BMW Alpina B4 vs BMW M4

What's the difference?

You could almost call the B4 S the anti-M4. It's still fast and practical but from a completely different perspective. It's much more a grand tourer than the M4 and even with the Akrapovic exhaust (usually a byword for joyous, anti-social racket), subtle.

For some, the price won't matter because the Alpina delivers what they want - M4-like straight line performance without the histrionics or the uncompromising chassis. And there's also a bit of that perverse exclusivity of the styling that you won't get anywhere else.

We cannot think of a faster or more invigorating four-seater luxury convertible for the money than the new M4 Competition.

Finally, after years of devastatingly fast droptops with remote steering and an unforgiving ride, the G83 generation discovers refinement and sophistication to go with its supersonic speed.

There’s terrific talent on tap here that no rival can even come close to right now. BMW is on a roll and this is the first M4 convertible that can sit proudly alongside the best of its classic M3 ancestors.

Alpina has always had a particular aesthetic that could uncharitably be termed as mid-'80s West German - all set square angles and body graphics. Think David Hasselhoff's Berlin Wall look. The company has never really deviated from adding squared-off body bits to the various BMWs it has rebadged under its long-running agreement.

For the B4S, Alpina adds the signature billion-spoke alloy wheels (only a slight exaggeration), a new front splitter complete with Alpina lettering, a weirdly proportioned boot lid lip spoiler and - not even joking - pinstripes. Like I said, mid-'80s West German. You can still recognise the sleek 4 Series Coupe but perhaps the worst of it is the super-sized, wonky-looking ALPINA B4S on the boot.

Inside is rather more restrained apart from the ill-fitting Alpina plaque under the climate control. Again, it's all 4 Series in here, with the lovely Merino leather liberally applied across the cabin. Less lovely is the wood on the door pulls and console but the door cards have an oddly appealing woven leather which looks and feels good.

Sadly the standard 4 Series steering wheel is along for the ride. There's nothing wrong with it - although the Alpina logo does look out of place - but if I were a product planner, I'd beg for the lovelier M wheel.

Hallelujah! The unloved folding hardtop is history and fabric is back in fashion in a BMW 3/4 Series-based convertible for the first time since the demise of the E46 convertible in 2006.

It improves the proportions and aesthetics out of sight while remaining superbly insulated. It’s also 40 per cent lighter to boot while liberating 80 litres of extra luggage space.

The roof requires just 18 seconds to drop away or erect again, and can be done so at speeds of up to 50km/h. And it looks great, with a taut fit that suits the BMW’s lithe lines to a tee. With all four windows dropped, it also does a fab impression of an American-style pillarless hardtop.

Roof up or down, the M4’s muscular styling has a tense sparseness to it that means business, reinforced by that oversized, M-specific kidney grille treatment that, admittedly, isn’t as divisive in real life. The smiley LED light wave out back also brings a friendlier tone, harmonising handsomely with the rest of the car.

This is probably the best-looking BMW convertible since the beautiful E46 era.

If you're in the front, you're in luck - it's a comfortable place to be, with plenty of leg and headroom. Down back isn't terrible despite the coupe roofline. The two seats are nicely shaped for maximum comfort and separated by an odd plastic tray. The fold-down armrest has two cupholders.

Front seat passengers score a pair of cupholders (bring the total to four for the car) and the long doors will hold a bottle each.

The boot swallows a reasonable 445 litres, which isn't at all bad.

The M4 Convertible is not a paragon of space efficiency, given its footprint.

At nearly 4.8 metres long and 1.9m wide, the M4 Convertible casts a sizeable shadow on the road, which only really pays dividends for front-seat occupants inside.

Ours was fitted with a very handsome pair of $7500, two-tone M Carbon bucket seats up front, a sort of futuristic tombstone design with a fixed headrest that looks like they were created by and for Stormtroopers; they do provide all the electronic adjustability one would need in terms of fore/aft, up/down and lumbar support movement.

But, unless you really need their g-force-bracing support and love their outrageous appearance, they are monumentally obstructive to effortless entry/egress and overall hip comfort if you don’t possess a gymnast’s physique. In fact, at times, they can feel downright torturous, especially in the gusset area due to the pointless (ironically) hard central bulge bit. The standard front seat set-up is perfectly fine, offering all the comfort and support expected in a luxury convertible, with the added bonus of headrest adjustability.

