3.0i, with 18" wheels. Like all 18's, and all 19" fronts, they are 48ET. I've never understood the exact use of the BMW ET #, but I do know that it describes the distance from the wheel's hub facing, to the outside edge of the rim. The rear wheels from a staggered set of BMW 19's or 20's have an ET of 45. Because the E53 X5 has hub flanges that stick out to the same point on the front as the rear, this means the wheel's outside rim edge will push out 3mm more.

I also know that when one buys wider BMW wheels, ALL of the extra width goes to the inside of the wheel. The car gets fatter.. underneath. They do not push out to the outside more. The ET numbers remain the same.

I'm about to go from 18"x8.5 all around, to Style 132 19"x9" all around. The ET is still 48. The extra half inch will pooch to the inside of the car. I'm adding 30mm wheel spacers to the back for sure (for looks). The question is, should I add wheel spacers to the front (again, this is for looks), and if so, how many mm?

Wait.. there's one more factor to consider; Wheel spacers push the wheel facing out, which means the push the steering axis point out too. The farther out the wheel's center line is from the steering axis, the more "dead" it will feel in steering.

I'm thinking about going with 10mm spacers in the front and that the steering axis to wheel center line point won't be effected, because my new wheels will be 1/2" wider to the inside. 12.5mm is one half inch.

What's your opinion on looks; No front spacer? 10mm front? Other? (Rember the rear's will have 30mm spacers, with ET48 wheels)

Opinions on the steering analysis?

Thanks guys.