Sun beamer

First introduced in 1986, the new fourth generation BMW 3 Series Convertible goes on sale in the UK this weekend (exactly two years after the saloon version first appeared) and brings with it the shock of the new.

Yes, BMW has ditched the traditional rag-top and chosen the now favoured hard-top route to give the four-seater Convertible more of a sporting Coupe ambience, plus of course the additional benefits of more head room, better security and extra weather protection.

Out goes the fabric pram top and in comes a light weight (thin grade steel) three-section solid roof that automatically folds away (in around 22 seconds) into the boot with its own tonneau cover to tidy up the rear end.

Curiously, BMW supplies the Convertible in standard form with a remote control mechanism that only does half the job.

All versions allow the roof to be lowered by pressing the key fob, so you can instruct it to go topless before you get in. But closing the roof requires using the button inside the cabin.

However, if you opt for the Comfort Access pack the roof can be closed from the key fob as well. Additional functions here include perimeter door opening and AutoStart.

Having selected the folding hard top configuration, BMW faced the same problem as every other convertible maker - accessing the luggage space once the roof is tucked away in the boot.

Like almost every other design, the three-part roof sits in the top half of the boot, which then restricts access to the full load area - only very thin items can then be posted into the boot.

Volvo's solution on the C70 was to have a mechanism for raising the roof within the boot by a few inches leaving a letter box like opening - BMW uses a similar idea but has gone even further.

Pressing a button on the BMW 3 Series Convertible key fob opens the boot and lifts the roof completely out into a sort of half raised position and then returns the boot lid to its normal position allowing it to be opened in the conventional manner - the full operation taking about 10 seconds.

A luggage cover can then be released giving access to the full luggage space. Once items are in place the load cover is replaced and the roof can be returned to its out-of-sight location.

The major benefit is that the entire luggage compartment can be utilised and larger items stowed away (at 350 litres roof up and 210 litre roof down there is 50 litres more than before), the downside is the rather tedious and complex opening procedure.

Owners who need to carry more luggage can take advantage of a neat little feature - a fold down back section on the rear seats.

With the rear unoccupied (as it will be most of the time because of the tight knee room) the one-piece back folds flat and has a protective surface which allows suitcases or holdalls to be placed on it (restraining straps can be purchased separately).

There is also a load through hatch (normally called a ski hatch), which in the UK is more likely to be used to carry a set of gold clubs. Although two sets might be a squeeze.

Initially, the Convertible will be available in one SE specification level, but this become largely irrelveant almost immediately as more than 80 per cent of all those sold in the UK are traditionally supplied in full M Sport specification which is added next month.

Despite a £2,500 premium, the M Sport is in reality the only 3 Series convertible to have and comes with 18 inch M start-spoke light alloy wheels, high gloss Shadow line exterior finishes to the window surrounds, sport seats in cloth and Alcantara upholstery, brushed aluminium trimmings, M designation doorsill finishers, short shift M gearlever and M leather steering wheel while the suspension has been lowered by 15mm and fitted with stiffer springs.

Visually the new 3 Series Convertible looks intentionally very similar to the Coupe with the traditional BMW short overhangs, long wheelbase and short A pillar.

To this are added the trademark kidney grille, larger air intakes and bi-Xenon headlights that take up less space than conventional halogen headlights which allows the bonnet lip to be lower.

There is also a single waistline crease that runs front to rear passing through the door handles which ends up at the rear light clusters - the two piece LED lamps extending into the boot lid.

Conveniently, the metal top has provided the designers with the opportunity to re-introduced the famous Hofmeister kick in the C Pillar and at the same time give the Convertible 30 per cent more glass than with the fabric top which significantly increases rear visibility by 38 per cent.

Another benefit of the sold roof is that the cabin insulation is vastly superior, with the roof closed there are Coupe levels of soundproofing.

With the roof open the optional foldaway wind stop can be put in place above the two rear seats and proves to be particularly effective, and to keep things tidy, rollover protection is provided by pop-up bars that appear from the rear head restraints.

Overall the Convertible is 2 cm longer, slightly lower and squatter and has a sharper rear screen angle than the Coupe.