As with all G20/G80 generation 3/4 Series, the M4’s interior is a welcome return to form for BMW, from the excellent driving position and superb build quality, to thoughtful switchgear placement, brilliant ventilation and ample storage. And iDrive is probably the best and most intuitive multimedia system out there, too, needing no special skill or distraction once mastered.

A quick note about the instrumentation. The 4 Series design digital readouts are prettier than the standard 3 Series' ugly standard screen that looks ex-Honda Civic. This one offers alternative views and is easy to read at a glance. But it still makes us pine for good old analogue dials. Remember when BMWs were the world leaders in dial design?

Some familiarisation is also required to figure out the M part of the M4, including the various driving and performance modes; they’re divided into Road, Sport and Track settings. Yet, thankfully, they’re all far simpler to get your head round than before, which required too much fiddly concentration, since – once quickly learnt – everything is possible with eyes-on-the-road promptness. A new M Mode button offers pre-determined shortcuts to whichever drive combinations are desired.

The roof is well insulated, meaning that previous-gen folding hardtop-owning prospective buyers shouldn’t be too sad about the fabric above their heads. On the go, front occupants can enjoy a variety of configurations, starting with snug coupe-style cosiness and security, moving to cool pillarless hardtop-style windows-only down cruising, to the full top-down convertible glory. The latter also brings minimal buffeting at speed unless you’re stuck out in the back. Roof-up vision isn't brilliant, though.

Strangely, with the M Carbon bucket seat options ticked, it’s actually easier for some people to get into the back than the front. Pulling a strap sees the front bucket seats (slowly) whir as far forward as possible to allow sufficient room for people to clamber onto the rear seats.

Once sat, it’s clear that longer-legged people will struggle. Knee room is OK (especially if the front occupants are feeling sympathetic by moving their seats forward), there’s surprisingly adequate head room for your 178cm tester when slightly slouched, big feet can be tucked beneath the front seats and scalps never have to touch the rear glass thankfully.

And at least BMW has tried to make life back there comfier for smaller people, due to rear-facing air vents with climate and directional control, two USB-C ports, a pair of cupholders, a centre armrest and some handy storage. The materials are of a high quality construction, too.

However, the fixed back rest is far too upright, the knees-up posture quickly gets tiresome, the cushion is firm and you’re sat on a slight angle pointing outwards. Claustrophobics won't be too happy either. Annoyingly there aren’t side window buttons either, meaning only the driver can lower or raise them. The two-seater back seat is best saved for short trips or kids.

Happily, once the roof is dropped, the hemmed-in feel vanishes, there’s not too much wind intrusion or buffeting with the side windows up and there’s a sense of shared freedom that only a four-seater convertible can bring. Going the full drop-top experience will ruffle more than hairdos at freeway speeds, though. An optional wind deflector can fix that issue for front-seat occupants, but it goes over the back seats, turning the M4 into a two-seater ragtop.

Further back, the 300-litre boot isn’t accessible from the cabin, meaning you can’t put much inside at all. BMW fits a hinged flap that needs to be down for the roof to work since it cordons off the roof storage part of the boot when folded in; when lifted, there’s a useful amount of space for luggage, and it’s a handy rectangular shape instead of an L-shaped slot, but obviously at the cost of convertible driving. You can’t have both.

Note that, compared to the previous folding-hardtop M4, this boot is some 80L larger. 

There’s only one M4 Convertible available, in Competition M xDrive guise, and it’s not lacking for much.

We’re looking at a 375kW/650Nm 3.0-litre twin-turbo in-line petrol six-powered four-seater AWD ragtop capable of 0-100km/ in 3.7 seconds, on the way to either a 250km/h or optional 280km/h top speed, if your wallet allows. All from $176,900 before on-road costs. BMW’s serious here.

Standard features include an active M differential, adaptive suspension with auto levelling, an M Compound Brake package and selectable driving modes, underlining the M4's driver focus.

