Let me introduce you to this striking blue 2006 BMW Z4 M Roadster. It belongs to Philip, a friendly fellow who is trying to convince me that the Z4 M Roadster is undervalued in the M-car hierarchy. I’ve got a morning with the car, so let’s see if I agree.
My drive of the Z4 M droptop begins with an alfresco meander through the maze-like Berkeley Hills. Here, the roads are narrow, frequently requiring cooperation to squeeze past oncoming traffic. In this claustrophobic neighborhood, I’m happy that the Z4 M is such a tightly wrapped car. Even by 2000s standards, the Roadster has a small footprint, which lets me slip through hairpins and past parked cars.
Although the inclines here are as steep as San Francisco’s, the Z4 M makes my climb easy. Its 3.2L I6 engine—known as the S54 to BMW nerds—has good low-end torque, and the brakes’ hill-start assistance makes for anxiety-free restarts.
I admit there is a learning curve to the clutch as its engagement is soft and vague. The legwork is easy as its resistance is light, but it takes me a while to figure out where the friction plate bites.
The only discomfort on the climb through the neighborhoods comes from the suspension. When Philip bought the Z4 M Roadster for $25k in 2022, it had just 43k miles on the clock. Nevertheless, he immediately prepped it for autocrossing, installing Bilstein B8 Sport dampers, Eibach performance lowering springs, and SPL rear camber arms. These add-ons increased the Z4 M’s agility and roll resistance at the expense of a harder ride. Here in the Hills, the car jolts over rough roads. I feel the potholes’ thumps harder from the rear wheels than from the fronts because I’m sitting closer to the rear axle!
After five minutes of wiggles and squiggles, I pop out of the neighborhood and onto Grizzly Peak Boulevard. Grizzly Peak Boulevard is a connector across the local hilltop communities, and it is wide and well-paved. Now the Z4 M’s hardened suspension starts to make sense.
As I steer the Z4 M Roadster through hairpins and twists, I can’t feel an iota of slop in the car’s handling. Thanks to the updated suspension hardware, my wrist-flick commands are instantaneously enacted at the front axle. The front tires feel Velcroed to the pavement, and there is little to no lean as we dance through the corners. The rear end follows the front faithfully, with both axles working in harmony.
As with all modern M cars, the Z4 M Roadster is fitted with a fat-gripped sports steering wheel. The wheel is as girthy as a tennis racket handle and wrapped in squishy leather. It feels familiar in my hands, as my E90 M3 had a similar setup.
Thankfully, when BMW M-ified the Z4, it tossed out the convertible’s electronically-assisted steering system and fit the E46 M3’s hydraulically-assisted steering rack in its place. The M rack gives the Z4 M lovely steering pacing—it’s moderately quick—and hefty weighting. I love that the system also clearly communicates road surface textures.
We stop on the ridgeline to take photos of the Z4 M. The Z4 was one of the early Bangle flame-surfaced designs, which were controversial at the time. Many shoppers, including myself, thought the pre-Bangle cars were more elegant and beautiful.
As my eyes explore the Z4 M Roadster, I find it striking but no visual match for the same-year M3. (The E46 M3 is an undisputed beauty.) My favorite Z4 design elements include the Zoro-like “Z” slashed into the front fenders—the Z is punctuated with a roundel—and the car’s long hood/short deck proportions. Like an AMG GT or S2000, the seats are pushed back over the rear axle, but unlike those other cars, the Z4 M is not a front-mid-engine car, as its I6 crosses the front axle.
Considering the pizzazz put into the exterior styling, the Z4 M’s interior is rather staid. In front of the steering wheel are twin pods for the tachometer and speedometer, and a cluster of warning lights between them. To the right is a tiny fold-up navigation screen, with software that predates iDrive. A row of preset buttons and radio controls accompanies the CD player; below it are the three HVAC knobs and the buttons for the convertible top, seat heating, and stability control. Finally, next to the shifter is the sport button for the aggressive throttle mapping that makes the engine feel peppier.
The Z4 M’s cabin is tight without being restrictive—call it cozy if you like! Part of the trunk has been consumed by the convertible’s motor, but there’s enough room leftover for a pair of carry-on suitcases and a backpack. I could easily imagine taking my wife on a romantic weekend getaway in the Z4 M Roadster.
After a few minutes of camera clicking, repositioning, and clicking some more, I wrap up my photo session. Then it is back down Grizzly Peak for more driving thrills!
I’m driving with the top down, and the open-air calm of the Z4 M Roadster’s cabin is impressive. A plate of glass between the rollover hoops keeps the wind from curling back into the cabin. The air blocker works well, and I feel insulated from wind buffeting, so long as the side windows are up. The top of my hat does rustle in the rapid flow over my head, but shorter drivers may avoid the scalp tickle.
I take the Z4 M down the curiously-named Fish Ranch Road. Fish Ranch Road is too straight and trafficked to be fun, but it is wildly undulating. I’m nervous that the low-slung Z4 M will scrape on the pronounced dips, but it does not. At my modest pace, the firm-kneed Roadster seems to ride on top of the bumps, rather than letting the suspension breathe through them.
If the road’s wild asymmetric camber changes are tugging at the front tires, I can’t feel it in the steering. The Z4 M tracks straight and true, without kickback or tramlining. Resistance to camber chasing is one benefit of the modest-width front tires. The Roadster is on its factory 18” wheels with Continental ExtremeContact Sport O2 rubber, 225/45 front and 255/40 rear.