The Convertible can be instantly separated from the Coupe by one feature, and it's a rather curious one.

In every other folding hard top, the designers have made every effort to hide the folding mechanism by placing the folding mechanism on the inside, but at BMW the rear hinges are exposed and protrude slightly above the roof.

With no designer on hand to question at the UK press launch, BMW's marketing executives weren't entirely sure why this had been done but assumed it was for styling aesthetics rather than a practical necessity.

To distance the Convertible even further from the Coupe it has an exclusive interior with more space than ever before in a 3 Series Convertible and higher equipment levels (to make up for the 10 per cent price hike which reduces to a 2.9 per cent when the extra specification is taken into account).

Prime among the optional equipment list is a much-promoted world first - heat reflecting leather seating. This uses a special pigmentation that reflects infrared radiation in wavelengths more than 720 Nanometers - this can reduce temperatures on the seats by up to a massive 20 degrees.

Among the other features are ambient lighting, USB audio interface, satellite navigation and on cars fitted with the iDrive the ability to pre-programme up to eight favourite functions i.e. favourite radio station, regularly used phone number or most used route guidance location.

Despite an overall 55kg increase in weight (which is less than might be expected thanks to the use of lightweight materials such as plastic front side panels), better performance figures from the latest direct injection engines means that the Convertible is more powerful and more efficient than before.

On average, power has risen by 11 per cent, torque by 10 per cent while fuel consumption improvements are a massive 21 per cent with emissions reduced by 17 per cent. As a result VED gradings have dropped at least one band.

Arriving tomorrow (March 24), customers have the choice between the 325i (£33,065) and the 335i (£37,930) petrol units - shared with the 3 Series Coupe.

The 218bhp 325i sprints to 62mph in a very respectable 7.6 seconds and tops out at a highly illegal 152mph while returning the promise of 35.8mpg and emissions set at 190 g/km In six-speed auto configuration (borrowed from the Z4 Roadster andexpected to be the main transmission choice) the 325i proves to be a little laboured despite BMW's claims of reduced reaction times.

Pick of the openers is the six cylinder flagship 306bhp 335i especially in six speed manual form where is proves to be a real flyer thanks to its twin turbochargers.

And it sounds as good as its performs as it completes the 62mph dash in a follicle depleting 5.8 seconds before being limited to 155mph all accompanied by a deep bark from the twin exhausts.

Admittedly it's a lot thirstier, consuming unleaded at the rate of 28.5mph and its less kind to the environment at 238 g/km, but the extra performance potential makes it the rear thriller.

These will be followed next month by the entry level four cylinder 170bhp 320i (£30,630), the straight six 272bhp 330i (£36,395) which is mechanically similar to the 325i but with a higher state of tune and the lone diesel alternative the impressive 231bhp turbocharged 330d (£36,770) which will sprint to 62mpg in 7 seconds.

Based on previous experience the 320i likely to be the best seller purely in terms of being the entry level price model while in the third generation diesel accounted for 30 per cent when there was two diesels to choose from.

To prevent Coupe owners transferring their affections in droves to the Convertible, BMW has deliberately given the latter a soft on-road character.

It's comfortable and more suited to cruising than sprinting but is good natured and assured with BMW's 50 / 50 weight distribution giving it s nice balanced feeling.

All versions are supplied with larger brakes than before (thanks to the use of 17inch wheels) and BMW's traditional rack and pinion steering is as precise and direct as ever.

Customers have the option of BMW's Active Steering which increases or decreases the assistance depending on the speed of the car to assist low speed manouvering becoming progressively more direct.

This also works in combination with BMW's Dynamic Stability Control + (DSC+) which intervenes to counteract signs of oversteer. This is supplemented by; brake dying, brake pre-tensioning, soft stop, hill start assist and brake fade compensation.

With the UK the second best market in the world for the Convertible, BMW expects to sell 5,800 Convertibles this year with more than 40 per cent already sold.

The use of a hard top does nothing to detract from the fresh-air fun of the 3 Series and with the top-up takes it deep into Coupe territory adding a new dimension, which should keeps it at the top of the class.