You'll also find leather upholstery, head-up display, adaptive cruise control with full stop/go functionality, automatic parking assist, a surround-view camera, a lap timer and “drift analyser”, paddle shifters, wireless smartphone integration including Apple CarPlay/Android Auto connectivity, emergency services access, three-zone climate control, electric front seats with memory, front seat heaters, ‘air collar’ neck warmer, keyless entry/start with BMW Digital Key, key fob control for windows, roof and boot opening, split-fold rear backrest, M carbon fibre trim, leather steering wheel, a 12.3-inch instrument display, a 10.2-inch control display, 16-speaker Harman/Kardon surround-sound audio system, digital radio, MP3 player, cloud-based satellite navigation, trip computer, wireless charging, ‘Hey, BMW’ assistant, outside connected services assistance, ambient lighting, BMW LED Laserlight auto high beams with active cornering and light sensitivity, rain-sensing wipers, electric heated/folding exterior mirrors, tyre pressure monitors, 19-inch front/20-inch rear wheels/tyres and a tyre repair kit.

Taking care of safety are six airbags, forward collision warning, Autonomous Emergency Braking (AEB) front and rear, with front/rear cross traffic alert, lane departure warning with passive steer assist, lane keep with active assist, blind spot monitor, 360-degree view cameras, parking assist, parking sensors, anti-lock brakes with electronic brake-force distribution and brake assist, stability control, traction control and corner braking, among other features. More details in the safety section below.

Our BMW also included three options that detracted from the M4’s comfort and/or taste: $5000 Frozen Portimao Blue paintwork, $7500 M carbon bucket seats and $8500 M Carbon exterior package, upping the total unnecessarily to $197,900 before ORC.

Rivals in the 2+2-seater ragtop arena are few and far between. With no Audi RS5 Cabriolet in existence, Audi only has the S5 Cabriolet from $126,200, but that’s up against BMW’s M440i Convertible from $135,900. There’s more parity with the ageing Mercedes-AMG C 63S Cabrio from $202,177 and softer Lexus LC 500 Convertible from $213,877, while the cheapest Porsche 911 Carrera Cabrio will set you back a cool $262,900.

Seen in that light, it’s fair to say the standard M4 Competition xDrive is in a league of its own – particularly when you factor in the BMW’s ability to more-or-less equal and even exceed the others at their own game. And that’s something the previous version could not achieve.

So, that’s a surprising yes for value.

A lot of your extra money turns up under the bonnet. These days the 440i packs BMW's slick B58 turbo straight six and the B4S does likewise. The boys from Buchloe in Bavaria (there are certain to be women there, too, I just liked the alliteration) added a pair of Alpina-spec turbos to generate a whopping 324kW and, more importantly, 660Nm. Alpina says 600Nm (the max torque figure of the brilliant M4 CS) is available from 2000-5000rpm, while the full 660Nm is available from 3000 to 4500rpm.

The M4 Pure has 317kW and 550Nm from the S55 straight-six. Just so you know.

Like the 440i but unlike the M4, the B4S employs the dependably brilliant eight-speed ZF automatic found throughout the BMW range.

Here is a summary of Australian-market outputs and prices for the M3 and M4 convertible autos, with the prices in brackets being approximate inflation-adjusted figures for today.

1999 E36: 236kW/350Nm 3.2L in-line six-cylinder engine (I6), $152,000 ($266,000 in 2022); 2003 E46: 252kW/365Nm 3.2L I6, $158,000 ($240,000); 2008 E93: 309kW/400Nm 4.0L V8, $183,442 ($240,000); 2014 F83: 317kW/550Nm 3.0L twin-turbo I6, $178,430 ($202,000).  

In 2022, the G83 M4 Competition lives up to its name in more ways than one, with a 2993cc 3.0-litre double overhead cam direct-injection twin-turbo I6 known as the S58 series, which is itself derived from BMW’s B58 modular family of engines. Its 375kW is delivered at a lofty 6250rpm, while there’s a 650Nm plateau of torque between 2750rpm and 5500rpm.

A kerb weight of 1920kg means the M4’s power to weight ratio is an impressive 195.3kW/tonne, helping its published 0-100km/h time of 3.7s. For a few grand extra, the company will up the top speed by 30km/h, to 280km/h.

BMW says the engine includes cooling and oil supply systems designed for extreme lateral forces at high speeds, while the exhaust uses electrically controlled flaps for a more raucous noise.

