Since I don't know what rims or tires you have---width of spacers you will like change with width of rims and even what tires are on the vehicle.

To be sure spacers are not so wide your tires will throw stuff on the side of your X measure from the widest point of the tire to the inner lip of the fender. At that spacer width the exposure of the tire at the bottom of the fender will be outside the fender but not enough to be a problem

Spacers should be from quality provider like ECS tuning or Velocity motorcars so you can be sure they are true.

Any spacer you use should be secured to the hub and lug bolts should install in the original holes.

Spacers require longer lug bolts that offset the width of the spacer.

Unless you are not concerned with handling, spacers should be the same width front and rear. Wider spacers in the rear will increase understeer.

Spacers change alignment. Regardless of the width the alignment should checked

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas