i want to lower my 550i.. is it a bad idea or good..
any one who has done it.. does it ride good? how low did you go? ;)
do you have to change out every thing to do it?
cost???.....

If you have the cash, take a look at the coilovers. Seems like lots of members here prefer it over the traditional shocks and springs. Talk to Michael of Acute Perf. About pricing.

As for me I really like the handling of the stock sport suspension, and with kid and wife in the back seats once in awhile so I never look into lowering it.

Do you already have the sport suspension? If so, I like the stock ride and look of the sport. Most of my cars that I have lowered in the past, I ended up regretting. I really sacrificed ride quality for looks. If you do decide to lower it, do it right with a decent set of coilovers, stay away from spring swaps.

http://www.kw-suspension.com/us/kw_streetcomfort.php

Didn't see if they make a setup for the 5er, but this is what I went with on my SRT8, which is the only car I never regretted lowering.

You didn't mention if the 550 has 19" rims, I'm guessing it does. I think the 550 looks just right from the factory.