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A new leather-tanning process unveiled on BMW AG's fourth-generation 3-Series convertible could get drop-top drivers out of the hot seat.

The new retractable hardtop, which goes on sale in Europe on March 24 and one week later in North America, features leather interiors with Sun Reflective technology, the auto maker boasts.

Leather pigments are infused with a metallic component in conjunction with the tanning process, says Albin Dirndorfer, BMW's newly appointed director of driving dynamics and a major force behind the convertible's development.

This specially treated leather reflects sunlight's infrared radiation at wavelengths of more than 0.0003 ins. (720 nanometers). The result is a temperature reduction of up to 68° F (20° C) on darker leather and somewhat less on lighter colors.

BMW's key consideration, Dirndorfer tells Ward's, was to ensure the reflective leather maintained proper color intensity and gloss levels, regardless of viewing angle. This was achieved after extensive testing, he says.

All leather surfaces, from door panels to consoles, feature Sun Reflective.

The patent for Sun Reflective's technology is shared by BMW and its leather suppliers, Bader GmbH & Co. Kg and Branaa GmbH, both of Germany.

Dirndorfer says the auto maker has exclusive use of the technology for at least one year.

The new convertible also features more shoulder and elbow room — 3.2 ins. (8 cm) and 4.7 ins. (12 cm), respectively, than the previous model.

In addition, the car has a fold-down, rear-seat backrest. This is designed to shield the car's upholstery and provide additional cargo space.

The fold-down backrest also provides access to a pass-through wide enough to accommodate snowboards. A ski/transport bag and matching BMW luggage is available.

There are two powertrain options: a 230-hp 3.0L I-6 and a 300-hp 3.0L twin-turbo I-6, which debuted last year on the fifth-generation 3-Series coupe. Both are on this year's Ward's 10 Best Engines list.

Pricing starts in the low $40,000 range in the U.S. and €39,900 ($51,649) in Europe, where there are three additional powertrain choices. They include a new 4-cyl. I-4 with start/stop capability that conserves fuel at idle and a 6-cyl. diesel-powered I-6.