I just looked at specs, and it has a Di2 6870 FD so all this is moot, right? That is meant to work with the 6800 crank? Sorry for dumb questions, this is my electric shifting bike, just want to make sure it will work as intended. Will a R8000 crank not work with optimally with the Di2 6870 FD? Did I luck into the perfect setup?FWIW, I've ridden it with both 6800 and R8000 cranks, both 50/34, and noticed no difference. Di2 is wonderfully robust and the shifting accuracy is kind of addictive..

Sent from my Pixel 2 XL using Tapatalk

[dddd]

6800 big rings may not have all of the outer surfaces aligning with adjacent surfaces on the 8000 crank arm, at least that was my experience when using 9000 rings on an 8000 crankset. It was more of a cosmetic issue than functional, there was a deep step at two of the arms.