MERCEDES-BENZ has joined the ranks of car-makers redefining the meaning of the word ‘coupe’.

Not since the luxury Rover P5B four-door coupe of the 1960s has the car industry challenged public perceptions of what the word actually stands for – which in most people’s mind is traditionally a two-door vehicle wrapped in a low-slung sportscar body.

However, Mazda did it several years ago with the four-door, four-seater RX-8 sportscar, and now it is Benz’s turn with its new CLS four-door coupe.

And, like the RX-8, cashed-up CLS customers are clearly unconcerned about nomenclature, as almost half of this year’s allocation of 400 CLS coupes has been sold.

The CLS is based on the Vision CLS, unveiled to an approving audience at the 2003 Frankfurt motor show, and uses E-class platform architecture.

German media described it as the "car to tempt the family man", and not surprisingly most buyers in Australia are expected to be professional males and between 45 and 55.

As a car, it is a four-seater with plenty of legroom and tight headroom but espousing definite coupe pretensions.

It is low-slung, aggressively styled, with the CLS 500 and CLS 55 AMG boasting fat 18-inch alloys and the practicality and boot space of a conventional sedan. Even with a full-size spare it has a roomy boot.

Interestingly, too, Mercedes-Benz Car Group managing director Horst von Sanden said about 40 per cent of CLS buyers will be new to the three-pointed star.

"Our market analysis indicates clearly that customers who have previously shown little or no affinity with the Mercedes brand will see the CLS as an attractive prospective purchase," he said.

He admitted it had strong technical ties with the E-class but did not believe the CLS’s arrival would dilute the brand.

"It’s very definitely a different car and one of the most striking models in the Mercedes line-up," he said.

A small number of buyers were expected to opt out of the E-class for the CLS but Mr von Sanden said he did not expect any substitution from the S-class range.

"For many existing Mercedes owners the CLS provides an opportunity to stay with the three-pointed star when moving up from, say, a coupe like the CLK or sedan like the E-class into this new segment," he said.

He insisted that most sales would also be incremental on top of the 2200 E-class sales expected this year. Many customers are expected to cross-shop from a Porsche 911, Maserati Quattroporte and BMW 6 Series. The CLS also had the potential to attract Jaguar and Audi customers, according to Mr von Sanden.

Even though the CLS carries a $16,000 premium above equivalent E-class models, and the CLS 55 AMG is $22,300 above an E55 AMG, Mercedes-Benz Australia has already sold 190 with 40 customers opting for AMGs.

All up, Mercedes will deliver 400 CLS coupes this year.

Initially, two models will be available – the 225kW/460Nm 5.0-litre V8 CLS 500 at $173,900 and the flagship high-performance 350kW/700Nm 5.5-litre V8 supercharged CLS 55 AMG at $247,900. An entry 200kW/350Nm V6 CLS 350 will flesh out the range within three months with an expected price under $140,000.

Both the CLS 350 and CLS 500 boast Mercedes’ seven-speed automatic while the supercharged AMG has a five-speed auto. Mercedes claims the 1730kg CLS 350 will hit 100km/h in seven seconds and has a top speed of 250km/h, while the 225kW CLS 500 covers the same ground in 6.1 seconds and the supercharged CLS 55 AMG takes just 4.7 seconds.

Even though the car’s base architecture is based on the E-class, Mercedes engineers have managed to imbue the coupe with its own identity.

It boasts a wider track than the E-class, lower suspension, a modified high-performance braking system and sharper steering. It is, in effect, a taut and tighter E-class.

Standard equipment levels are high.

The entry-level CLS 350 boasts 17-inch alloys, 7G-Tronic, active bi-Xenon headlights, parking sensors, sports-tuned suspension, two-stage dual front airbags, side bags front and rear, curtain airbags, pre-safe leather upholstery, electric seats, cruise control, Comand navigation, six-disc CD changer, mobile phone pre-installation, full-size spare, steering-wheel mounted gearshift buttons, Thermotronic four-zone automatic climate control, tyre pressure monitoring and a tool kit.

