2011 BMW Z4 sDrive35is Road Test

Not an "M," Maybe Not Even an "is"

Published: 09/23/2010  - by Erin Riches, Deputy Editor

We've broken our own rule, and we're driving south on California's Highway 1 in the 2011 BMW Z4 sDrive35is. If you really want to drive, this isn't your road. Too many cars, too few passing zones and too much slow add up to too little fun.

But on this last Sunday of summer, we've pointed the fastest member of the 2011 BMW Z4 family toward Big Sur. The sun will be down in an hour, and soon enough we'll pass this 18-wheeler, then the beige Prius, and then we'll reel in a dawdling 3 Series sedan two miles down the road.

Finally, it's dark and the cold salt spray of the Pacific is pelting our arms, but we have the road to ourselves. We gather speed. And between the N54 engine's turbos and the dual-clutch transmission's quick gearchanges, it's so seamless that it feels like we've been going this fast forever. The distinctive — and by distinctive, we mean loud — Z4 sDrive35is exhaust note goes on in a never-ending grunt echoing off the cliffs. The convertible's adaptive bi-xenon headlights light up the whole coastline. We see our way through the exit of every turn before we've even entered.

For these 20 minutes, we reclaim Highway 1 for driving and we do it from the leather-lined cockpit of the 2011 BMW Z4 sDrive35is.

The Convenient Performance Car
Soon, we stop for fuel in Cambria, and in all of 18 seconds, our top-down drive comes to an end as we take refuge under the vacuum-sealed snugness of the Z4's retractable hardtop. Before long, we don't even remember that we're driving a convertible.

It takes us longer than 18 seconds to work the car's manual seat adjustments (yes, we're apparently dumber than your average Bavarian), but we'll spend the next five hours in this driver seat and never once feel kinked up.

Such comforts are a big part of the sDrive35is Z4's appeal, even though BMW is keen to market the convertible's performance credentials.

In the 2011 BMW Z4 sDrive35is, the automaker has cranked the boost to 11.6 psi (up from 8.7 psi) on the twin-turbocharged and direct-injected 3.0-liter inline six-cylinder, while improving the engine's breathing. The result is 335 horsepower at 5,900 rpm and 332 pound-feet of torque at 1,500 rpm (with an additional 37 lb-ft wallop available during a short-lived 14.5-psi overboost) — up from 300 hp and 300 lb-ft on the standard Z4 sDrive35i model.

It's impossible not to notice the car's profound quickness, but as with other versions of the N54 engine, you're reveling over a torque band that never seems to end, rather than riding it out to a big high-rpm rush like with the normally aspirated 3.2-liter inline-6 in the discontinued Z4 M and the beloved E46 M3.

BMW's seven-speed automated manual transmission is new to the 2011 Z4 line. It's known alluringly as the DCT, which is basically the same dual-clutch gearbox as on the current M3, albeit with three shift modes instead of 11. It's a $1,575 option on the standard Z4 sDrive35i if you don't want the conventional six-speed manual (lesser Z4 sDrive30i models still take either the six-speed manual or a six-speed automatic). However, the top-of-the-line Z4 sDrive35is comes only with the DCT.

The other "is" in BMW's lineup, the 335is coupe, is offered with both the dual-clutch unit and a conventional six-speed manual transmission. BMW says this is because the Z4 35is is also on sale in Europe where its customers like the high-tech dual-clutch. The company believes that the North America-only 335is would appeal to the small group of Americans still attached to the manual transmission. That must surely be some sort of first.

Either way, shift quality of the Z4's DCT is smoother than that of the V8-equipped M3, so there's a strong temptation to put it in "D" and forget about it, which is exactly what we do for the rest of our drive.

But Those 19s Are Gorgeous
There's plenty of freshly poured blacktop on a tourist route like Highway 1, so we don't give much thought to the 2011 BMW Z4 sDrive35is' ride quality. Once we're back on Southern California freeways, though, it's top of mind. The Z4 sDrive35is wears standard 19-inch wheels and 225/35R19 front and 255/30R19 rear Bridgestone Potenza RE050A run-flat summer tires. Our butts have filed a restraining order against these tires.

