First look: Lexus takes the lid off its IS convertible

LEXUS unveiled the much-anticipated convertible version of its IS series at the Mondial de l’Automobile in Paris this week, complete with a folding aluminium roof that comes with a claim of the fastest opening time – 20 seconds – for a three-part roof design.

As GoAuto reported in August, the IS250C 2+2 is due on sale in Australia late next year and is expected as a single model variant priced around $100,000. With no news at this stage of a high-performance F-branded version, the IS coupe-cabrio will arrive, as expected, with the regular sedan’s 2.5-litre V6 engine and six-speed automatic gearbox combination.

And it should be a wonderful addition to the Toyota luxury division’s stable, if all the claims being made in Paris this week hold true.

These include “uncompromised driving dynamics”. Noise, vibration and harshness (NVH) performance that is “on a par with that of the IS saloon”. And “a large boot space, together with easy rear seat access and generous accommodation for rear passengers”.

The latter owes much to the compact packaging of the three-part roof, which is made entirely of aluminium, has full electric operation and includes a unique “roof brake” safety device which during the closing stages slows the roof down as it approaches the top edge of the windscreen.

Lexus designers have managed to keep the drag coefficient to 0.29Cd (measured with the roof in place), which is well within sight of the sedan’s 0.27Cd and illustrates some extensive work that has gone into minimising wind turbulence when the roof is lowered.

Points to note include the steep-angled windscreen, smooth cabin profile, aero-oriented “duck tail” rear styling (which gives an “air kick” effect), a redesigned tail-light cluster (with LEDs), and a series of covers on the underside of the vehicle.

According to Lexus, the only body panels shared with the IS sedan are the bonnet, headlights, doorhandles and mirrors. The remainder have been redesigned to harmonise with the roof, such as the rising belt line that kicks up towards the rear of the car when viewed from the side profile.

The front double wishbone and multi-link rear suspension continues, although “significant chassis revisions” – details of which are still to be released – were made to ensure a ride comfort “suitable for a convertible” and also a “consistent dynamic performance”.

Lexus claims that extensive temperature, vibration and shaking tests were carried out to ensure the changes to the bodyshell and chassis maintained NVH characteristics akin to the IS sedan.

It also maintains that “class-leading low wind noise levels” are achieved through measures such as acoustic windscreen glass and the detail design inherent in the roof, door and window panel seals.

A five-star front impact rating from Euro NCAP is anticipated, following numerous changes to the body structure that are said to enhance collision strength, rollover protection and torsional rigidity.

Other safety measures onboard include energy-absorbing side impact pads for both front and rear occupants, and larger side airbags that provide head protection in the event of a side impact. The electronic stability control system was tuned for open-top driving, with shorter stopping distances on road surfaces with uneven levels of grip. A revised pre-collision system will also be available.

The four-seat cabin is based on the IS sedan, although the demands of open-top driving has forced a redesign of the instrument binnacle and reconfiguration of the premium stereo and climate-control units. The latter also includes a speed-sensitive control, which increases airflow when the roof is lowered and further increases it in line with vehicle speed.

The doors are 300mm longer to provide a wider aperture for good rear-seat access, while a one-touch walk-in button control that folds and slides the front seats forward is a welcome feature. The rear seats are set 30mm further inboard than in the sedan to optimise headroom, while slim-profile front seats maximise rear legroom.

As well as the compact packing of the folding roof, a 50mm longer rear overhang (compared to the sedan) was created to assist with boot space.

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