Power is channelled to all four wheels continuously via an eight-speed M Steptronic transmission with a trio of shift programs. The AWD system features an active differential to better transmit torque to all four wheels, while drivers can choose one of three, progressively more rear-wheel drive (RWD) biased modes: 4WD, 4WD Sport and 2WD – the latter being a pure RWD set-up.

Other related changes the M4 boasts over regular 4 Series models include special stability and traction control tuning, a double-joint spring strut front axle with unique axle geometry and variable-ratio steering, a five-link rear axle featuring its own kinematics and elastokinematics, M-specific adaptive dampers, a configurable braking set-up according to feel and response, and forged M light-alloy 19-inch alloys up front and 20-inch items out back.

Choosing the AWD-only convertible over the equivalent AWD coupe adds 145kg (and 195kg compared to the RWD coupe), though this is partly offset in two ways over the preceding, folding-hardtop M4 Convertible: firstly, using the soft top drops weight by 80kg; and secondly, while the AWD system does add 50kg, it’s at a lower centre of gravity, thus naturally improving vehicle dynamics.

Which are electrifying, by the way.

Alpina quotes 7.9L/100km on the combined cycle and we went through the premium unleaded at the rate of 11.7L/100km. I enjoyed myself, so that's not a terrible result.

We managed 12.1 litres per 100km in a mixture of urban, freeway and rural-road driving, including plenty of performance testing. This is a two-tonne M4 convertible capable of supercar speeds, after all. In that context, the economy is more than acceptable. No doubt the stop/start engine function (at idle) helps here.

For the record, the official combined-average claim for this Euro 6-rated BMW is 10.4L/100km, for a carbon dioxide emissions average of 237 grams/km. Thanks to a fuel tank that holds 59 litres of 98 RON premium unleaded petrol, it can manage an average of almost 570km between refills.

One of the key differences between the B4 and M4 is the ride. While the M4 can crash over bumps and generally be a little hard to live with, the crew in Buchloe have gone after a much more plush ride. And in that they have succeeded because the B4 S is a mighty fine cruiser. Bumps are dismissed with a haughty disdain, even Sport + silliness doesn't completely write-off ride quality.

Very impressive too, is the steering. While still not at Lotus Elise levels of feel (few cars are), the Alpina tweaks connect the your palms to the road with more clarity than what you'll find in the 440i or M4. Where the M4 particularly adds too much weight, the 440i is a bit more circumspect in that regard.

And then we come to the engine. The B58 six is a belter, better even than the N55 that preceded it. It's still a 3.0-litre straight six but is part of BMW's modular engine family that starts with a 1.5-litre triple in the Mini and 1 Series. The Alpina-spec turbos are noisier, the Akrapovic exhaust lighter and also noisier. It doesn't have the all-out crackle and pop of an Audi or Merc (perish the thought), but when you're on it, the B4 means business. The 660Nm of torque, available over a wide rev range, delivers a steel fist wrapped in a velvet glove and bubble wrap - the speed builds rapidly but smoothly. 

The approach to the chassis tune seems to be based on the driving talents of mere mortals on normal roads, which is kind of like the 440i. It's terrific fun to drive hard but it's very forgiving and patient. The great thing about it is that you wouldn't think twice about jumping in it for the long haul, so comfortable and quiet is the cabin. The M4 will leave it for dead on a winding road, but that's perfectly fine.

One irritant is the replacement of the admittedly cheap BMW gearshift paddles with weirdly non-tactile buttons. They're not particularly easy to use and, probably worse for a sporty car, unsatisfying. It's an odd detail with which to go off the reservation. Cheeringly, the eight-speed ZF is its usual perfect self, so you don't have to worry too much about manual mode or go old school and use the shifter.

Marvellously.

Earlier, we said that the previous M4 (and some earlier M3 generations) never hit the dizzy heights the best like the E46 managed.

The reason why is bandwidth. Not WiFi bandwidth, but rather the newfound breadth of capability that the G83 model has acquired.

Yes, while even the slowest examples of previous M3s and M4s remained thrilling, with blisteringly potent acceleration accompanied by a soaring exhaust soundtrack, the post-E46 models seemed to become almost too obsessed with the pursuit of performance. Thunderous V8s and twin-turbo V6s are all good and well, especially when they provide explosive responses, but there’s more to sports cars than sheer bloody-minded speed.

