Right from the word go the target was ambitious: the aim was for the new Mercedes-Benz SL to tip the scales weighing five percent less than the previous model. Already declared the benchmark, the predecessor itself was a shining example boasting various lightweight design measures, even including bonnets made of aluminium.
At the same time, the specifications book prescribed more comfort, more output coupled with considerably reduced consumption and fewer emissions, plus a more rigid bodyshell and even more safety. These demands would render the vehicle heavier and not lighter – that was clear. The experts calculated a weight increase of at least 75 kilograms.
Only a lightweight construction on a totally new level – which included all the vehicle components in the equation – could reconcile these contradictory requirements. In actual fact, the developers at Mercedes-Benz have succeeded in undercutting the ambitious weight targets. The new SL 500 weighs no less than 125 kilograms less than the predecessor of the same name. This corresponds to a reduction of 6.5 percent. Meanwhile the SL 350 even manages to exceed the high expectations even further – with its weight saving of 140 kilograms – equating to 7.7-percent less.
Here is an extract from the long list of lightweight design measures:
Bodyshell.Converting the entire bodyshell to aluminium cuts its weight by 24 percent in contrast with a steel bodyshell featuring comparable properties (a weight saving of 110 kg). Even the upper door hinges consist of aluminium.
Damping.The switch from absorber foams to sprayable acoustic compositions with variable layer thicknesses which can be shaped according to requirements, plus modified underbody panelling, results in weight savings in the order of 2.5 kg.
The guide rails for the window lift mechanisms are now comprised of aluminium instead of steel, amounting to a weight saving of 0.5 kg.
Vario-roof in magnesium/plastic design.The front part of the roof and the C-pillar are produced in magnesium/plastic, plus there are additional optimisation measures regarding the design of the tubular frame, rear shelf, rear window frame and roof frame. The weight reduction amounts to 15 kg.
Glazing.The windscreen is 0.5 millimetres thinner, with an acoustic film. The weight reduction amounts to over 1 kg.
The rear windscreen is 0.7 millimetres thinner, resulting in approximately 1 kg less weight.
Interior.The dashboard mount consists of a continuous IHP aluminium tube with magnesium struts and moulded-on polymer brackets. The weight reduction is 2.2 kg.
With the introduction of shift-by-wire technology, the large shift lever has been replaced by a joystick-like lever. This DIRECT SELECT gearshift system weighs only one sixth as much as the automatic selector lever used in the preceding model. The weight saving is 1.4 kg.
The boot floor is in the form of a polyurethane honeycomb plate instead of the wood plate previously used. The passenger’s foot plate has been switched over to plastic from steel, saving 1.5 kg in weight.
Seat.New seat structure with new adjustment motors, but a standard-fit 4-way lumbar support and crash-responsive head restraint. Weight savings: 11 kg.
Electrics.Thanks to an intelligent dynamic load management system, two batteries are no longer necessary; one 95 Ah battery in the boot is sufficient, supported by a 12 Ah battery for the ECO start/stop function. Weight savings: approx. 4 kg.
Every vehicle is given a customer-specific wiring harness for the interior, cockpit and engine compartment. Thanks to this tailor-made cable harness, additional weight in the form of wires which are surplus to requirements can be saved – to the tune of up to 0.4 kg.
The innovative Frontbass system avoids the need for a separate woofer and door loudspeaker. Weight reduction: over 4 kg.
Axles.The four-link front axle had already undergone extensive weight optimisation for the preceding model, featuring steering knuckles and spring links made of aluminium. The two front-axle halves now consist entirely of this material. The integral support frame for the front-axle halves, steering gear and engine is also produced in aluminium. Total weight savings: 11 kg.
The rear-axle subframe consists of high-strength steel with adapted panel thicknesses. It has been optimised in accordance with the specific engine line-up for the SL 350, resulting in a weight reduction of 2.6 kg over the SL 500.
Suspension, Damping.The standard-specification semi-active adjustable damping in the SL 350 is lighter than the standard suspension system, saving 10 kg in weight.
Brakes and pedals.Optimised brake cooling eliminates the need for large and thus heavy brake discs on the front axle. Weight savings: 3.8 kg.
Lightweight wheels.New standard-fit lightweight wheels for the SL 500 are around 15 percent lighter than cast wheels. Weight saving: approx. 4 kg
Wheel bolts with a weight-optimised head. Weight saving: approx. ¼ kg.
Source: Daimler AG