BMW's large but line-heavy Gran Coupe

The line-heavy BMW 8 Series Gran Coupe becomes the third model to wear the current 8 Series badge.

The Porsche Panamera/Mercedes-Benz CLS/Audi A7 rival is derived from BMWs group rear-drive platform, rather than any standalone sports car architecture. It will run the same suite of engines as the coupe and convertible versions, which should result in an M8 version as well.

The four-door Gran Coupe gets a 201mm wheelbase stretch over the coupe and into luxury territory. After all, the coupe’s rear legroom was desultory at best.

Long and sleek, the Gran Coupe tips well over the five-metre barrier at 5,082mm long (up 231mm on the coupe) and is 61mm taller than its two-door counterpart. It’s wider than the coupe, too and considerably wider at the rear than the front.

The A-pillars are significantly steeper than the coupe’s and leads to a roofline designed more to deliver front and rear headroom than the coupe’s uncompromising angles.

From there, though, it becomes awfully line-heavy. There is a variety of horizontal shapes and creases in the side bodywork, plus a pair of weird fins on the C-pillar that lead into the boot from the roof.

Its front end runs adaptive LED headlights (with optional laser versions) and slim line LED rears lurking among no less than 16 horizontal lines before your eye arrives at the top of the boot lid.

The pair of trapezoidal, chromed exhaust tips deliver the gases from a three-engine range (at least initially), topped by the 4.4l V8 of the M850i xDrive version.

Identical to the coupe and convertible, the M850i’s V8 gives the Gran Coupe 390kW of power and 750Nm of torque, hurling the all-wheel drive four-door to 100km/h in 3.9 seconds.

There’s also a version of BMW’s classical straight six in the 840i xDrive, with 250kW of power and 500Nm of torque from the turbocharged 3.0l engine. The new six pot is 6kg lighter than its predecessor, helping it to 100km/h in 4.9 seconds, though the rear-drive version takes 5.2 seconds.

There’s also a diesel that’s almost as quick as the 840i, with the 840d xDrive ripping to 100km/h in 5.1 seconds. It throws out 680Nm of torque as the headline figure, backed up by 235kW of power.

The 840d is, unsurprisingly, the most frugal of the four powertrains, despite its heavy all-wheel drive setup, with a combined consumption figure of 6.2l/100km, with the M850i providing the bookend at 10l/100km.

The two 840i models take the middle ground, with the rear driver posting 7.5l/100km and the xDrive lifting that to 7.8 l/100km.

All three motors will mate to the ZF-built eight-speed automatic transmission, complete with paddle shifters on the steering wheel to deliver manual shifting.

While the 840i is available as a rear-driver (with an active M-Sport self-locking differential), the rest of the launch powertrains include the latest all-wheel drive system to give them a rear-bias in their power delivery, and the M850i can also be specced with the M-Sport differential.

At 1,800kg, the 840i is also the lightest of the three launch options and about 70kg heavier than the two-door version. Though that’s still awfully weighty, it’s about the norm for the category these days, and the xDrive system adds 55kg to take it to 1,855kg.

The V8 M850i’s weight climbs to 1,995kg (an astonishing 195kg jump), while the diesel-powered 840d is 1,925kg.

BMW has tried to tie this all down with adaptive dampers, with active steering in the all-wheel drive models. Active roll stabilisation is left as an option with the M Professional suspension package.

The braking systems are identical to the coupe’s, combining four-piston fixed calipers up front and floating single-piston units at the rear, though the V8 includes more powerful M anchors.

The rubber package on the M850i includes 20-inch alloys with 245/35 front tyres and 275/30 R20 rears.

Inside, BMW claims the rear seats are “even more comfortable to travel in”, which is a relief because the coupe’s rear seats simultaneously attempted to break my ankles, knees and neck.

Besides extra space, three electric sunblinds and four-zone climate-control air conditioning also help the Gran Coupe’s rear passengers.

The centre console is stretched into the rear, making the Gran Coupe a 4+1 design, rather than a true five-seater. It has electric seats in the front, plus a 40:20:40 split in the folding rear seat that opens in to the claimed 440l luggage area.

The attempts at saving mass are heavily pronounced in the cabin, even more so than the body. While the body has a plastic bootlid (like the Z4), the interior boasts a magnesium dashboard-supporting bracket and carbon fibre in the centre tunnel.

But there are further weight-saving options, the most significant of which is the carbon fibre roof (which also helps the centre of gravity). The rear diffuser, the mirror caps and the bars on the air intake can all be switched to carbon fibre, too.

The interior tech starts with BMW’s 7.0 operating system, which includes a “Hey, BMW” spoken function to help with a surprising range of commands.

The high-resolution instrument cluster runs to 31cm, while the infotainment screen moves to a 26cm unit.

While there is a touchscreen function, BMW also includes simpler redundancies, including the voice commands as well as the iDrive scroller, gesture control and function buttons on the steering wheel.

It stands pat on the practicality stakes with just a pair of cup holders, a single 12V socket and one USB port in the front, though there’s also a wireless charging tray for just about anything that isn’t made by Apple.

There are more USB ports in the rear and under the centre armrest, plus some top-shelf audio equipment. The Live Cockpit Professional option brings with it the fully digital instrument cluster and a 20GB hard-drive memory system.

Its audio suite ranges from a standard 205W system with nine speakers to a 464W, 16-speaker Harmon Kardon surround sound unit to a Bowers & Wilkins surround sound setup with a 16-channel amplifier, 1,400W, dynamic equalising and 16 illuminated speakers.

The BMW 8 Series Gran Coupe will be launched in SA in October, in M850i xDrive, 840i and 840d xDrive versions.