BMW lets the M division build the car its engineers would want
BMW's latest M Roadster succeeds in two related ways: It grows some, ahem, "whiskers" on the otherwise masculinity-challenged Z4 with butch styling; and secondly, the implicit promise that the body makes is kept with honest-to-M3 muscle. More than a mere dress-up kit or sport pack, the 2006 M Roadster takes the finesse inherent in the Z4's already competent, baseline chassis and infuses it with heart-pounding performance derived from the M division's vast knowledge — with a little help from parts-bin raiding.
Cute goes bad
The M Roadster's more chiseled M-spec styling forecasts its speed and agility with a manly bravado the Z4 donor car only insinuates. Where the Z4 looks like an overreaching design student's idea of a roadster, the M Roadster's unique sculpting identifies it as the epitome of a real one.
At the front, its unique grille and aggressive fascia allow for better engine and brake cooling. Standard self-leveling xenon headlamps (with BMW's "corona" rings) light the way. More than just a fashion statement, the 18-inch M double-five-spoke alloy wheels are surrounded by serious Continental ContiSport Contact tires that are not (thankfully) heavy run-flats. Instead, in the trunk you get a compressor and a can of goo to get you to the nearest shop for tire repair/replacement. The otherwise amorphous aluminum hood features longitudinal creases that must've been painstakingly located to precisely align with the driver's sight lines.
Out back, there's an M-specific bumper ensemble with cutouts for the telltale quad-exhaust tips and a real air diffuser. The '06 M Roadster showcases new, adaptive LED taillamps (also on '06 Z4s) that light more brightly the harder the brake pedal is pushed. The overall effect of the M treatment to the exterior is supremely satisfying. Several times while driving the M Roadster, I saw lesser Z4s and my chest swelled with the satisfaction that comes from the exclusivity that all M variants offer their buyers. Riffing on the Z4's flame-surfacing (on a bar of soap) design netted a shape that looks like the car the Z4 should've been from the start.
While it's apparent from the outside the M Roadster is more dedicated and antagonistic than the Z4, there's more — a lot more — going on under its taut skin to give it a bite as serious as its bark. The M Roadster's brake system is part of the M3's Competition Package, and standard on the M5. The trick hardware reduces unsprung weight, enhances cooling and resists fading and warping when pushed to the limits this car is capable of producing. The 110-foot stop from 60 mph doesn't begin to indicate how well the brakes communicate and work, repeatedly and consistently.
The widely celebrated cast-iron "S54" DOHC inline-six engine, replete with BMW's steplessly variable valve timing, is transplanted from a current M3. It produces three fewer horsepower than in the M3 (Roadster exhaust particulars), and makes an ample 330 hp to propel our measured 3,277-pound roadster to 60 mph in 5 seconds flat. The 3.2-liter engine has a linear, almost electric quality to it so that any rev range feels as capable as any other right up to the 8,000-rpm fuel cutoff. With its low reciprocating mass, immediate throttle response, high compression ratio (11.5:1) and reedy exhaust note, there's no mistaking the M motorsport connection.
In raw terms, however, compared to the previous Z3-based 315-hp M Roadster, the new car shows only a negligible improvement in outright acceleration. The likely culprit is the Z4-based car's added weight and slightly different gearing. Depending on whose "curb weight" is referenced, the Z4 M is about 150 pounds heavier than the Z3 M. That difference cancels out the additional 15 hp for a no-sum gain. Don't worry. Nobody will ever say the car is slow. It'll convince V8-minded muscleheads and turbo four-bangers of the merits of a BMW inline six with one blast through the gears. The M Roadster still propels about 9.8 pounds with each horse, but how those extra pounds are carried around corners is a different story.
When our tests focused on handling, the script changed dramatically. Unlike the twitchy, previous M Roadster, the new one is chock full o' costly bits from the M3's suspension and driveline. The effect is, to say the least, pleasingly capable.
To accommodate the M3's burly rear differential, a new subframe was fitted to the Roadster. That differential (fitted to the M5 as well) features a variable locking mechanism that fluctuates the amount of lock-up between the two rear wheels based on their relative speeds. The more one wheel spins, the more locked together they become. While this system's wet-weather benefits are obvious, there's also a noticeable improvement in how the car behaves when driven hard out of corners at wide-open throttle. Combined with its M3-derived rack and pinion steering plus front and rear suspension, the M Roadster's at-the-limit control is sharper than an M3's (that always feels like it's on its tippy-toes), head and shoulders above its M predecessor (which comes off as dangerously edgy) and simply in a different world from the commuting-friendly Z4.
