Interesting, I get the same on the C3 - rubbing front brake after or during long descents and hard braking. Usually I just have to tap the brake level slightly a couple of times for it to go away (without the pads even touching the rotor), so I chalked it up to heat causing one of the pistons to stick slightly, perhaps due to dirt. I'm going to have to try one of these axles. The brakes I have are Shimano R8000 with SM-RT800 160mm rotors.