Used 2006 BMW M Convertible

The combination of a powerful engine and a little car never gets old. The new 2006 BMW M is a solid choice for a sports car in the $50,000 range.

As the BMW Z4 enters its fourth year of production (the automotive equivalent of middle age) the company gives the lineup a shot in the arm with the injection of the M treatment. As enthusiasts know, BMW's in-house tuning firm goes by the letter M (for motorsport), and whenever its engineers lay their talented hands on a vehicle, good things happen.

The 2006 BMW M features much of the same go-fast hardware used in the M3 coupe. We're talking everything, from the engine, steering system and brakes to the variable differential lock and a handful of suspension parts. The M (which includes the Roadster and new-for-'06 Coupe body styles) also has unique 18-inch wheels and bodywork, not to mention about 200 fewer pounds to carry around compared to the M3.

Naturally, the M's status as a BMW is pretty much a guarantee of a high fun-to-drive quotient. A ripping 330-horse inline six coupled to a sweet-shifting six-speed manual makes straight-line acceleration a blast, literally speaking, while a taut chassis and telepathic steering make slicing through the curves in the road just as enjoyable. BMW enthusiasts will likely recall that this same engine was also featured in the previous, Z3-based M Coupe and Roadster. Though its horsepower ratings are pretty similar to the previous generation's, the new M's more sophisticated suspension and roomier interior make it a better package overall.

In the niche market of high-powered roadsters and coupes, the 2006 BMW M's arrival has made the final purchasing decision that much harder. The Mercedes-Benz SLK55 offers the security and comfort of a retractable hardtop but no manual transmission and a higher price tag. The Porsche Boxster S and Cayman S offer much more handsome styling (unanimous opinion among our staff) and a bit more athleticism, but less performance in a straight line. And while a Corvette will give you 400 horsepower and more performance than you'll ever need for less money as well, it lacks the panache of the German trio. In other words, there's not a loser in the bunch, and we suggest buyers choose based on their own particular set of desires.

The 2006 BMW M is a performance version of the Z4 and is offered as both a convertible and a coupe. Special styling details, such as a more aggressive front fascia with larger air inlets, a pair of ridges in the hood and a set of quad exhaust outlets flanking a rear diffuser separate the M from its less potent Z4 brethren. Since the M is at the top of BMW's line, virtually everything that's optional on a Z4 is standard. Standard fitments include xenon HID headlights, leather sport seats, auto-dimming mirrors and power seats (with driver's memory). A sport suspension with firmer calibrations and 18-inch double-spoke wheels shod with 225/45 front and 255/40 rear performance rubber is likewise included with all Ms. A navigation system is one of the few options.

The M's 3.2-liter straight six is identical to the M3's, save for a slightly more restrictive exhaust that shaves off 3 horsepower, leaving it with an official rating of 330 hp at 7,900 rpm. Torque remains the same at 262 pound-feet at 4,900 rpm. A six-speed manual gearbox is the sole transmission offering and a variable differential lock helps put the power to the pavement. BMW claims a 0-60-mph time of 4.9 seconds and EPA fuel economy estimates are 16 mpg city, 24 mpg highway.

The M comes with four-wheel antilock disc brakes, a stability control system, rollover protection, side airbags, active knee protection and child-seat anchor points for the passenger seat. In NHTSA crash tests, the virtually identical BMW Z4 earned four out of five stars in frontal-impact crash tests along with a three-star rating for side-impact safety.

Although the M shares its steering system, brakes and numerous suspension parts with the M3, most of the parts were tuned specifically for it. The ride quality is noticeably better than the M3 on the street. In fact, although the M is remarkably stiff for a convertible, you seldom get any harsh impacts. Steering feel is about perfect and the brakes are way more than you'll ever need for the street. As stiff and precise as the M is at normal speeds, rip through a corner fast enough and the car does exhibit some body roll. Nothing off-putting, just enough to let you know when you're approaching the M's considerable limits.

The cockpit features a pair of aggressively bolstered sport seats, a chubby M edition steering wheel and a Motorsport spec tachometer with a variable redline that settles at 8,000 rpm when the oil is fully warmed up. The speedometer reads to 180 mph, but the computer will cut you off at 155 mph. Although you sit deep in the cockpit, the view over the arched dash is still good. There's enough legroom for 6-footers but the cockpit feels tight even for smaller folk. There's a new trim option BMW calls "Carbon Leather," which is black leather with a carbon-fiber pattern. Everything else is similar to the Z4 in design and feel except for the automatic climate-control knobs, which get extra rubber trim around the edges. With the roadster's top up, the trunk has a capacity of 9 cubic feet, 1 cube less than a Benz SLK. Fortunately, folding the top down does little to diminish the M Roadster's capacity, whereas stowing the hardtop steals much of the SLK's capacity.