A 69.6-mph slalom speed is only a numerical indicator of how confident the M is. Regarding the car's balance, test-driver Josh Jacquot emoted after his slalom runs, "spectacular limit-balance in the slalom test's high-speed transitions," but he continued, "communicative steering and a meaty steering wheel that should be standard-issue on every sports car." Like a circular black banana, the "girthsome" leather-wrapped wheel forces a relaxed grip and supplies volumes of useful tire/surface information to the driver.
We find it exceptionally interesting that this M car features a back-to-basics hydraulic steering rack (no electric assist, no variable ratio, no over-engineered "active steering") and that the company's self-touted auto-clutch manual "SMG" paddle-shifter transmission is not even an option. An evolved version of a ZF Type H six-speed manual transmission completes the man-machine symbiotic relationship. While an SMG might represent impressive "because-we-can" technology, there's nothing rewarding in pulling a paddle for an upshift; no self-congratulations when the car executes one of a thousand perfectly matched-rev downshifts, and we've never driven a BMW SMG that was as smooth as we were from a dead stop in traffic. It seems that when BMW really wants to get it right, old school is still the best way to go. It's redeeming to witness that BMW hasn't forgotten how to "do" a proper steering system and manual transmission.
An excuse to just take a drive
Put all this trick hardware under your butt, lower the fully lined one-touch convertible top, find yourself a winding farm road or mountain pass, and you'll discover why the M Roadster commands an entry-level price $10K over a 2006 Z4 3.0si. The M Roadster inspires a gratifying three-way conversation between the driver, the car and the road that's about as perfect as it gets. Every bend becomes a really good one. Each approaching corner becomes an excuse to heel-toe downshift. Learn to trust it, and the M Roadster becomes an invisible force that carries your consciousness down the road as rapidly as you dare. If you can both afford and appreciate the differences, the M Roadster is worth the extra M-money over a Z4.
Twitchy or responsive?
Even more than the previous-generation M Roadster, the newest Z4-based performance car reveals to its driver all the mindless sloppiness that has crept into his non-rigorous commuting chores. This car feels like the Z4 the BMW engineers and test-drivers originally intended to build before the focus groups electrified the steering, softened its edges and added slop to make it less taxing to drive. The M Roadster's theme is immediacy: quick steering, instant brakes, direct throttle and caffeinated ride.
The M Roadster teaches its driver to tighten up his game. Don't downshift without a proper throttle blip. Don't glaze over in traffic and in a false emergency stand on the brake pedal unless you really mean to stop. Don't even sneeze if you're the type who sometimes uses his knee to steer while you remove the top from your café latte. Driver laziness and ham-fistedness are not only discouraged, they're punished with an immediate response from the car
and we love that. As the enthusiast arm of Edmunds.com, Inside Line has great respect for car companies with the guts to build a car for those who love to drive cars.
With all its intuitive athleticism, the M Roadster gains membership to an exclusive club of sports cars whose interview process weeds out wannabes, poseurs and cars that almost but never quite achieve the complete package.
Oftentimes, sporty cars offer great handling, but lack motivation (Mazda MX-5 Miata). Others provide ample firepower, but can't find their way around corners (any AMG product). Unlimited membership declined to both applicants. The M Roadster is granted true weapons-grade sports-car status with its masterful blend of engine, chassis and design. The whole package works in harmony. The M Roadster is so good that we'd put it in the same club, albeit in a different division, with the Porsche 911 Carrera 4, Ferrari F430 and Corvette Z06.
Respectively, each one of those cars represents the best that that configuration can be. For a sub-100-inch wheelbase, front-engine/rear-drive convertible, the 2006 BMW M Roadster is about as good as it gets. The M division turns the Z4 from a question mark into an exclamation point.
System Score: 8.0
Components: Our M Roadster came with a $2,500 premium package that includes many worthwhile features like BMW Assist, Bluetooth and memory seats. Also included in that package is an upgraded stereo system with 10 speakers, two subwoofers and Digital Signal Processing (DSP).
