BMW 4 Series Convertible Review: 420d Diesel, 428i And 435i Petrol

Karl Peskett | 3 Comments

BMW 4 SERIES CONVERTIBLE REVIEW

What’s Hot: Delectable drivetrains, great steering, suspension tune 'right' for Aussie roads
What’s Not: Extra weight blunts performance, cramped rear
X-FACTOR: Drive it hard or cruise in style - a drop-top that, on road, feels as good as it looks

Vehicle Style: Premium medium convertible
Price: $88,800 (420d), $97,500 (428i), $126,600 (435i)
Engine/trans:
420d: 2.0-litre 135kW/380Nm 4cyl diesel | 8spd
428i: 2.0-litre 180kW/350Nm 4cyl petrol | 8spd
435i: 3.0-litre 225kW/400Nm 6cyl petrol | 8spd
Fuel Economy l/100km (listed): 4.8 l/100km (420d), (428i): 7.7 l/100km (435i)

OVERVIEW

Creating a convertible is never as simple as lopping the top off a coupe. Do that and suddenly the chassis stiffness goes out the window.

With the new 4 Series Convertible, BMW has two huge struts integrated into the underside to get the bracing right for a nice rigid chassis.

There's a downside of course: a weight penalty. But you'd hardly know.

BMW says that it opted for a hard top to maintain the striking coupe style of the 4 Series, plus it helps keep the coefficient of drag really low (0.28 with the roof up).

And it not only transforms quickly from coupe to convertible, you can do it at speeds of up to 18kmh. Which means you won’t have to stress if the lights go green halfway through putting the roof up (or down).

So has the extra 240kg dulled the 4 Series experience?

BMW invited us to experience the wind in our (almost absent) hair to find out what each variant was like.

Here’s how it went.

THE INTERIOR

  • Sat nav, dual-zone climate control, keyless entry and ignition, cruise control, multi-function steering wheel.
  • Powered front seats (435i), manual front seats (420d, 428i), rear air-vents
  • iDrive with voice control, Bluetooth audio and telephony, on-board music HDD storage.
  • Three piece convertible roof, with lift-function for ease of storage, 20 seconds movement up to 18kmh.
  • Wind blocker mounts behind front seats

With an interior lifted straight from the impressive 4 Series Coupe, the Convertible is a familiar (and nice) place to be.

That means the same swoopy dash intersected by aluminium trim, clear, precise instrumentation and hip-hugging seats with excellent support.

The steering wheel in the 420d and 428i is lifted straight from the 3 Series, but the 435i gets the wonderful M steering wheel with smoother leather, thicker rim and more padding - one of the best in the business.

Convertibles traditionally lose out on practicality - after all, the roof has to be stowed somewhere.

It's not so bad here. With the roof up, there’s 370 litres of space and 220 with it stowed. But there’s also a big rectangular port behind the rear seats for longer pass-through items (like a surfboard or skis, for example) .

A button on the boot's interior allows the boot-lid to separate and the whole roof assembly lifts up enough to allow items to be easily fed through the gap.

Press the 'down' arrow and the mechanism lowers the collapsed roof and puts the bootlid back in place. Handy.

Despite the skin being different, and a few tweaks to the strength of the controlling actuators, the roof mechanism is effectively a carry-over from the previous 3 Series Convertible.

In essence, if you’ve seen its roof in action, then you’ve seen this one. Movement is quite fluid, and it’s all done in 20 seconds, four seconds faster than the previous 3 Series.

Lastly, BMW's work on aerodynamics has clearly paid off. You can comfortably have a conversation with the roof down at the national limit. Raise all four windows and you could even call it quiet.

With the roof in place, it's just like a coupe - it's impressively hushed.

ON THE ROAD

  • 135kW/380Nm diesel | 180kW/350Nm petrol | 225kW/400Nm petrol
  • 8spd automatic with paddle shifters across the range
  • Rear-wheel-drive
  • 0-100kmh: 8.2s (420d), 6.4s (428i), 5.5s (435i)
  • Aluminium double-joint spring strut front | Five-link multilink rear
  • Electric power steering (420d, 428i) | Variable sport steering (435i)

Our time began with the 420d, and immediately, the chatter of a diesel engine is more apparent than you'll notice in the coupe.

Start moving though, and the rustle of wind and light road noise from the 45-profile tyres start to mask the diesel sound.

The automatic teams well with the 2.0-litre oiler, softly dropping each ratio into the thick of the torque curve, but because it weighs so much more than the Coupe, the turbo lag is magnified.

Even in Sport mode, there's quite a pause when accelerating out of a corner. You can counter this partly by employing the paddles behind the wheel, taking manual control, but it only eliminates some of the lag.

This variant is certainly a cruiser; ride the wave of low down torque and enjoy the smooth shifting transmission. With just 4.8 l/100km combined fuel use, the benefit is low emissions.

Like most BMWs, steering feel and weight is exceptional, feeling every bit like the 3 and 4 Series, and the suspension is pliable enough to prevent crashing and thumping.

It's still a heavy car, however, so at ten-tenths, it starts to scrub. But, really, pushing it to its limits is kind of missing the point of a diesel convertible.

