I had the same issue with the mxus 3k.
On the frame I was using, just a couple of thin spacers/washers between the frame and brake adapter worked. Also, used a rotor spacer. I don’t know if it’s mentioned yet, but several people shave off the mxus 3k raised emblem that’s on the side plate cover that causes the clearance issue. I didn’t go this route, because I actually like the look of that emblem. Although everyone seems to end up with a scratched side plate from the brake caliper eventually.
So I think it’s easier just to shave the emblem off considering when you use a 203 mm rotor you can’t really see it anyway because it’s hidden behind the rotor.
Someone please tell me why after all these years they have not changed this on the mxus 3k? Crazy right, it’s not like this is a new issue. But yeah, that being said, I do really like the mxus 3k motor itself. It can handle a decent amount of current and it’s not as heavy as the QS205, which is a huge plus for mountain bike frames.
If anyone’s curious of max current with this hub motor, I was using 60amps but I had to keep a close eye on the temps. Was using F/F with hubsinks and ticker upgraded phase wires. that was at 72 V rated, so around 4 kW