Performance: The upgraded stereo isn't much to look at, but the sound quality is impressive. With the top up, the cabin remains quiet enough to enjoy the audio system, and we found that turning the DSP off was best for most types of contemporary music. However, with the top down, the "Jazzclub" setting worked best because it seemed to give the music a little extra punch, like someone had jacked up all the EQ settings. Overall, the tone is a little on the bright side and some highs did squeak at high volume. Still, the bass is excellent and separation is very good.
The system seems able to deliver a good clean sound at almost any volume, and we ran out of tolerance long before this stereo ran out of volume. Even in the most demanding open-top environments, this system still delivers.
The dash-mounted controls are straightforward and easy to master, but a larger display screen would be nice.
Best Feature: Great sound quality top up or down.
Worst Feature: Smallish display screen.
Conclusion: An excellent sounding stereo that's worth the extra money. — Brian Moody
Director of Automotive Testing Dan Edmunds says:
I have a soft spot for small rear-wheel-drive roadsters. Roofless, nimble and lightweight is how I like 'em. Most of the time, however, I climb out thinking that the chassis was so much more capable than the powertrain. If only it had another 100 horsepower or so
My friend Matt must not have gotten the memo about the 2006 BMW M Roadster. "There's no substitute for an American V8," he tauntingly hollered as he rumbled up next to me at a stoplight in his WS6 Trans-Am. One green light and two gearchanges later, his black T/A was relegated to my rearview mirror. Try that in a Miata or a Z4.
And it's not just the motor that's stout. The utter lack of cowl shake on uneven surfaces gives this convertible a structural integrity feeling near that of a fixed-roof coupe. Steering and handling are spot-on, making maximum advantage of the 330 horsepower available under your right foot. The only aspect of this car that could be called a handful, literally, is its overstuffed caricature of a "motorsport" steering wheel rim.
If, like me, you wonder what it would feel like to drop another 100-plus horsepower in your trusty roadster, find yourself a copy of the 2006 BMW M Roadster and hang on, but bring your checkbook, too.
Senior Road Test Editor Josh Jacquot says:
It takes the company of BMW's M6 and Audi's RS 4 to make the M Roadster's venerable 3.2-liter straight six feel less than overwhelming. But that's exactly what happened during our time with the latest addition to the M catalog. The M6 and RS 4 just happened to be around the same day we ran numbers on the M Roadster and, in this company, I found the engine I've come to love during the last four years to be only impressive rather than staggering.
BMW's S54 engine isn't short on power (330 hp at 7,900 rpm), but it doesn't feel as lively at high rpm as the latest high-output German power plants. It also doesn't cost nearly as much and is aimed at a different market, so perhaps this isn't a fair comparison.
The Z4's chassis does, however, feel very modern. Gone is the semi-trailing arm suspension design of the Z3, replaced by a proper multilink setup that delivers far more confident at-the-limit handling. The Z4-based M-car transitioned confidently through our slalom course without any of the white-knuckle drama produced by the last-generation M Roadster.
Bottom line, this is a fast, confident and capable roadster that provides more thrills than virtually every other topless option available today. Even if its awesome engine is slightly less awesome than it used to be.
"I have had my Blue/Black M Roadster for just over two weeks. It is quick, handles extremely well and has great brakes. I find the ride to be firm but not punishing. This is a fine automobile with superb fit and finish. I have a DB9 and a Porsche 997S and I find this car more fun to drive than either of those two excellent autos." — Sal G., May 2, 2006
"Jump in open roadster style, but make sure your shoes aren't dirty so you don't get your comfy M seats dirty. I could lose my license in a few seconds in this car, 4.5 to be exact, but I would be smiling the entire short time. I haven't been able to use the entire rev range due to the break-in period, but just thinking about it gets me excited. Suggested improvements: Cupholders! These things could not be any more annoying or inconvenient. I'd rather have a car without them than have them where they are in this car. The exterior looks nice but could use a little more work. It just doesn't look sporty enough, but that's just my opinion." — Bimmer Boy, April 20, 2006
"This car is a dramatic improvement over my old Z4 (2003, 3.0i). The ride alone is worth the money, and the engine is more than powerful enough. The cornering and straight-line stability are delightful. The engine noise of the Z4 was better (piped in sound), but I have not yet been able to get to high revs due to break-in period. I love the Z4 look; it really is better in real life, and the M roadster is sharper and more aggressive-looking. Porsche Boxsters everywhere, not many of these. Get the hardtop prep option so you can go to the track. The break-in period is killing me: <5,500 revs for 1,200 miles!" — J. Shaffer, April 4, 2006