Although many of us consider BMW an exemplar of savvy marketing, in-depth product development and peerless focus on functionality, until rather recently they had something of an Achilles heel. They were lousy at building sports roadsters. The Z8 never caught the imagination, most preferring the M5 saloon upon which it was based. The Z3 - even at its M Roadster zenith - never had the chassis its range of engines deserved. The Z4 shows what BMW can do when they set the collective mind to it.

Take the 2.5-litre cars we examine here. When the Z4 was first launched in the UK, the 2.5i was positioned as the entry-level car, although a 2.2-litre model was available for a while and a 2.0-litre unit arrived to take over as the base option. With no fewer than 192bhp to call upon, it was a far cry from the entry-level Z3 with its 118bhp sewing machine. Priced at over £27,500 it was also a long way removed from the Mazda MX5 market that formed the hunting ground for the Z3. Today, the engine is offered in two forms, the 177bhp 2.5i and the 218bhp 2.5si. Together, these Z4s have a bunch of far tougher targets at which to take aim. Cars like the Honda S2000, the Nissan 350z Roadster and even the Lotus Elise represent a stern task for the Z4 2.5 and against talented opposition like this, the boldly styled Bavarian must either put up or shut up.

Although the Z4 differs greatly from its predecessor, it's well worth noting that when the Z3 was launched there was a considerably body of opinion that slated its appearance, much as there are no shortage of commentators who dislike the Chris Bangle penned Z4. With its snarling front and weak, fishy tail the Z3 looked like two designs welded together. The Z4 looks like twenty-two designs agglomerated into one. It's an unusual car, but spend a little time with it and you'll see the genius in its styling. This is a car that really does grow on you, challenging the eye with its so-called 'flame-surfaced' flanks and its unorthodox detailing and proportions. The latest model can be spotted by the shoulder line that extends beyond the bonnet edge to the front air dam. There's a wider air intake below the grille, which itself displays some minor modifications and the rear tail lights feature horizontal light conductor rods as seen on the Z8. Of course, there are those quite happy with unchallenged eyeballs and no amount of waxing lyrical about the styling will convince those that find the Z4 beyond the pale. Their loss.

This is, after all, a proper sports car. The 2.5si model will sprint from rest to sixty in just 6.5 seconds on the way to 149mph, all the while accompanied by BMW's trademark straight six growl. Tipping the scales at just 1,260 kg does wonders for the power to weight ratio, BMW having sought lightweight componentry wherever possible. An example is the suspension system. Whereas the Z3 used the ancient semi-trailing arm suspension of a 1985 vintage 3-series, the Z4 is bang up to date, using a proper alloy multi-link arrangement. The Z4 sits foursquare on the road due to a wide track at the front and rear. It was the first BMW to use electric power steering and is hugely torsionally stiffer than the somewhat wobbly Z3.

"It's an unusual car, but spend a little time with it and you'll see the genius in its styling"

The commitment to making the Z4 a proper driver's car can be seen in certain key areas. The traction and stability control systems can both be disabled at the touch of a button, something you won't be able to do in a Mercedes SLK for instance. Although it does require you to hold the button in for what seems like an eternity when the control systems are disabled, you'll be aware quite how potent the 3.0-litre in particular is. BMW's paddle shift six-speed automatic gearchange can also be specified with the 2.5si and 3.0si cars. If the exterior design generates a little controversy, the same can't be said of the cabin styling. It's typically low-key but classy, BMW at their best. There's a broad centre console and clear dials. Space in the footwell is especially generous and it's possible to hunker down into a low driving position and feel really ensconced in rather than on the car.

Drive the Z4 at seven tenths and it will feel a million dollars. The chassis feels good, the ride supple yet well damped. It's certainly got the measure of cars like the Audi TT Roadster and the Mercedes SLK. The gearbox feels supremely meaty, the stubby lever encouraging you to flick up and down through the six gears just for the sheer tactility of the experience. Push harder and you'll be surprised at how much safe understeer BMW have built into the handling bias. It's certainly the antithesis of the tail-happy Honda S2000, erring more towards the benign Audi TT roadster in its feel at the limits of grip.

The Z4 2.5 models are hugely surprising cars. In terms of driving characteristics the Z4 is much like a BMW saloon, which to many will be praise indeed. The chassis and engines are supremely competent. It lacks a little of the outright edge of a true hairy-chested roadster but one suspects that for the majority of Z4 customers that's probably not a bad thing. The 2.5i looks decent value at £26,250 but there's a sizable £2,800 leap to get the extra 41bhp of the 2.5si, which some may deem too much. What's certain is that those looking for BMW's Achilles heel now have a much tougher task on their hands.

TOP 5 Z4 DEALS

The results below show the top Z4 deals on buyacar

	BMW Z4 2.5si SE 2dr Roadster Convertible
	ETR	Mthly	Saving £4,541	Price £23,899
	BMW Z4 2.5i SE 2dr Roadster Convertible
	ETR	Mthly	Saving £4,240	Price £21,460
	BMW Z4 2.5i Sport 2dr Roadster Convertible
	ETR	Mthly	Saving £4,518	Price £23,712
	BMW Z4 2.5i SE 2dr Auto Roadster Convertible
	ETR	Mthly	Saving £4,404	Price £22,791
	BMW Z4 2.5i Sport 2dr Auto Roadster Convertible
	ETR	Mthly	Saving £4,682	Price £25,043