Lexus is rightly proud of the stunning convertible version of its sleek LC Coupe, but is it the “perfect soft top” as the luxury brand claims?
The design goal was for the new model to have its own identity as a convertible, while retaining the distinctive lines of the LC coupe.
When raised, the soft top creates a smooth silhouette, echoing the profile of the coupe. No frame elements are visible and there are no obtrusive joins between the window glass and the canvas. The material has a multi-layered construction that provides excellent soundproofing, so a quiet cabin ambience is preserved.
The roof is operated using a hydraulic mechanism that gives consistent, reliable performance. Raising and lowering the roof takes just 15 seconds, but speed was not the primary aim. Lexus focused instead on operation that reflects the quality that defines the brand, engineering a slight pause before the main part of the roof movement begins. This is inspired by the hiatus that is part of the traditional execution of Japanese calligraphy.
The top can be operated when the car is moving, at speeds up to 30mph. To ensure it can cope with external factors such as headwinds, it was tested in a wind tunnel at up to 56mph. Wind tunnel tests confirmed the car could be driven at a maximum speed of almost 250mph.
In an example of Lexus’ human-centred design thinking, the hydraulic soft top was rigorously tested for reliability and fail-safe operation, so owners can have peace of mind about its lasting quality.
Where durability is concerned, testing parameters for repeat opening and closing are usually based on the assumption the mechanism will be in use for around 10 years. Lexus went much further, taking the system to breaking point. The roof went through around 18,000 cycles before a problem was encountered; even then, this was not a hazardous issue.
The stowing of the roof presented significant challenges: it had to preserve the convertible’s silhouette when raised, but at the same time allow for a reasonable amount of space in the luggage compartment when lowered. The design goal was also to maintain a streamlined area around the car’s rear shoulders, avoiding the bulkiness found on some convertibles. These issues meant the roof had to fold into an unprecedentedly small space.
To achieve this, the team devised an innovative four-fold system, which, although a more complex design, allowed the roof to be stored between the rear suspension towers. Special stoppers were added to prevent any damage from interference between the soft top and surrounding parts.