Quoting ET's is pointless without quoting the wheel width to go with it. Et is the distance between the imaginary centreline of the wheel to the inside mating face, so two wheels could both be ET40 but if one wheel is a 6X15 and another is a 7X15 then the 7inch rim will stick out half an inch further inside towards the suspension and also outside towards the arch.
Exactly what I was going to say...
Two choices really,make the car fit the wheels or remove them.
Think like this...
Et 0 is the wheel centered on the centerline.
Et + pushes the wheel face in.
Et- brings the wheel face out toward you're arch.
If it were Et 0
And the wheel went from 6j to 7j
You have added 1/2 an inch either side of the centerline without changing Et.
Let's say(using you're example) you have went from 6 to 7j,and from +52 to +42...
1/2 inch plus the 10mm from the Et..
Assuming you are using the same Tyres would take it 22mm closer to the arch.
Try a lower profile tyre and roll/pull the arch slightly.