Assuming you haven't ordered the Sport Package, your 328xi will come with
all-season 16" Bridgestone EL42 or Continental SSR runflats.  Some folks
have reported excessive noise with the EL42s so you might try to specify the
Continentals (also the Bridgestones are more expensive) for your car.

See the Tire Rack link below for more info.

http://www.tirerack.com/tires/Compare1.jsp?filterType=oe&width=205%2F&ratio=55&d
iameter=16&autoYear=2007&diameter=16&sortCode=44950&minLoad=S&ratio=55&autoMake=
BMW&autoModClar=Base+Model&minSpeedRating=H&width=205%2F&autoModel=328xi+Wagon&f
ilterType=oe&vehicleSearch=true&startIndex=0&search=true&pagelen=20&pagenum=1&pa
gemark=1&speed_rating=H&speed_rating=V&speed_rating=Z&speed_rating=W&speed_ratin
g=Y&RunFlat=All

Contrary to what the dealer may tell you, punctured run-flats may be patched
like any other tire if they aren't otherwise damaged - just make sure you
find a tire shop equipped to work on them, especially since having a tire
replaced by a dealer will be very expensive.  Also, they may be replaced (on
the same wheels) with conventional tires -  many of us who have done so
carry a repair kit and 12v air compressor.

The Z4 has had OEM run-flats since 2003 and while, IMHO, the performance
Bridgestones handle great, the ride is a bit rough - and some owners have
reported deteriorating handling after the tires are half worn.   I've been
lucky and haven't had any problems with my original Z4 run-flats or the non
run-flat replacements I mounted after 30,000 miles of good service from the
originals.

Admittedly, this is a pretty controversial topic and some owners of older
BMWs claim they won't buy a new 3 series because of the run-flats.

Tom K.

Does anybody have experiences to share with runflat tires? We ordered
a 328XI Sports wagon for the wife last week. Great car. I am jealous
at all the standard stuff she gets compared to what was optional when
I bought my 325xi 5 years ago (she even gets angel eyes, which you
only could get on the 5 series back then). They all come standard with
run flat tires (at least here in the US), which sounds great from what
the dealer told us, but I have no experience with these. There is no
spare tire, which offers quite some extra room in the cargo bay.
I don't know anybody here either that has ever had a car with run
flats.
Not that we seem to have a choice, but I am still curious to hear
about experiences from others with these.

Thanks