Cannot say if the tyres will fit on the rim or under the mudguards, but the diameter of the wheel/tyre combination will be smaller than stock so your speedo will be out.Originally Posted by E34 Touring
A 225/60 x 15 wheel has a radius of approx 325.5 mm and your combination would work out to approx 318.6 mm. In other words the diameter of the wheel and tyre combo would be just over half an inch too small.
235/40 x 18 tyres and wheels would have a radius of approx 322.6 mm.
245/40 x 18 tyres and wheels would have a radius of approx 326.6 mm
What also has to be considered is how wide the wheels are and what the recommended tyre width range for that width of wheel is !
More info required please.
Edit : the other stock combo is 205/65 x 15 which has a radius of approx 323.7 mm.