Is it possible to use a rear M975 XTR IS mount caliper to to run a 180 mm rotor on an IS mount fork without an adapter?
Looks like it may have been answered in 2004. (Yes)
Best way to run 180mm on XTR calipers
Can anybody confirm.
Yes all Shimano IS 160 rears are 180 fronts, and 160 fronts are 140 rears.
If I disagree with you, it's because you are wrong.