» Get the best price on a new Mercedes-Benz The Mercedes-Benz SLR McLaren Roadster is a technical tour de force. Though it wears a Mercedes-Benz badge, the car is built by McLaren Automotive in England. A division of the same group that fields the F1 car Lewis Hamilton drives, the team's previous handiwork includes the McLaren F1 -- until the Bugatti Veyron came along, the fastest production car ever built.
Though the McLaren F1 was BMW powered, the SLR is, of course, powered by an AMG Mercedes engine. The supercharged V8 displaces 5439cc and is assembled at AMG's headquarters at Affalterbach. It is based on the same three-valve-per-cylinder powerplant that powered the 55 Series AMG models.
The powerplant features twin intercoolers (one for each bank of cylinders) and an electronically-controlled twin-screw supercharger that provides a modest 0.9 bar boost.
Peak power of 460kW is produced at 6500rpm with maximum torque of 780Nm available from 3250-5000rpm. At 1500rpm, the SLR's V8 delivers in excess of 600Nm. Over 700Nm is produced at 2000rpm. In other words -- it's got some serious mumbo.
Lubrication is via a racecar-style dry-sump system. The dry-sump configuration ensures optimum engine lubrication in all conditions and decreases the overall height of the engine. This allows the engine to be mounted lower in the car, reducing the centre of gravity.
Forged engine internals are used for maximum strength and the reciprocating masses are balanced. Like all AMG powerplants, the SLR's V8 is hand built by a single engineer and bears the craftsman's signature on an engine-mounted plaque.
The SLR's AMG Speedshift R five-speed automatic transmission offers a choice of three program settings: Manual, Comfort and Sport. When Manual is selected, there is also the option of choosing between three shift speed levels: Sport, Supersport and Race. No manual transmission is offered.
As in the case of the Mercedes-Benz SLR McLaren Coupé, the chassis of the Roadster is manufactured from carbon-fibre-reinforced plastic (CFRP). Using techniques developed in F1 and the aero industry (to manufacture parts like tail fins and control surfaces), many of the SLR's components are manufactured using patented automated series-production processes.
CFRP assemblies include front and rear-end structures, the central passenger cell, the swing-wing doors and the expansive bonnet. In fact, in terms of major chassis components, only the two engine mounting spars are made from aluminium.
Offering better rigidity and energy absorption, CFRP components weigh up to 50 per cent less than comparable steel components and as much as 30 per cent less than aluminium components, says Mercedes. Compared to the SLR Coupé, the materials and techniques used in the Roadster have undergone further advancement.
"This allowed the high-performance Roadster to retain an exceptionally high, coupé-like level of torsional stiffness that is unprecedented for a cabriolet but without any significant
increase in weight, despite [adding] the mechanism for the soft top," says the company.
Mercedes claims the SLR Roadster weighs in at 1825kg -- up from the 1768kg kerb weight quoted for the hardtop version.
Components redesigned in the changeover from Coupé to Roadster include: A-pillars; windscreen frame; the rear wings; boot lid and the signature swing-wing doors. The new doors are frameless and as on the Coupé, swing forwards and upwards through an angle of 107 degrees.
At the very front of the car, the SLR features two force absorption elements that protect the alloy engine mounting structure and the passenger cell. The conical CFRP elements are around 620mm long and weigh just 3.4kg each. In a collision, the carbon-fibre structure of the elements literally shred from front to rear, "absorbing the energy of the impact with a constant rate of deceleration" says Benz.
The SLR McLaren Roadster's passenger cell features steel and alloy reinforcing in the A-pillars and doors respectively. In a side impact, wide multi-element CFRP sill structures combine with structure seat shells to protect the occupants. Fixed rollover bars behind the seats complete the safety structure.
Passive safety equipment comprising six airbags, belt tensioners and belt force limiters match the best from Mercedes, though the car misses out on the latest PRESAFE predictive infrastructure.
The SLR's all-aluminium suspension is more racecar than production car, with double wishbones at each corner. The geometry of the lower links is arranged so that the wheels increase their negative camber when the springs compress and when cornering at speed. The set up is anti-dive (under brakes) and anti-squat when accelerating, says Mercedes.
The wishbones are forged aluminium, while the wheel carriers are cast aluminium. Combined spring/damper units at the front and rear axle and an anti-roll bar at the front round off the suspension concept. To help clean up airflow under the car, the anti-roll bar is positioned above the front axle and is controlled via rocker arms, as on an open-wheel racecar.
Mercedes has abandoned the McLaren's electrohydraulic brake concept in its newest production cars but the system prevails in the SLR. Huge Mercedes-Benz-developed eight-piston brake calipers grip ventilated carbon-fibre-reinforced ceramic discs that at the front are a massive 370mm in diameter and nearly 40mm thick.
Borne of experience in DTM touring car and GT racing, the company claims the brakes are good for 300,000km of use and stable to brake temperatures beyond 2000 degrees C! They are also 60 per cent lighter than conventional cast iron rotors.
Given the depth of technology applied to the set-up it's disappointingly flawed (see our SLR drive impressions here).
Braking is aided in high-speed situations via an automatically deployed 'airbrake.' Under heavy braking, the rear spoiler rises to an angle of 65 degrees to increase the downforce on the rear of the car. Aerodynamic drag boosts the braking effect even further, Mercedes claims.
The brake system also incorporates Brake Assist, EBD, brake drying, soft stop and hillstart functionality.
The SLR also incorporates a feature called 'Tailback Assist'. While we didn't experience the driver aid, the SLR's press kit says it can be activated using the cruise control lever when the vehicle is at a standstill or when coasting at speeds of up to 15km/h.
"The advantage of this function is that in stop-start traffic the driver only needs to use the accelerator; when the accelerator is released, the system brakes the SLR to a halt at a constant rate of deceleration. Tailback Assist can remain active up to a speed of 60km/h."
The SLR rolls on 18-inch wheels with an 19-inch 'turbine' design (as fitted to our test car) offered as an option -- at a no doubt eye watering price!
At the pointy end, the standard 245/40 Michelin rubber is mounted on 9.0-inch wide rims, while the rear gets 295/35s on 11.5-inch rollers. Tyre pressure monitoring is via individual pressure sensors that use a radio link to relay information on each tyre in the cockpit's central display.
In moving to an open design, Mercedes says its design team tweaked the Coupé's silhouette, smoothing out the transition between boot lid, roof and rear bulkhead. Otherwise the original Coupe's aggressive and unique lines have been essentially untouched in the change over.
The multi-layer soft top retracts fully but is not automatic, it requires the driver to manually release catches on the windscreen frame and lift the roof "slightly". The semi-automated process takes about 10sec, says Mercedes. It seemed longer to us. And why you're required to do anything manually in a $US542K GT has us a touch perplexed,
At least the roof is good for the SLR's full top speed -- up or down. At 207mph (332km/h) the blow wave comes free.
McLaren's website (more here) includes a video section that includes drive shots of the SLR Roadster and a video on the building of the Mercedes-Benz SLR McLaren. It's worth a look...
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