Now to be more topical, since I'm willing to give you a second chance.
18's on a e30 are huge. You will need a very aggressive suspension and fender rolling to fit large wheels and tires. My old e30 wore 18x8.5 wheels with 245/35R18 rubber all around. I had the fenders front and rear rolled to the absolute max you can before you start flaring the metal outwards. There was NO room for addition wheel/tire width on either side. You could not fit a sheet of cardboard between the tire and wheel well tub on the inside, or the tire and inside fender lip on the outside.

Fitting a 9.5in wide rear wheel will require serious flaring and clearance of the fender arch. There is zero room on the inside so that full extra inch of wheel with will have to go outwards. This will leave you with about 3/4in of wheel past the outside edge of the fender lip. Proper tire size for a 9.5 is 265 or 275. Fitment issues entirely aside I don't understand why you would want that much rubber/grip on a car you don't want to be sliding.
18's on a e30 are huge. You will need a very aggressive suspension and fender rolling to fit large wheels and tires. My old e30 wore 18x8.5 wheels with 245/35R18 rubber all around. I had the fenders front and rear rolled to the absolute max you can before you start flaring the metal outwards. There was NO room for addition wheel/tire width on either side. You could not fit a sheet of cardboard between the tire and wheel well tub on the inside, or the tire and inside fender lip on the outside.

Fitting a 9.5in wide rear wheel will require serious flaring and clearance of the fender arch. There is zero room on the inside so that full extra inch of wheel with will have to go outwards. This will leave you with about 3/4in of wheel past the outside edge of the fender lip. Proper tire size for a 9.5 is 265 or 275. Fitment issues entirely aside I don't understand why you would want that much rubber/grip on a car you don't want to be sliding.

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