If the bike uses rim brakes, moving from ETRTO451 to ETRTO406 means that the brake pads should be lowered by 22.5mm, that's a lot.
I doubt its possible and anyway increasing the brake arm length bu 22.5mm will have a negative impact on braking power.
If there are road brake calipers, they also limit the tire width to 28mm for most of them.
A solution could be to change the brake calipers for long reach calipers (there are still some models available).