They are extremely wide tyres you are trying to fit , not something I think you will get away with stock arches , common sizes to run are 245/255 upfront / 275/285 rear
Nic was running 18x9 +32 245/40R18 and 18x10+32 285/35R18, the wheels sit almost flush with the stock wheel arches, the arches needed slightly rolling so the tyres wouldn't catch.
Rim width Minimum tyre width Ideal tyre width Maximum tyre width
5,0 Inches 155 mm 165 or 175 mm 185 mm
5,5 Inches 165 mm 175 or 185 mm 195 mm
6,0 Inches 175 mm 185 or 195 mm 205 mm
6,5 Inches 185 mm 195 or 205 mm 215 mm
7,0 Inches 195 mm 205 or 215 mm 225 mm
7,5 Inches 205 mm 215 or 225 mm 235 mm
8,0 Inches 215 mm 225 or 235 mm 245 mm
8,5 Inches 225 mm 235 or 245 mm 255 mm
9,0 Inches 235 mm 245 or 255 mm 265 mm
9,5 Inches 245 mm 255 or 265 mm 275 mm
10,0 Inches 255 mm 265 or 275 mm 285 mm
10,5 Inches 265 mm 275 or 285 mm 295 mm
11,0 Inches 275 mm 285 or 295 mm 305 mm
11,5 Inches 285 mm 295 or 305 mm 315 mm
12,0 Inches 295 mm 305 or 315 mm 325 mm
12,5 Inches 305 mm 315 or 325 mm 335 mm