Look out Boxster S, in the Spring comes BMW's second M Roadster
25 October 2005

After years of speculation and denials from BMW, the Munich firm has finally unveiled an M-badged Z4.

Since the launch of the Z4 four years ago BMW has repeatedly denied the possibility of a sportier version of the roadster, but falling Z4 sales (especially in the vital North American market) have forced BMW to improve the Z4 range’s image with this car and the forthcoming Z4 Coupé. It also provides the company with a rival to Porsche’s highly-rated Boxster S.

The car will get its first public outing in January at the Detroit Motor Show and will go in sale in the UK in the Spring. There’s no word on pricing yet, but expect it to be around the £38k to rival the Boxster S.

Visual changes over the Z4 are subtle, and the body shell is the same although there’s a chance it could look more distinctive in the metal. The car rides 10mm lower than the Z4 but is 3mm taller, with a 2mm longer wheelbase. Overall length is up by 22mm but the width and tracks stay the same. The rear bumper has a different underbody diffuser, and four tailpipes replace the standard car’s two.

BMW has chosen to use the current M3’s 3.2-litre straight-six powerplant, rather than the next M3’s 400bhp V8 as was originally predicted, making this likely to be the last six-cylinder M-car. It produces the same 340bhp at 7900rpm and 269lb ft 4900rpm as the M3, but in the lighter Z4 (1420kg) it gives a power to weight ratio of 241bhp per tonne (bettering the M3 by 23bhp) and a 0-62mph time of 5.0sec. Top speed is limited to 155mph.

The transmission is the M3’s six-speed manual, and the final drive ratio has been lowered to 3.62:1 to improve acceleration. But despite the extra power and torque and the car’s performance potential, the shell hasn’t been given any extra bracing to improve stiffness, which remains the same as the Z4’s.

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The Z4 M’s mechanicals are closely based on the M3 with the speed-sensitive M-differential that varies the locking action on the rear wheels from zero to 100 per cent. BMW has done away with the Z4’s electrically power assisted steering, replacing it with a conventional hydraulically assisted system – this should further improve on the Z4’s already decent steering - and the battery has been moved to the boot in order to improve weight distribution.

The arrival of the M Roadster coincides with tweaks to the rest of the Z4 range. The old 2.5i and 3.0i have been replaced with the more powerful 216bhp 2.5si and 265bhp 3.0si. The 3.0si hits 60mph in 5.7sec – 0.4sec faster than the 3.0i.

The si models are available with an auto ’box, with steering-wheel mounted paddle-shift controls. On the outside, there are new tail lights, redesigned bumpers amd four new colours.

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