because the xi was going to be an awd that maybe you would drive it in harsher conditions than regular so they give you extra clearance to avoid i guess things such as snow banks or something. And no there are no downsides to lowering your car except the fact you may catch the occasional coke bottle or something underneath the front of your car. the suspension etc are improved greatly by the lower center of gravity and the awd drive function stays exactly the same. and before you ask yup i have a 330xi and i have lowered it with h & r springs and the car not only looks 100 times better but handles that much better too. hope that answers your question. oh i guess i can think of one downside it may null your warranty on the suspension aspect of your car unless you get a dinan suspension put in it.