We like
Quick and quiet roof mechanism, accomplished ride/handling balance, body rigidity and overall refinement, safety features, standard equipment levels, value

Room for improvement
Rear-seat and roof-down cargo accommodation break no new ground, well-sorted chassis could use more engine performance, sat-nav screen reflections, cabin wind resistance not as good as some

LEXUS has departed from traditional convertible-building convention by admitting it took a ‘top-down’ approach to producing its first open-top IS.

While most car-makers claim their respective convertibles are based on donor cars that were designed from the outset to accommodate a topless body derivative, Lexus highlights the lengths to which it has gone to transform the IS250 sedan into the IS250C convertible.

The “extensively redesigned” IS chassis features a maze of no fewer than seven underbody braces, as well as heavily reinforced A-pillar, bulkhead and rocker panel areas. In fact, the side sills are 29mm wider and 61mm higher, under just two doors that are some 300mm longer than the IS250 sedan’s front doors.

The result is an undoubtedly solid chassis that is easily a match for its most rigid rivals in BMW’s 3 Series (Coupe-) Convertible, as well as soon-to-be-replaced soft-tops such as the Audi A4 Cabriolet and Mercedes-Benz CLK Cabriolet.

With the roof in place, there is no hint of the ‘scuttle shake’ that afflicts many open-top vehicles, which offer inferior refinement and driving dynamics as a result. Take the roof off and the IS250C continues to feel flex-free, with only the vaguest hint of steering column deflection apparent over the roughest surfaces.

An extensive launch drive over some extremely rough roads in northern NSW and southern Queensland shows the IS-C, which features specific suspension hardware and tuning and is backed by the same responsive (electric) steering as the IS four-door, maintains the sedan’s well-sorted combination of compliant ride quality, agile handling and impressive overall body composure.

So much so that, even more so than the substantially lighter fixed-roof IS, the convertible IS feels as if it could handle far more power than its advanced direct-injection 2.5-litre petrol V6 offers. Thankfully, therefore, Lexus admits it is working on a 3.5-litre IS350C, but has ruled out a convertible IS F.

As with the IS250, all three IS-Cs come standard with steering wheel paddle shifters for the slick six-speed automatic transmission, which like the recently upgraded IS sedan, can be used to override the auto’s drive mode. Unfortunately, while they provide full manual control of the gearbox, they do not default back to drive mode after a certain period as other transmissions.

The IS-C’s party trick, of course, is a slick new three-piece folding aluminium roof, which was designed in-house by Lexus, drawing on its experience in developing the two-piece roof of its first folding hard-top, the aged SC430.

Unlike some convertibles, the IS-C roof matches its maker’s claim by opening and closing in precisely 20 seconds, which Lexus claims is best-in-class, using no fewer than 37 sensors and a total of 15 electric motors that are claimed to be quieter than the hydraulic motors traditionally employed.

Indeed, the sophisticated roof mechanism is extremely quiet and refined, and also operates the four side windows. Unlike some, it can only be activated when the car is stationary or travelling at less than 2-3km/h, but provides plenty of rear and rear three-quarter vision through its large heated rear screen, bookended by two relatively slender rear B-pillars.

Yes, the large folding hardtop seriously compromises a boot that has been expanded to accommodate it, with cargo space shrinking from a relatively massive 552 litres (175 litres bigger than the sedan’s!), to just 205 litres with it stowed. While that leaves room for just a couple of small soft bags with the roof down, Lexus says only one direct luxury convertible model has a (marginally) bigger boot.

The extra-large boot and longer rear overhang gives the two-door IS-C a more cab-forward body design than the sedan and doesn’t quite match the sleeker, flatter rear decklid of the 3 Series CC, but it retains the IS sedan’s striking wedge-shaped silhouette and gives it even more presence on the road.

Though it’s not apparent at first glance, the two-door IS also has a virtually all-new bodyshell, sharing only its bonnet, headlights and door mirrors with the sedan.

The sizeable folding roof also necessitated moving the rear seats forward (as well as inboard) by 45mm. Regaining 20mm of that lost rear legroom are new front seat with banana-shaped seatbacks, as well as a 20 per cent larger heated area.

It’s just enough to make the twin rear seats comfortable for adults, as long as the front-seat occupants are no more than 180cm tall, meaning the IS-C is as close to being a proper four-seater as any model in this class, but it’s still not capable of accommodating four full-size adults in comfort for a day’s drive.

Rear seat ingress/egress is aided by a one-touch tilt/fold mechanism that offers 29 degrees of seat tilt and 240mm of power-operated fore-aft action (which is claimed to be twice as fast as that on the sedan), while rear headroom is just 14mm less than in the sedan, thanks to a scalloped headlining design.

Of course, all four seats are clad in sumptuous leather trim and close attention has been paid to reducing sun glare in the open-top IS, including less reflective plastic over the deeply recessed instruments, but the large standard sat-nav monitor can still direct nasty reflections in direct sunlight.

Extensive sound-reduction measures have also been incorporated to make the IS-C as Lexus-like as the sedan, although the refined V6’s high-tech engine and exhaust note adds a new dimension to the topless IS.

Apparently a wind-blocker will become available as an accessory soon, which could be a useful addition for those who don’t need to transport rear passengers. Wind disturbance is also first-class with the side windows up, allowing relaxed conversation at highway speeds and easily passing the chief engineers’ personal requirement to be able to light a cigarette while on the move with the roof down. However, the IS250C’s interior isn’t as free from wind buffeting as other convertibles we’ve driven including Peugeot’s new 308 CC.

Otherwise, the Lexus appears to have achieved its goal of delivering best-in-class noise, vibration and harshness in the super-refined IS250C, which feels as crisp and involving drive to drive as the sedan but adds the split personality of both a stylish coupe and a convertible.

A range of clever new features shows a remarkable level of attention to detail in the development of the IS-C, which comes fully equipped at an $80,000 entry price that no comparable German convertible can match.

They include self-adjusting climate and audio systems, rear sensors that detect if there is enough room to open or close the roof, and side head/torso airbags to protect front-seat passengers in the event of a collision with the roof down, in addition to twin front knee airbags.

Both premium models add in a range of high-tech features more at home in top-end luxury sedans, including a pre-emptive pre-crash safety system and radar-operated active cruise control.

Throw in Lexus’ outstanding four-year warranty and after-sales reputation, plus a development regime that is said to have included 40,000km of gravel-road testing, including durability testing in Australia, and the IS250C emerges as a stylish, safe, refined, rewarding and value-packed new addition to the ranks of both the Lexus model range and the growing list of coupe-convertibles now available in Australia.