there isn't many options for lowering the x5 yet...

as i know of, there is only the h&r and eibach springs which lower the front about 1.5" or so and you use the stock dampers. if you have the air suspension in the rear, you can get the dealer to lower it via their DIS computer.

then there is a full acs suspension kit (dampers and springs). i don't know how they would handle the rear if it had air suspension (maybe lower it same as the dealer does...)

and i've heard folks talk of a bilstein coilover setup with custom rear links but have yet to see the kit itself in any vendors' website... i guess i can call up bilstein directly...