2003 Mercedes-Benz SL500-Roadster to coupe in 16 seconds

June 20, 2002
This all sounds great but the all-electronic brakes did require a small acclimatization period. The pedal's resistance is like that of an ordinary brake pedal, thanks to hydraulics put there specifically to make the pedal feel "normal."

2003 Mercedes-Benz SL500 -Roadster to coupe in 16 seconds

When you first approach the Bonneville, you'll see why Pontiac promotes the car as an "exciting alternative to traditional luxury." The car's youthful look leans more toward sporty than luxurious. And so does its bold and exciting ride.

Recently I was among a lucky group of journalists who got a turn behind the wheel of the new 2003 SL500 Mercedes-Benz roadster. It is the fifth generation of a car that debuted in 1954 and probably was most noted for its gull-wing doors, an innovation at the time. In a similar vein, Mercedes claims the new SL500 issued some 48 years later serves up an "unparalleled dynamic driving experience."

It sounds like hype, but the car lives up to the advanced billing. The suggested list is $86,655, and the SL500 drives like a dream. Numerous advanced features include a fully retractable electric hardtop that opens and closes in 16 sec with no coaxing whatsoever from the driver. There's still 8.3 ft3 of trunk space with the two-section roof stowed away. The folded-up top even tilts up a bit in the trunk at the push of a button to give easy access to storage space.

The car is fast. The little two-seater carries a big V8 that puts out 302 hp and 339 lb-ft of torque. It accelerates to 60 mph in about 6.1 sec and tops out at 155 mph, Mercedes says. It gave every indication that it was capable of hitting this speed, though I dared not find out firsthand. (The test drive was in Arizona where jail time is mandatory for speeding tickets issued at more than 30 mph over the limit. When an automaker invites you to test drive an $86,000 vehicle, it is considered bad form to wind up in jail with the car impounded.)

One way Mercedes made the new SL fast was by keeping its weight down. Aluminum components include the front fenders, doors, trunk lid, fuel-tank partition, and hood it is said to be the largest and most complex mass-produced aluminum component ever, and is 33 lb lighter than an equivalent steel bonnet.

The SL also uses a lot of aluminum in the suspension, including all-aluminum multilink rear components and an assembly carrier for the front double-link elements. The steering mechanism is also about 13 lb lighter than its predecessor. Nevertheless, some 33% of the body shell is steel (up from 19% in the last model) for good torsional rigidity and crash safety. Among other numerous features with safety in mind are a rollover bar that flies up in just 0.3 sec in the expectation of a crash, and a side-mounted air bag that lessens the risk of hitting the side window with your head, as well as forming a barrier from shattered glass or debris.

Another first on the new SL is a brake-by-wire system that separates the brake pedal from the wheels, except via a backup system for only the front wheels. A computer checks sensors monitoring pedal travel and master-cylinder pressure. It uses this information, along with data from ABS and yaw sensors, to decide how much braking to apply to each wheel, factoring in conditions such as whether there seems to be an emergency, or whether the car is turning. Mercedes says the electronic system, among other things, reduces the tendency to lock the inside wheels when braking in turns, taking advantage of natural weight transfer during cornering. The system is also hooked up to the windshield wiper control so, in wet weather, it generates short brake pulses to wipe water off the discs and keep them dry.

The SL500's powerplant boasts a healthy 302 hp.

But the car tends to stop slightly before you expect it to in stop-and-go traffic. In highway driving, however, the only anomalies my driving companion and I could detect were occasional audible "thunks" as the calipers deployed. All in all, the biggest advantage to the system seems to come in emergencies which, thankfully, we had no occasion to experience firsthand.

The SL shares an active suspension system with its bigger cousins the S-Class sedan and CL-Class coupe. There is a hydraulic servo atop each coil spring at all four wheels that adjusts spring rate depending on riding conditions. Updated every 10 msec, these actuators reduce body roll enough to eliminate stabilizer bars on the SL chassis. Drivers can also push a button that tells the system to give the car a sportier, stiffer ride. The fast response necessary to provide these qualities comes via a special engine-driven oil pump generating 2,840 psi and an accumulator at each end of the car. One other refinement is the use of a load-cell-type sensor to factor in actual vehicle load when updating the hydraulic servos. This better counteracts body lift and pitch when the vehicle is heavily loaded, Mercedes says. It comes in to play when baggage gets removed or a passenger exits. The system notes the change and adapts the suspension qualities accordingly.

The only oversight we noticed in the car was the LCD navigation center which, with the top down, washed out completely in the intense Arizona sunlight.

A Mercedes official told an anecdote that summed up the SL. He once had a college roommate who posted a picture of an SL500 on the refrigerator. When asked about it, he said the picture helped motivate him to make his first million. My opinion: If the kid had ever actually driven an SL, he'd have the motivation for his second million because he would have wanted more than one.

Lee Teschler

About the Author

Leland Teschler

Lee Teschler served as Editor-in-Chief of Machine Design until 2014. He holds a B.S. Engineering from the University of Michigan; a B.S. Electrical Engineering from the University of Michigan; and an MBA from Cleveland State University. Prior to joining Penton, Lee worked as a Communications design engineer for the U.S. Government.

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