2015 BMW M235i Convertible auto UK first drive

What is it?

It's the wind-in-your-hair version of BMW's high-performance M235i, sporting the same 322bhp turbocharged six-cylinder petrol engine as the coupé.

You know the drill by now: a car losing its roof gains weight in an attempt to improve rigidity. In this case, the M235i Convertible is up by 145kg over its fixed-roof stablemate.

That sounds like a lot, doesn't it? Well, there isn't as big a performance penalty as you'd expect. The soft-top hits an identical limited 155mph top speed and still scampers to 62mph in just 5.0sec in auto form - just 0.2sec behind the coupé. 

However, also up is the price, because going for the convertible M235i adds £3175 to the price. That's a decent hike by any measure, and one that places it in direct contention with Audi's S3 Cabriolet.

What's it like?

The M235i Convertible is huge fun. Let's be clear, though: it doesn't offer the agility or surefootedness of the coupé - or BMW's M135i hot hatch, for that matter.

Unsurprisingly, the turbocharged 3.0-litre straight six engine is the hero once again. It's a brilliant thing, providing a huge slug of torque from revs so low that you can simply forget to change down a gear and still get away with it. Maximum power arrives at around 5800rpm, but the wait is minimal thanks to its free-revving nature. 

It's an engine you'll want to rev, too, because its six-cylinder roar, accompanied by a whistling turbo and interrupted by the popping from its exhausts on the overrun, is seriously addictive.

While less involving than the manual version, the eight-speed automatic M235i is still very good, picking up power quicker than many of the VW Group dual-clutch devices and always remaining smooth. The gearbox is quick to respond to manual changes, too, both up and down. 

Unfortunately, its ride and handling blend lets the M235i Convertible down. The steering, while relatively numb, is at least quick and accurate, but the way in which the body squirms over mid-corner bumps and camber changes tends to unsettle progress in a way never experienced in the coupé.

Cross-country progress is still quick, of course, but start to push hard through chicanes and the convertible's extra weight starts to reveal itself. Even flicking the car's driving mode to Sport to firm up its dampers doesn't manage to conceal it, even if vertical movement is improved.

With the adaptive suspension on a softer setting and at city speeds, the ride is firm but controlled, and occupants are well sheltered from the elements when the roof is down (a process that takes 20 seconds at road speeds of up to 30mph). The cabin is standard 2 Series, so the level of quality is high - if not quite on a par with Audi - and there's plenty of adjustment on the driver's seat and steering wheel.

Standard equipment is generous, too, and BMW's brilliant iDrive multimedia controller comes as standard. However, there's a fair bit of tyre roar to contend with inside at motorway speeds with the roof raised. 

Should I buy one?

Being able to hear the M235i's engine note even more clearly is certainly a tempting proposition, and the way you're able to point-and-squirt the auto model in particular is attractive, considering the ballistic performance that's just a prod of the accelerator away. Only the fact that it can lose its composure in corners lets it down.

Is it better than an Audi S3 Cabriolet? Not in terms of interior quality or efficiency, no, but the BMW's more powerful engine is infinitely more characterful and its adjustable rear-drive handling is preferable.