Securing spare wheel, air compressor vs not
 

I was wondering, do X5 with air compressor have bigger spare tires?
I mean clearly there's a size difference in sizes. But why?

https://i.ibb.co/MkNz8Vw/46662d12939...tery-001-1.jpg https://i.ibb.co/PY6dLKX/Battery-001.jpg

The "army helmet" over the compressor doesn't interfere with a normal size spare. I had 245 tires I both our e53. One with air suspension one without. I can not fit my 255s in and get the floor to fit flush.

Yeah, I'm pretty sure that part only exists to clamp down the spare for cars which don't have air suspension. It has a little plastic thing that supports the trunk floor as well, but I don't think it really does anything.

Thanks guys so you're suggesting I use the smaller one then?

It supports the trunk floor...:D

It doesn't seem to make a difference if you have it there or not. The trunk floor doesnt seem to sag for me when I have left it out. Maybe I'm not putting heavy enough groceries in my trunk?

I'm going to put an amp and sub so some support would be nice. I tried putting a spare tire from E39 over the compressor cover and the inside of the tire is definitely bigger and deeper than the cover.
Noo sure how it could make cover not lay flush. Maybe a different tire design?

Bingo. It's only to prevent bending the floor if enough load is placed there. It is most certainly needed in my case.

https://uploads.tapatalk-cdn.com/202...b6bb6f6f23.jpg

You can add just a vertical tube you don't need the cute little helmet off you want to maximize space. You can also add a piece of angle iron to the bottom of the floor and have unobstructed opening in the cavity.

WOW! Andrew....do you really need THAT many tools??