They're building German hot rod roadsters in South Carolina. It's BMW's best moonshiner's brew.
Since its introduction, BMWs Z3 has served as something of a clay form. Variations on a central theme have grown every year on the Z3, this M version being the third. (A Z3 Coupe will be hatched in 1999.)
Any lukewarm reception of the Z3 1.9 with its basic four-cylinder engine is temporarily forgotten on first sight of the latest Z3 variation. The M Roadster is perhaps the easiest of the Z3 flavors to figure out. Quite simply, its the Z3 hot rod. Stuff the car full of M3 engine, brakes, and transmission, beef up the suspension, add an extra element of flair and well5.
Well, good car making is never really that simple, just like racing at Indianapolis is not just simply standing on the gas and turning left 800 times. Conceiving and making cars are an Amazon river apart. Any teenage enthusiast could have told you an M edition of the Z3 would be totally rad, but merely cobbling the pieces together would bring forth a sexy rolling specifications table that drove like a dining room table with bore, stroke and transmission ratios printed on it.
American hot-rodders discovered long ago that torque doesn't just make cars accelerate quicker, it also infinitely improves your disposition. Good for what ails you, as the ads used to claim. The M Roadster has deep reserves of it, too.
Due to its size and short wheelbase, infusing the Roadster with 240 hp and 236 lbs-ft of torque dictated significant changes to the rest of the car. Of course, none of this would have been possible without the Z3 having enough room in its snout for the corporate six-cylinder engine. The M Roadster gets the stronger of two 3 Series gearboxes (ZF's Type C). The Z3 1.9 uses one grade of rear semitrailing arm and the Z3 2.8 uses beefier ones, but the M Roadster's has to stand up to considerably higher cornering loads, torque and general abuse, and therefore gets super-beefy trailing arms. In addition, the rear suspension's crossmember is upgraded.
Revalved shocks are tighter, spring rates rise slightly, the car sits lower by one inch and antiroll bars are retuned for the package. Front suspension geometry also gets shuffled due to fatter tires, the lower degree of roll angle and all the other suspension recalibrations.
Front antiroll bar end links attach by balljoints to the strut housings instead of the control arms, as they do on M3 models. Longer bar ends maintain better angularity as the car body rolls heavily in severe cornering. It also takes body roll loading away from the arc-shaped control arm. M Roadsters use M3 variable assist steering racks.
Antiroll bar sizes work with the added grip of 17x7.5-inch front wheels wearing 225/45ZRI7 tires and huge 170-inch rear wheels shod with 245/40ZR17 tires. An asymmetric ridge around the bead area keeps tires from flying off the rim if flattened. BMW's M Mobility System uses a quick tire sealer and a pump that seals and reinflates a flat-there's no spare tire.
With the Z3 platform's frolicking nature and its generally short gearing, it needs all of that rear grip to put the engine's power to the ground. More power warrants more brakes, so binders from the M3 haul things down. Vented rotors 12.4/12.3-inches front/rear are larger than the Z3 2.8 model's 11.3-/10.7-inchers.
Upping The Ante
While Europeans get the six-throttle, 321 hp, fully VANOSed (variable valve timing) ripper engine in their M Roadsters, US-guys get the Ameri-M 3.2liter from the M3 models with 240 hp, half the VANOS (variable intake cam only) and fuller torque at low and midrange rpms.
BMW has built a large portion of its reputation on the perfection of its inline sixes; this one makes a perfect example. This double overhead cam, 24-valve inline six gives a Haagen-Dazs level of refinement and 236 lbs-ft of torque at 3800 rpm. It pulls from ridiculously low rpm and wails like Pavarotti at 6000 rpm. BMW officials point out that despite 80 fewer horsepower, our American-spec engine with its vast area under the torque curve at low and mid-rpm powers the car up to 80 mph in virtually the same time as the European-spec engine. Without a back-to-back comparison, we can't comment.
Up front, greater volumes of air flow into the engine compartment. A more aggressive air dam works to reduce lift with more forceful routing of air. The absence of fog lights allow additional air ducting. On the face of it, this nose job is slight, but creates a purposeful appearance. Engine compartment vents are split by new chrome strips and M logos. Plus, aero M-edition side mirrors (which give too little view) are perched on the doors.
Other Z3s have black painted A-pillars but the M version gains a coat of body color. And those vast rear wheels require 911 Turbo-like rear fenders, also seen on the Z3 2.8.
The trunk gains a flush finishing panel nestled above four exhaust pipes under a unique rear bumper cap. Exhaust level and quality from the new four-tip arrangement strikes a balance between reminder and bark. Despite being shorter, tighter in packaging and using a completely different exhaust system, the M Roadster's song is much the same as the Coupe's.
Inside the M Roadster is the new 3-spoke M steering wheel, another new addition for every BMW wearing the magic M plate. There is also a healthy sprinkling of chrome trim throughout the interior. BMW's South Carolina assembly plant trims all M Roadsters in two colors of contrasting leather upholstery. Extra effort shows in brightening up the Roadster's driving environment. It's not as retro as the Mercedes SLK's, but it succeeds in making the occupants feel special.
At 41.8 inches, the Roadster lacks the leg room of even the Miata (42.7 in.). Tall drivers will find legroom in short supply. Indeed, with two sizable people on board, things can get cozy.
For taller drivers, the view around sharp right corners is blocked by the rear-view mirror. But, oddly enough, this closecoupled nature adds to the ease with which you can intuitively feel the car's corners.
Even in the wet, BMW and Prototype Technology Group racer Bill Auberlen managed to give us the normal racing driver heroics at Michelin's test facility near BMW's Spartanburg, South Carolina plant. After changing seats, we found out the attainable nature of those heroics.
Given the short wheelbase, power level and wide tires, the M Roadster shrugs off impossible cornering requests fairly well. It's far from benign, however. It won't save drivers from a blatant case of lift-throttle oversteer or feeding in imprudent throttle openings at the edge of adhesion, but it does warn you, despite a whole lot of low-profile tire width. When lurid slides come, they're recoverable, too. And poor surfaces upset the rear suspension slightly.
You'll have to look elsewhere for terminal understeer at anything above a trotting pace. This is made even more important because the traction control fitted to all other BMWs will not be fitted to this one. We rarely tipped into the anti-lock under even extremely hard braking, yet positioning the car under trail braking proved fairly agreeable. One point was clear, though. The M3's more sophisticated multi-link rear suspension is not just one rung up the ladder from the D's trailing arms, it's more like three rungs up.
Intimidation has always been a hallmark of high-powered roadsters. Although the M Roadster doesn't bristle with the raw, brutish kind of power under a new Corvette's or a neo-musclecar's hood, it doesn't need to. Few people will drive other sports cars with the desire needed to dust off an M Roadster.
Revalved shocks are tighter, spring rates rise slightly, the car sits lower by one inch and antiroll bars are retuned for the package. Front suspension geometry also gets shuffled due to fatter tires, the lower degree of roll angle and all the other suspension recalibrations. 
At 41.8 inches, the Roadster lacks the leg room of even the Miata (42.7 in.). Tall drivers will find legroom in short supply. Indeed, with two sizable people on board, things can get cozy. 
You'll have to look elsewhere for terminal understeer at anything above a trotting pace. This is made even more important because the traction control fitted to all other BMWs will not be fitted to this one. We rarely tipped into the anti-lock under even extremely hard braking, yet positioning the car under trail braking proved fairly agreeable. One point was clear, though. The M3's more sophisticated multi-link rear suspension is not just one rung up the ladder from the D's trailing arms, it's more like three rungs up. 