This early (2003-2004) Z4 2.5i was BMW's immediate successor to the Z3. It had fully modern underpinnings compared to the Z3, which was running around until the 2002 model year on a semi-trailing arm rear suspension cribbed from the old 1982-vintage E30 3-series. (This was done for reasons of both cost and compactness; from the rear suspension forward the Z3 was pretty much identical to the newer E36 3-series, but its wheelbase was a foot shorter.)
The Z4 had the multilink rear derived from newer 3-series cars, but as a result had a 4-inch bump in wheelbase length over its predecessor. On the upside, handling was improved and it didn't squat like a motorboat under acceleration.
The 2.5i was the cheaper engine option, featuring the 192hp M54B25 2.5 liter inline six. Buyers could also opt for the 231-horsepower 3.0i.
As a fan of the Z3's lines, I dissed the Chris Bangle-era Z4 pretty hard when it debuted, but like most of the Bangle Bimmers, the lines have aged well over time.
BMW insisted on calling it a roadster, but since the car has a permanently-affixed folding top, that's not exactly accurate. It is a sports car, though.
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