Despite its lower price, BMW says that the 420d is on equal terms with the 435i for sales figures. The volume mover is the 428i, the car we hopped into next.

Jumping into a petrol 2.0-litre straight after a diesel is a revelation, especially one that is good for 180kW and 350Nm.

The extra urgency and lack of lag is immediately apparent, with the shift into Sport mode bringing virtually instant response. With a 0-100kmh time of 6.4 seconds, the 428i’s power feels much more suited to the car’s character.

With the roof down, there is an excellent blend of four-cylinder induction noise up front and exhaust note from behind. It's no zinging six (that would come later) but the sound for a four-banger is very good.

Again, the steering is superb, and it's noticeably lighter, perhaps due to a little less weight over the front wheels.

The ride is also very good, with enough compliance to smooth off most of the hard edges of bumps and with good rebound control that stops the body jostling around.

Because it's lighter, it's more 'chuckable' than the diesel; its drivetrain also lending itself to a more spirited drive.

But if it's an all-out thrash you want, and you have to have a droptop, then you can't go past the 435i Convertible.

With its sublime six which sings to the heavens with a hearty metallic scream, it'll sprint to triple figures in 5.5 seconds. Dropping the roof only adds to its aural appeal, with a throaty exhaust note and a delectable induction howl.

In Sport mode, the auto is sharper again than the other variants, and with eight-speeds to play with, it rapidly piles on speed in an urgent linear fashion.

With the bigger motor it is more nose-heavy, but has the advantage of plenty of grunt - 225kW and 400Nm to be precise.

That means any understeer scrub can be dialled out by plenty of right foot encouragement. And in Sport+ there's enough freedom from the stability control to fix up the errant front end with some rear slip.

Perhaps, if we were to put this car and the Coupe in a 'face-off' around a mountain road, the convertible would lose out to the 435i Coupe - but there is certainly little in it.

Like the Coupe, the 435i Convertible is a superb driver's car, despite the extra 240kg it's lugging around.

On those beautiful 19-inch M-sport wheels, be prepared for quite a bit of road noise. And behind the wheels, you'll find blue-calipered M-spec brakes, which feel fantastic at all speeds.

The suspension as standard on the 435i is the adaptive M suspension, which brings a much firmer ride than we experienced in the other two variants. The flip side is very good handling for a metal-topped convertible.

Match that with excellent steering and you have a droptop that is actually very good to drive.

The real question remains, though: is it stiff enough with all that extra bracing? You betcha.

Though there’s a slight shimmy from the windscreen if you’re on a really, really bad road, it’s hardly noticeable. And with the roof up, it’s as solid as a rock.

SAFETY

ANCAP rating: The 4 Series range hasn’t yet been tested by ANCAP or EuroNCAP.

Safety features: Front and side airbags for front passengers, pop-up rollover protection behind rear seats, DSC with ABS and traction control, Cornering brake control, Brake fade compensation, Brake assist.

TMR VERDICT | OVERALL

While the E-Class Cabriolet and the Audi A5 Cabriolet are nicely made vehicles, the bland drive they offer means the 4 Series sets the benchmark for fun, droptop motoring.

And that’s despite it being saddled with a metal roof.

The 4 Series Convertible feels great on the road - whichever model you choose. At the wheel, it gives you feedback galore, feels rock-solid even on ratty tarmac, and has a choice of three simply beautiful engines under the bonnet.

Of the three we tested, it’s a difficult pick a winner here. Each has its own character and is a profoundly enjoyable drive.

The head says go with the cheaper 428i - although, at near $100k, it's hardly cheap - while the heart leans to the punchy 435i, despite its $126,600 price tag.

Either way, BMW’s 4 Series Convertible is a very enjoyable way to get some sun(burn).

MORE: BMW 4 Series Convertible: Price and Features
MORE: BMW 4 Series Convertible Revealed

MORE: BMW 4 Series Coupe: Price and Features

Pricing (excludes on-road costs)

  • BMW 420d Convertible - $88,800
  • BMW 428i Convertible - $97,500
  • BMW 435i Convertible - $126,600

Filed under: Featured, review, BMW, petrol, convertible, diesel, rwd, automatic, sport, performance, prestige, lifestyle, medium, Advice, special-featured, enthusiast, 6cyl, 4cyl, 2door, bmw 4 series, 8a, bmw 4 series convertible, 4seat, available, 85-90k, 95-100k, 2014my, 125-150k, 2014 march launch

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  • Mike says,
    6 months ago
    I just cannot fathom why a more powerful engine and a few extra features can add 40k to the entry level model. Ripping off Aussies as usual.
  • Anton says,
    6 months ago
    I thought drive-away prices have to be published.
    • Mike Stevens
      Mike Stevens [TMR] says,
      6 months ago
      Hi Anton,

      Not at all. It's not a matter of TMR choosing not to publish drive-away prices, it is simply that they vary from state to state and dealer to dealer. Sometimes carmakers will specify a drive-away deal, but as a general rule, prices are listed as "Manufacturer's List Price". This essentially means price from factory, plus dealer markup if any, and various costs and charges applied depending on area, state fees, etc.

      Cheers.

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