After yesterday's hardtop roof reveal on the a new BMW Z4 Roadster, here are the latest spy photos of a silver prototype with the return of more psychedelic camouflage but still with an exposed folding hard top.

After yesterday's hardtop roof reveal on the a new BMW Z4 Roadster, here are the latest spy photos of a silver prototype with the return of more psychedelic camouflage but still with an exposed folding hard top.

Following in the footsteps of the 3-Series convertible, plus its Mercedes SLK rival, with a retractable folding steel top, these dynamic pictures at the Nurburgring Nordschleife show better than ever before, a more muscular presence.

BMW isn’t content with stealing customers away from the SLK as it also takes aims at the Porsche Boxster with BMW's new range of powerful engines particularly the twin-turbocharged 3.0-liter straight six-cylinder unit and possibly the 4.0-liter V8 from the M3 for the top of the range M model.

Our sources state the Z4 is expected to debut at Detroit this January. However other reports are saying a production ready concept will appear in Los Angeles next month. Either way, production will begin by spring in Germany.

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Dynamic Spy Shots of BMW Z4 on the Ring