bootsie_cat wrote:
You can mix, but why would you? Unless you are going to put the 9170 brake/shifters on later?
You can get XTR 9000 calipers pretty cheap and they are excellent brake calipers. I have used them on my fender bike and cross/gravel bike for 2 years.
XTR calipers are post mount not flat mount though. You could use them with an adapter, but that kind of defeats the purpose of having a nice clean looking flat mount fork/frame.
If you can wait, I'd go with Ultegra 8070 brifters. The R785 brifters are pretty bulky, whereas the 8070 brifters look and feel almost exactly like the rim brake version. And it looks like they can be found for $500-$600 for the set. I don't think there's a definite date of availability yet, but I'd imagine they'll be out there before springtime since they're starting to make their way into OEM now.