19 November 2021
What is it?
First, it was the manual gearbox that fell by the wayside. Then it was rear-wheel drive. So your only choice for a BMW M4 Convertible today is a four-wheel-drive automatic. And you know what? That’s great.
The powersliding enthusiast can still buy a rear-drive coupé, or just put the xDrive system in rear-wheel drive mode, and the purist is likely to be catered for by the upcoming M2. What you’re left with is a drop-top M4 in the spec that most people were going to order anyway.
The big news with the convertible M4, or to give it its full name, the M4 Competition M xDrive Convertible, is the same as with the regular 4 Series Convertible: gone is the metal folding roof. Instead, you get a fabric top. You might hope that saves weight, and BMW does claim the roof itself is 40% lighter than the old model’s. However, because the 4 Series has grown so much and gained that four-wheel drive system, the whole car is actually heavier than before, weighing a portly 1920kg. That’s also 145kg more than an M4 xDrive Coupé.
More so than the weight, the fabric roof benefits the styling. Since the boot no longer needs to hold three metal roof sections, the whole rear deck can be lower, more shapely and more like the coupé. The roof itself can also have a more attractive shape. Indeed, in the metal, it’s quite an elegant shape and a lot sleeker than the slightly saloonish old model. And yes, it has The Grille. Has enough time passed yet that we can admit it looks quite good? The fabric roof also enables more boot space – up to 300 litres when the top is folded, 80 more than in the old model. When the roof is up, that increases to 385 litres.
As with most convertibles, the majority of the additional weight comes from bracing to get back some of the fixed-roof equivalent’s torsional rigidity. As such, the M4 has an aluminium shear panel in the front-end structure, underfloor bracing elements and a rear axle subframe with a rigid connection to the body.
Power is provided, as in all other M3 and M4 versions, by the familiar 3.0-litre straight six with 503bhp at 6250rpm and 479lb ft at 2750-5500rpm. Despite the weight, it still powers to 62mph in a faintly ridiculous 3.7sec.
What’s it like?
Those specifications suggest quite a hardcore, serious performance car, so the question is how that lies with the more relaxed, cruiser character of a convertible.
Superficially, it feels very similar to any other M3 or M4. You’re looking at the same dashboard, and the beautifully made and user-friendly interior and iDrive system; you’re sitting in the same brilliantly supportive but slightly silly carbon bucket seats (more normal seats with an Airscarf-type system are standard); and there is the same firm ride and relatively high level of road noise.
It’s still a car you would be very happy to use every day, though, and having a fabric roof rather than a metal one changes very little in that respect. You would be hard-pressed to notice the 0.2sec penalty in 0-62mph acceleration compared with the coupé, because it feels just as unusably accelerative.
The xDrive system is also perfectly integrated. Leave everything in Comfort mode and traction is absolute, but engage M Dynamic mode and, particularly on a cool autumn day, it will feel as rear-wheel drive as you could ever want on the road. Out of tight corners, a wiggle of the hips can be enjoyed with total confidence because it’s nice and progressive, and you’re never on your own. As with other xDrive M cars, you can turn the stability control all the way off and put it in rear-wheel drive mode, but given how playful it already is in the halfway mode, that’s something best left for the track.
Where the M4 convertible can come undone is on particularly uneven roads. Here, you can feel the lack of torsional stiffness as the steering column feels like it’s moving about and the whole car gets messily deflected by bumps in a way that the hard-top version doesn’t. The steering precision and feedback that are normally there come and go with the terrain, too.
We’ve said previously about the coupé version that the stiffer suspension settings are worth using because the body control gains outweigh the small reduction in absorbency, but in the convertible, they just exacerbate the body stiffness issues.