I found the following quote from recent BMW E60 M5 press release interesting.
"Thanks to intelligent lightweight design, the M5 has managed to retain the same weight as its predecessor, its unladen weight being 1,755 (according to DIN)."
Unfortunately, it is often hard to compare the weight of two vehicles, because of varying methodology. As I recall, the "curb" weight of the E39 M5 (without options) is 4024 lbs. The curb weight of the E55 on the Mercedes Benz USA web site is listed as 4087 lbs.
How does the weight of the E60 M5 compare to the unladen weight of the E55 (according to DIN)? ...to the weight of the 545i 6-speed? ...and to the weight of the E39 M5?
Richard