The surprising secrets of BMW’s new 4 Series Convertible

BMW went soft with the new 4 Series Convertible. We found out why… 

11 May 2021 Update: The BMW 4 Series Convertible is officially on sale in Singapore from today, with the 420i Convertible M Sport Pro now commanding S$266,888 with COE and the more powerful BMW 430i Convertible M Sport Pro going for S$305,888 with COE

SINGAPORE — BMW will pull the covers off its new 4 Series Convertible in Singapore this month, and whatever you think of open-top cars, the German premium carmaker seems to regard the people who drive with fondness. Emanuel Varga, the product manager for the new 4 Series Convertible, calls them a “truly exclusive and very special customer group.”

Singapore is getting 420i M Sport and 430i M Sport Pro versions. Both have a 2.0-litre turbo engine but in different states of tune: 184 horsepower and 300 Newton-metres of peak torque for the 420i, and 258hp and 300Nm for 430i. That translates into 0-100km/h times of 8.2 and 6.2 seconds respectively.

The Convertibles list for S$246,888 (420i) and S$285,888 (430i) with certificate of entitlement. That’s S$19,000 and S$10,000 more than you’d pay for the Coupe versions of each respective car.

Prefer a roof over your head? It’s the 4 Series Coupe for you…

For the extra money you get all the visual drama of the current 4 Series Coupe, with the ability to bare your face to the wind. Touch a button and the 4 Series Convertible’s soft top folds away in just 18 seconds, and it works on the go, as long as you keep things slower than 50km/h.

But talking to BMW folk, you get the feeling they would almost prefer you to keep the top up so everyone can see it.

Thomas Roth, the new car’s project head, calls the roof its main innovation. It replaces a folding metal roof in the previous 4 Series Convertible, and though it’s a return to a more traditional way to give a car an open top, BMW says it’s anything but old fashioned.

“We decided to go back to the soft top because we now have the technology to combine the best of two worlds,” he said in a virtual conference. That tech is a “panel bow” design, a light, rigid arrangement that gives the roof its shape and structure. 

“We have these bow panels that are really connected to each other, and they are stiff, they are light of course and they are very clean, which means, you see a kind of hardtop and coupe character,” Mr Roth said.

Conventional soft tops use a series of rods that support the soft material stretched over it. That traditional design has its advantages: it’s relatively light and doesn’t take up much room. The downsides have to do with noise and temperature insulation, and the fact that the soft roof material sometimes sags between rods.

Folding metal roofs are the opposite: secure, quiet and well-insulated when up, but bulky when folded and relatively heavy.

BMW says the new roof is 40 percent lighter than the hardtop that engineers gave the last 4 Series, and the bow panel design solves the other ragtop problems. “If you drive on the motorway, there’s exactly the same level of noise like in a coupe,” said Florian Moser, a spokesperson for BMW. “It’s really amazing.”

Then there’s the idea that a convertible should look like, well, a convertible. “The car body is shiny, with this metallic paint, and the soft top is fabric basically. So, what that combination brings is a very intriguing contrast,” said Lim Seungmo from BMW Design. The contrast between a fabric roof and metal body adds that touch of exoticness you’re supposed to feel when you see a convertible, he said.

The fact that the fabric doesn’t sag means the 4 Series Convertibles’ roofline is exactly as BMW’s designers intended. “The panel bow system underneath (enables) the design without any sagging or tent-like, hanging effect, which the conventional convertible used to have, so now the new 4 Series Convertible has perfect tension with this canvas top,” Mr Lim said.

On a more practical note, the new roof leaves more space for cargo: the car’s boot is 80 litres bigger than its predecessor’s.

Project head Roth also said the lighter roof means a lower centre of gravity, which in turn makes the car handle better. That’s something we’re looking forward to finding out for ourselves.

Yet, the fact that it had a metal roof didn’t seem to harm the last open-top 4 Series. BMW sold more than 800,000 of the previous 4 Series cars, and roughly 15 to 20 percent were Convertibles, according to Mr Varga, the product manager. Unusually, sales of the car actually started to pick up towards the end of its product cycle. 

In any case, open top cars occupy something of a special place in Munich. “BMW has a longstanding tradition with convertibles. It started back in the 1930s. And since then, the passion for convertibles hasn’t receded, so we truly believe that the convertible segment is something worth investing in,” Mr Varga said. 

Given that BMW built just two models with folding hardtops in nearly 90 years, the new 4 Series Convertible’s fabric roof is a return to form. “Actually, it’s clear,” Mr Moser, the spokesperson, said. “A true convertible needs a soft top.

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Leow Julen
CarBuyer's managing editor is a lot older than he behaves. He's been writing about cars for 26 years. Someday he might do it coherently. Ju-Len believes in world peace and V8s, but not necessarily in that order.