New Bovensiepen Spider is Z4M that never was

More than 400hp, an overhauled chassis and swish new look for latest Alpina spin-off

By Matt Bird / Friday, 11 September 2026 / Loading comments

It always seemed strange that BMW only ever made one fully-fledged Z4 M car across three generations. Particularly with cars like the SLK AMG and Jaguar F-Type soldiering on for so long. While the most recent M40i was pretty good (and most likeable in manual Handschalter guise), there was clearly potential left untapped in the package. Potential that Bovensiepen is only too happy to untap, now that BMW has given up on the roadster.

This is the Spider, a ‘two-seater designed without compromise for driving pleasure, combining classic sports car proportions with modern powertrain technology, contemporary crash safety and craftsmanship, entirely in the spirit of ‘Fine Driving’. Perhaps unsurprisingly given the origins of Bovensiepen, the Spider very much gives off the vibe of being a reinvented Alpina Roadster S of the '00s: not as hardcore as a full-fat M car, but with performance, dynamics and luxury upgraded significantly over the base BMW.

Style, too, if these images are anything to go by. The G29 Z4 always had the right proportions - long bonnet, short rump, low and wide - yet without the wow factor of something like the Jag. Now, thanks to Frank Stephenson, the Spider looks much more the ticket, with some aero-enhanced attitude from the spoilers and splitters, a proper stance on the forged 20s and a bit of muscle around the rear end missing from the M40i. If only BMW had tried something similar. Bovensiepen reckons that the Spider boasts a ‘sporty, elegant and timeless design’ - we wouldn’t disagree.

Power comes from the familiar and much-loved B58 turbo straight-six found in the M40i, matched up to the eight-speed auto, albeit now with intake and exhaust tweaks to liberate 435hp as well as an ‘exhilarating, sporty sound.’ That’s enough for 0-62mph in 4.2 seconds and 161mph; those who need more can get a Performance Package, which opens up the Spider to the tune of 183mph and comes with additional diff cooling to reduce thermal load. It brings extra underbody bracing as well, so expect the majority of customers to go for that.

All Spiders will get a chassis rework, though, promising ‘the kind of agility that many large sports cars can no longer deliver.’ That includes ‘newly tuned’ dampers, longer auxiliary springs on the rear axle, and better brake pads; those wheels should save some unsprung mass, with chunky Michelins - 255-section front, 295-section rear - at each corner. An optional brake upgrade - probably just the thing to with a delimit - brings four-piston front brakes and larger discs all round, 395mm at the front.

But while plenty of attention has been paid to the chassis and powertrain, this wouldn’t be a Bovensiepen without the sense of occasion turned up several notches inside. Once more, the standard Z4 was never bad in this respect, though it was never all that memorable either - no danger of that with the Spider. There’s Lavalina and Alcantara throughout, with Bovensiepen Saddlery on hand for more bespoke requests. There’s a proper build plaque, too, as befits anything BMW-shaped from Buchloe.

Colours are already set for the Spiders: of the 99 cars, 40 will be Sapphire Black, 25 Sanremo Green, Skyscraper Grey will account for 20, nine will be Thundernight (the dark purple) and just five will be Frozen Grey II. Or Bovensiepen will paint one any colour you like, for those with bottomless pockets - it’s €115,500 already, or as near as makes no difference £100k. M4 Cabriolet money, in fact, though that’s not going to appeal to the traditionalists in quite the same way.

“Ever since I was part of the BMW Z8 development team at BMW in Munich in the late 1990s, purist roadsters have fascinated me. Cars that are light, responsive and therefore a great joy to drive. They appeal to all the senses and put a smile on the driver’s face,” said Andreas Bovensiepen, one of the Bovensiepen MDs. “With the third model from Bovensiepen, we are deliberately refocusing on a distinctive exterior design.” It looks like a job well done from here - over to you…