Review of the new BMW 3-Series Convertible

Lots of car manufacturers have their own special ways of doing things, longstanding approaches to design or engineering around which the identity of their brand has been forged. There can come a time, however, when it's necessary to make breaks with tradition. BMW's decision to fit a folding hard-top roof to its 3-Series Convertible, abandoning its hallowed 50:50 weight distribution in the process, was one such move. The purists were predictably up in arms but it didn't prove to be the hammer blow to BMW's reputation that many suggested. Today, the 3 Series drop-top is as popular as ever and the latest facelifted cars should only add to that.

Engineering any folding hard top means putting a good deal of metalwork and motors in the rear of the car but BMW wanted to do it anyway for its 3 Series. That meant a few engineering headaches though. It was impossible, for example, to use this kind of roof, yet still achieve the kind of perfect 50:50 weight balance that BMW insists on for other models in its range. But does anyone really care if the 3 Series Convertible has a rearward weight bias? Porsche 911 owners rarely complain. By the same token, will anyone really care that the latest models have minor visual tweaks, that the 335i petrol model is more efficient and that the 320d and 325d diesels have a little more power and torque? Maybe not, but BMW have done it anyway.

BMW has an annoying habit of continually tweaking its engine range, making the available units more powerful, more economical or more often, both. Well, it's annoying for rival car manufacturers. For the car buying public, it's great. Here's a case in point. For the revised 3 Series Convertible range we're looking at here, there's slightly more power for the 320d and 325d diesel versions that many customers choose, plus more efficiency for the potent 335i petrol turbo variant.

These days, the 3-Series Convertible petrol line-up starts with the 170bhp 320i, then comes the 218bhp 325i model, which sits just below the 272bhp 330i derivative. At the top of the pile sits the convertible version of the legendary M3 but the turbocharged 335i variant offers much of what makes the M3 so great - for a lot less money.

".it's hard not to be impressed at the way the German marque has executed its complex canopy"

Ignore the badge on the back: this is no 3.5-litre unit. Instead it's a turbocharged 3.0-litre powerplant with Valvetronic variable valve management and direct injection technology that accelerates from rest to sixty in just 5.8s. A seven-speed double clutch transmission is also available for enhanced performance and economy. Although power and torque remain the same with the revised version of this engine (a hearty 306hp and 400Nm), consumption and emissions have been significantly reduced. This has been made possible by combining a single turbocharger with VALVETRONIC variable valve management and High Precision Direct Injection for the first time

That leaves the diesels. These start with the 184bhp 320d and the 204bhp 325d, both with another 7bhp and 30Nm more of torque, good enough to shave around half a second from the rest to sixty sprint times. Then comes diesel flagship, the 242bhp 330d.

This is the facelifted version of the latest 3 Series Coupe, so there are a number of visual differences between this and the original folding hard-top version. Most noticeable is the single air-intake sliced in below the front bumper with matt aluminium fins mounted within it. Its effect is to visually lower and widen the car for a more planted and sporty stance. It appears to work. Other features include the revised headlights with LED corona rings and red LED rear lights.

The folding metal roof itself remains unchanged. It's a three rather than a two-piece system. The advantage of this is that you don't need a distended rear end on the car to accommodate the larger sections of a two-piece roof. The downside of stacking three pieces atop each other instead of two in the boot is that when they're folded, there's not a great deal of luggage space left. With the roof in place, you'll get 350 litres of load space. Fold it down and 140 litres is instantly pared from that figure.

The operation of the roof takes a so-so 22 seconds but there are some real practicality benefits offered. Because of the larger glass rear screen and side windows, visibility has improved by 38 per cent when compared to this car's soft-top predecessor. Not only does this mean that rear seat occupants will feel less claustrophobic, it's also an important safety feature, with cars and bikes less able to sit in your blind spot on motorways. The designers have also factored in some key practicality benefits too. The rear seat backrests can be folded flat to provide additional luggage space if the 210 litres in the boot isn't cutting it. As an option, customers can also specify a through loading facility for bigger items that can still be used with full folding hard top functionality.

The standard 3 Series Convertible comes in SE trim and that gets buyers 17" alloy wheels, cruise control, xenon headlights with built-in daytime running lights, Dakota leather upholstery and dual-zone air-conditioning. It's fairly comprehensive but then, you'd expect that at the prices BMW is asking. The M Sport trim level comes at a hefty premium of around £2,500 but it does much to enliven the look of the car. The M aerodynamic bodykit is added, as are 18" alloy wheels, while various M-Sport accessories pop-up inside.

There are plenty of other convertible models out there on the market but it's the fabric-topped Audi A5 Cabriolet that stands out as the biggest direct rival to the 3-Series Convertible. Otherwise, buyers without the need for four seats might be attracted to the crop of modern roadsters which include BMW's own Z4, a car that followed this 3 Series in fitting a folding hard-top roof.

The economy figures that BMW is able to squeeze from its engines really do put its products on a different level to most rivals and the 3 Series Convertible is no exception. The improved diesels shine particularly brightly with the revised 320d now returning an outstanding combined cycle 55.4mpg and 135g/km emissions, while the respective figures for the enhanced 325d are 49.6mpg and 151g/km. Even the powerful 330d can manage 46mpg and 162g/km, while the petrol options are hardly profligate either. The 43mpg 320i has 159g/km emissions and the automatic-only 335i is now significantly more affordable to own, returning 32mpg with 205g/km emissions. The automatic transmission option has only a small negative impact of around 2mpg on the fuel economy of most engines and it's likely to continue to prove a popular choice.

There will always be those who think that a folding hard-top roof isn't the kind of thing that a brand like BMW should be fitting to its vehicles. It isn't exactly top of the list of features that you'd expect to find in the Ultimate Driving Machine. That said, it's hard not to be impressed at the way the German marque has executed its complex canopy. The 3 Series Convertible largely solves the styling issues that affect many folding hard top cars and looks better than ever in its latest facelifted form.

Convertible buyers are used to having to accept some compromises in terms of ride and handling but the 3-Series Convertible copes remarkably well in the absence of the extra rigidity afforded by a fixed roof. The cohesive styling, the standout engine range and the general solidity of the product also warrant a mention and help make this just about the top model of its type on today's market.

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