i have a 2008 e70 3.0 and it comes with the stock 18" runflats 5 stars..... i wanted to upgrade to the 21" 128 wheels however on the bmw catalogue it states that there only in combination with the self leveling suspension.... whats that about? i dont think i have the self leveling suspension ..... i guess that means i cannot install them?? any advice? knowledge? thank you.