About $10,000 in extra value above the E350 comes from the steering-wheel mounted gearshift buttons, Thermotronic, active bi-Xenon headlights and 17-inch five-spoke alloy wheels.

The CLS 500 adds 18-inch five-spoke alloys, Airmatic air suspension, heated front seats, a glass sunroof and television tuner. The range-topping AMG 55 adds bi-Xenon headlights, Harman Kardon surround sound system, TV tuner and an alarm with tow-away protection over and above the E55 AMG.

About 65 per cent of sales should favour the CLS 500, 25 per cent the CLS 55 AMG and 15 per cent the 3.5-litre V6. The 2006 forecast is for 420 sales, with the mix being mostly CLS 500 (50 per cent), CLS 350 (30 per cent) and CLS 55 AMG (20 per cent).

As for the question about what exactly defines a coupe – two doors or four? – when most people are asking "why?" Mercedes-Benz enthusiasts will most likely be asking "why not?". And that will be the secret of the CLS’s success.

As for the AMG version...

ALL self-respecting coupes include a high-performance offering in the line-up – and in the case of the Mercedes-Benz CLS, this is very definitely the CLS 55 AMG.

At $247,900 this high-performance CLS joins 12 other AMG offerings in the German car company's local line-up, which range in price from $159,900 for the 5.5-litre V8 C55 AMG right up to $459,900 for the 6.0-litre V12 CL65 AMG.

And, like its siblings, the CLS AMG will find a dedicated band of followers. Mercedes-Benz Australia has already sold 40 cars and expects to sell another 60 before the year is out.

The CLS AMG is driven by a 5.5-litre supercharged V8 that develops 350kW of power and 700Nm of torque. This endows the car with aggressive straight-line performance but AMG has added upgraded sports handling and Sensotronic brake control with eight-piston 360mm x 36mm front and four-piston 330 x 26mm rear ventilated discs all round to manage the extra power.

Mercedes-AMG engineers developed a new AMG sports suspension based on the semi-active air suspension Airmatic with adaptive damping system. Both the springs and dampers are stiffer than the CLS 500 and the three-phase adjustable shock absorbers help reduce body movements.

The CLS AMG also sits 10mm lower than other CLS models. The car's automatic level control ensures spring rates remain the same even with a full load, and also includes ESP. Tyre pressure monitoring is also standard.

The AMG accelerates from zero to 100km/h in 4.7 seconds, reaching 200km/h in 16.1 seconds, and has an electronically limited top speed of 250km/h.

The supercharged engine is similar to that adopted by the SL55 AMG and E55 AMG. A belt-driven supercharger and intercooler are located between the cylinder banks. They work together with a low temperature radiator in the front-end to achieve efficient cooling of the charge air.

As with other AMGs, the engine is mated to Mercedes' five-speed Speedshift automatic, which allows the driver to choose between full automatic or manual gear changes via the selector or steering wheel-mounted change buttons.

Visually, the AMG 55 is identified by a subtle bodykit, 18-inch light alloys, "V8 Kompressor" lettering on the front guards, quad exhausts and a discreet bootlip spoiler that reduces rear lift by 30 per cent to aid handling and high-speed stability.

In keeping with its sporty pretension, it also boasts a suitably luxurious interior. The electrically adjustable multi-contoured heated sports seats have "AMG" lettering as well as Alcantara panels at shoulder level which aid lateral support.

The AMG theme carries over to a 320km/h speedo scale, white-faced dials with red needles on the instrument cluster and an AMG sports steering wheel and gearshift knob. Polished stainless steel sports pedals with rubber studs complete the picture.

Standard equipment runs to matt silk burr walnut panelling, Thermotronic automatic climate control, active bi-Xenon headlights, alarm, space-saver spare with air compressor, Comand with DVD navigation system, a TV tuner and surround sound Harman Kardon Logic7 system.