It has been documented that the Inside Line editors are wimps. And with this lower-profile rubber, the Z4 35is should grip better and handle better than the 2009 Z4 35i with 18s (225/40R18 front, 255/35R18 rear), and all will be forgiven, right? Sorry, no.

Apart from the tires, the suspensions on these two cars are pretty much identical. Our 2011 Z4 35is comes standard with the M suspension, which specifies adaptive dampers (and driver-selectable Normal, Sport and Sport+ modes) and a 0.4-inch-lower ride height. Our 2009 Z4 tester had this setup as an option.

Yet the Z4 sDrive35is is much slower than the 2009 Z4 through the slalom. Its 66.7-mph performance — versus the 2009 Z4's 68.9 mph — is closer to what we'd expect from a front-wheel-drive family sedan than a rear-drive sports car.

Blame goes to those very short, very stiff sidewalls, which don't have enough compliance to stay glued over bumps and ripples. There's a small dip at the third cone in our slalom that sends the car skittering sideways and makes our test-driver late for the next cone. The more aggressive damper maps in Sport and Sport+ modes only make the car more nervous, something we also notice when picking up the pace on local back roads.

Through it all, our tester's steering stands mute. BMW hasn't changed the steering ratio on the sDrive35is model, but the electric power steering assist map has been updated. The result is a leaden heft to the wheel in Sport and Sport+, but nothing you would describe as steering feel.

If this was a full-on M car, we'd expect BMW would have retuned the springs and dampers to make them work better with the 19-inch wheel/tire package, likely dumping the run-flat rubber in the process. The Motorsport-division engineers probably would have reverted to conventional hydraulic power steering assist, as they did on the earlier Z4 M.

Braking, at least, is unaffected by the 19-inch-tire package. Our 2011 Z4 has the same braking hardware as the 2009 Z4, and it stops from 60 mph in 106 feet — versus 105 feet for the earlier car. Skid pad performance is slightly better on the 2011 Z4 (0.90g versus 0.87g).

A Smidge More Speed
If there's anything to justify the 2011 BMW Z4 sDrive35is' $61,925 base price — more than $9,000 above the base price of the standard sDrive35i model — it's the extra speed.

Launch control is included with the M DCT, but as on the M3, it's a "watch this" novelty rather than a legitimate go-faster tool. It's neat to see and hear the car do its thing, ripping off flawless redline upshifts while you have the throttle pinned to the floor, but the program allows too much wheelspin — and disengages as soon as it detects you "pedaling" to compensate.

The quickest launch involves selecting Sport+ (which hastens throttle response), sliding the shifter over to the "DS" mode and leaving the traction control on. Our 2011 Z4 sDrive35is arrives at 60 mph in 5 seconds flat (4.5 seconds with rollout like on a drag strip). Alas, this isn't much quicker than the manual-shift 2009 Z4 sDrive 35i, which ran a 5.2-second 0-60 time (4.9 seconds with rollout).

However, the gap widens by the quarter-mile, as the Z4 sDrive35is makes a 13.1-second pass at 107.5 mph. This trap speed qualifies as blistering, and indeed it's the highest trap speed we've ever recorded in a car with the N54 engine. The 2009 Z4 went through at 13.4 seconds at 103.7 mph. Top speed is limited to 155 mph in the 2011 Z4 sDrive35is, just as on all Sport package Z4s.

Not Really an "is"
You'll pay handsomely for that straight-line superiority. For $64,225, our 2011 BMW Z4 sDrive35is tester has keyless start, a USB input and heated seats, but no Bluetooth or navigation. However, you can easily option up a standard 2011 Z4 sDrive35i past the $60,000 mark, and indeed our 2009 Z4 crested $64,000.

But here's an ugly truth: The 2011 BMW Z4 sDrive35is is less car for the money.

Maybe you won't slalom your Z4 sDrive35is, but you'll probably take it on a back road. And you'll find you can only lean on it up to a point. The composure isn't there, and it feels like there are a million things happening behind the scenes that the car isn't telling you about.

On Highway 1, it's the superb headlight coverage, not the steering feel, that gives us confidence to press harder in the Z4 sDrive35is. This might be OK in a 7 Series, but in the performance model of the Z4 line, we want more than technology. We want a conversation.

The manufacturer provided Edmunds this vehicle for the purposes of this evaluation.