Hi Guys: I recently bought a new 2001 E39. It also had a rumbling noise which I figured out was bad cupping on the tires due to bad struts. It sounded like I was going over rumble strips found on the shoulder of the road.
Anyway, I found all this out after I replaced the bearings. You will need a very powerful impact wrench and the proper air pressure to remove these bolts. the lock tight that the factory used actually begins to bind as you remove the bolts. I once I got them backed out a little, I used a little pb blaster and then worked them in and out with the impact wrench until they eventually came out. I took lots of pictures of the process and replaced the struts, bearings, pads and rotors all at the same time. All very easy.