A short hop on the highway offers me an opportunity to rev the 330 hp S54 engine to its 8k rpm redline. At lower rpm, the engine is quite melodious with a nice deep growl, but the soundtrack gets gruffer near redline. The torque is even as the tachometer needle winds right, with just the slightest crescendoing surge past 7k rpm. As someone who still pines for the E90 M3’s S65 V8 and its 8.3k rpm shriek, I find myself wishing for more top-end drama from the Z4 M. The S54 I6 is a phenomenal engine, but BMW has built crazier mills!
On the highway, I try top gear to see how the car cruises. Sixth drops the revs to ~2k rpm at 70 mph, and the frenetic vibrations that filled the cabin seconds before melt away. Now the Z4 M is calm and comfortable. The plush sports seats expertly support my back, torso, and thighs. I’m ready for long miles in the Roadster.
The next roads I planned for the morning are well-suited to the Z4 M’s drivetrain but poor fits for its suspension.
Bear Creek Road has long straightaways and rolling sweepers, which are eaten up by the engine’s broad rev range and the transmission’s long gearing. When I step on the gas at 4k rpm, the S54’s individual throttle bodies respond with split-second urgency. I appreciate the paper-cut precision of the Z4 M’s throttle—I can fine-tune my acceleration with minuscule adjustments.
The Z4 M Roadster tips the scales at 3300 lbs, giving it a power-to-weight ratio of 10 lbs/hp. That number can’t hold a candle to today’s M cars: the 2025 M4 Competition, for example, punches out 6.7 lbs/hp! Back in 2006, Car and Driver squeezed a 4.6s 0-60 mph run and 13.2s quarter-mile time out of the Z4 M Roadster. The same magazine clocked a stick-shift 2021 M4 at 3.8s and 12.0s. These days, the Z4 M Roadster isn’t top-tier fast, but it still puts numbers on the speedometer that could get me into big trouble!
The Roadster’s second gear reaches 70 mph and its third to nearly 100 mph, so my canyon carving is a two-gear affair. That’s too bad, because the Z4 M’s short-throw ZF manual has the best shift feel of any BMW box I’ve driven! The stick is stout and tight, and the positive snatch through neutral tells me exactly when I’m leaving one gear and on my way to the next.
Oh, if only I were on a race track, then I’d be in heaven! It’s a joy to wring out each and every rev and feel the Z4 M hunker down through the corners.
Unfortunately, Bear Creek Boulevard is lumpy, and the front shocks bang over the bumps at speed. Each hit rattles the car’s hood; I find myself wincing and apologizing after the impacts.
My last planned road is in even worse repair, as its sagging tarmac is sliding into a creek! I alternate between marveling at the Z4 M’s proficiency at slicing through the second gear corners—the car is pointy, yet surefooted—and wincing at the abusive banging from the front end. All the hand-me-down E46 M3 hardware—engine, suspension, steering and brakes—works like a charm on the Z4 M. The aftermarket suspension, on the other hand, pines for smoother surfaces.
(On account of the heavy steering, measured steering pace, and front-engine layout, the Z4 M doesn’t pirouette into corners as quickly as a mid-engine Porsche Cayman, but it’s not far off.)
Even though the Z4 M Coupe is said to have twice the torsional rigidity, the Z4 M Roadster doesn’t feel compromised by going topless. Some convertibles are messes of quivers on rippling pavement, but the Z4 M Roadster is largely shake-free. Only the slightest shimmying can be felt as the road tries to twist the chassis.
The only fly in the Z4 M’s dynamic ointment is the brakes. They have a soggy pedal that undermines my confidence, even though the pads and fluid are resisting fade. Would new pads, lines, or fluid make the middle pedal as tight as the steering? It’s a question worth investigating.
After driving the last mile of twists, I stop to raise the Z4 M Roadster’s lid. The soft top is electrically actuated, and—in less than a stoplight’s cycle—I’m driving in the shade. The penalty I pay for UV protection is greatly diminished visibility: the top creates massive over-the-shoulder blind spots.
It’s a short highway hop back to my waiting AMG GT S and the end of my test drive. At 70 mph with the top up, modest amounts of wind noise and road roar seep in. Nevertheless, the din doesn’t strain civilized conversation with my copilot. The Z4 M is a comfortable highway car.
What would I change about this Z4 M Roadster? Well, I’d like the suspension to be more tolerant of bumpy back roads and the engine to have even more maniacal top-end zing. A better aural connection with the engine would be lovely, too. Perhaps a carbon air box or aftermarket exhaust would turn up the volume?
Finally, I have a driver-specific niggle: I drive the canyons at a seven-tenths pace, and if I want to wag the rear tires, I need monster torque or milquetoast tires. The Continental ExtremeContact Sport O2s have grip that bests the S54’s grunt, so I’d consider making the Z4 M more frisky by putting it on less aggressive tires.
And is the Z4 M Roadster an underappreciated value? Well, it has all of the traits I love about M cars, including a ringer of an engine, feelsome steering, precise handling, exceptional seats, and a Jekyll-and-Hyde personality. (It can cruise calmly or ravish a race track.) For $25k, that breadth of ability and fun is an absolute bargain!
Mike's Steering Column 