BMW M Roadster

The BMW M Roadster is the BMW M performance model of the BMW Z3 and BMW Z4 convertibles. It was produced between 1998 and 2002 and again during the 2006-2008 model years. All models were produced in the Spartanburg, South Carolina manufacturing facility, though the complete M engine was imported from Germany.

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Z3 M Roadster (1998-2002)
The BMW M Roadster was designed to be the performance version of the BMW Z3, and there were significant differences between the two variants. The body of the M Roadster had many slight differences. These included front and rear bumpers, gills, rear wings, boot and mirrors.

Under the skin many of the components were beefed up with many of them taken from the E30 M3 and E36 M3 Evo including brakes and much of the suspension. Based on the E36 platform, the Z3 Roadster was considered the E36/7 platform. The M Roadster could run a wider track under the flared wheel arches as well as wider wheels and tires to try to tame the increased power. Standard tyre sizes for the M Roadster is 225/45r17 at the front and 245/40r17 at the back. The low offset of the rear wheels allows plenty of flexibility to increase the rear tire width. A dual exhaust system fed each set of three cylinders to two dual tailpipes. This quad exhaust has since become an BMW M division signature.

Other changes included adding a limited slip differential, a different gearbox and strengthening the chassis.

The interior had a different look to the standard Z3, starting with the M-version steering wheel and including different instrumentation such as an oil temperature gauge. Finally, the car was available in M-specific colors which were not released for the regular Z3, at least in the early production years (not counting BMW's Individual program).

Early cars featured ABS as standard. Traction and stability control also became standard with the new engine. The Z3 was facelifted, but in common with other BMW M vehicles, the M Roadster's appearance was not updated.

Z4 M Roadster (2006-2008)
BMW introduced an M version of the E85 Z4 in late 2006. Called the M Roadster, it's powered by the same 3.2L, 8,000rpm, S54 inline-6 engine as the E46 series M3, delivering 330hp through a manual gearbox and a new 6-speed manual transmission. Engine management is via the Siemens MS S70 with higher processing power (64 million calculations per second) than the MS S54 (25 million CPS) in the M3. Other performance parts borrowed from the M3 include the CSL's compound (aluminum hubs, iron floating rotors) brakes and most of the M3's suspension components. Other changes include a hydraulic steering setup which provides better feel than the electric system in standard Z4 models. Weighing 3197 lb (1450 kg), the M Roadster has been tested by major U.S. car magazines to accelerate from Zero-60 mph in 4.7 seconds, which is slightly quicker than the Porsche Boxster S and Porsche Cayman S. . Top speed is electronically limited to 155 mph (249 km/h).

A new six-speed manual transmission is used since the M3's original six-speed doesn't fit the Z4's chassis. The six speed is the only transmission available in the M Coupe/Roadster; its final gear ratios are virtually the same as those of the M3. It is widely reported on owner forums that the 6-speed gearbox in the 2006 & 2007 M roadsters and coupes is prone to grinding when shifting from 1st to 2nd gear at high rpm. According to reports, there has been mixed response by BMW dealerships to this issue, some owners claiming to have received entirely-new gearboxes and others claiming their dealer calls the grinding "normal".

The M Roadster's MSRP is $52,100. A fixed-roof version (the M Coupe) is also available, though marginally heavier. Around the Top Gear test track, the BMW set a time of 1:26.0 which is 0.8 of a second faster than the Base Corvette C6 LS2.

Options included a premium package (cruise control, power memory seats, upgraded audio, BMW Assist system), heated seats, extended leather, navigation and a body color aluminum hardtop.