More specifically, though the handling and roadholding were outstanding, the previous M4’s steering didn’t feel as connected or one with the driver, instead seeming a little remote and detached. Conversely, even with adaptive dampers on offer, the suspension (on Australian roads) lacked sufficient isolation from bumps and thumps, and so was never settled or calm. It was all too nervous and edgy, like a drug-addled athlete who’s indulged in too much partying.

Thankfully, the curse is broken with the latest iteration, even in the heaviest and slowest version like our M4 Convertible as tested, pushing out boundaries to thrilling effect once more.

With the newly-simplified and logically presented M performance modes only a push of a button away, the driver now no-longer has to concentrate on what setting they’re in, and instead just immerse themselves in the experience of accelerating, steering, cornering, braking and controlling this incredible sports convertible.

Tremendously strong in regular Road mode, the M4’s performance certainly lives up to the legend, stepping up into the supercar realm when Sport or Track are chosen, hunkering down as it thrusts towards the horizon with relentless speed and determination, accompanied by the gorgeous twin-turbo six’s revs as they soar towards the red line. The ultra-alert eight-speed auto’s operation is equally seamless, displaying uncanny intuition in its selection of the right ratio at exactly the right time.

These are all incremental improvements over what has come before. But what’s really changed is how rock-solid the BMW feels as it belts along at speed, magnetised to the motorway regardless of weather, its new AWD engineering keeping everything steady and planted. No more tetchiness to unnerve the driver.

Which makes the feel and fluency of the chassis even more remarkable, given that now all four wheels are driven. The very opposite of leaden or inert, the superbly weighted steering is instead light and alive in your palms, as you carve through corners with pin-point precision. Some might find it a bit too eager to change direction at first, but we reckon BMW has judged the balance just right. Its sheer agility is as life-affirming for driving enthusiasts as it is immersive. Bravo, BMW.

With so much grip and control, this is not to say that the driver can’t hang the M4’s tail out every-which-way, since the chassis set-up allows for progressive oversteer, even in Road mode, along with as much drifting as your courage allows where safe. As with the best sports cars, the M4 is as steerable from the seat of your pants as it is using the throttle.

Finally, there’s the M Adaptive chassis tune, that at long last broadens the M4’s repertoire from motorway grand tourer and rural-road blaster to city slicker and urban warrior, thanks to the suspension’s ability to better-absorb a much wider array of terrible road surfaces. Comfort now lives up to its name, with the ride – though still firm – no longer hard or crashy around town, ushering in a new level of civility that won’t fatigue or aggravate you or your occupants. We're so happy to report this progress.

One area where BMW might want to keep improving, though, is the abundance of road noise intrusion over certain coarse chip bitumen. While easily muffled by the sweet sounds of the twin-turbo six, banging audio system or dropping the roof, it now seems more obvious that the rest of the car has smartened up so much.

A small fly in an otherwise hugely satisfying ointment.

There is no specific crash-test data for the BMW G83 M4 Convertible.

However, tested in 2021, the G23 4 Series Convertible it’s based on (and tested in European-spec 320d guise) managed to score a five-star ANCAP rating, and performed strongly across each of the main disciplines – adult protection, child protection, vulnerable road-user and safety assist categories, achieving 96 per cent, 86%, 93% and 73% respectively.

Standard safety features includes six airbags (a driver’s knee airbag, dual frontal, side chest and head-protecting airbags for the first row and side chest protecting airbags for the second row), forward collision warning, Autonomous Emergency Braking (AEB) front and rear, with front/rear cross traffic alert, lane departure warning with passive steer assist, lane keep with active assist, blind spot monitor, 360-degree view cameras, parking assist, parking sensors, anti-lock brakes with electronic brake-force distribution and brake assist, stability control, traction control, corner braking and tyre-pressure monitors, BMW LED Laserlight auto high beams with active cornering and light sensitivity and rain-sensing wipers.

The AEB technology is rated for City, Interurban and Vulnerable Road User, according to ANCAP, and works between 5km/h and 210km/h in daytime and nighttime conditions.

There are also two ISOFIX points as well as two top tethers for straps in the rear seats.

Alpina offers a two-year/unlimited-kilometre warranty which is a bit behind the times and not in keeping with the price point. Servicing is another matter altogether and you're subject to your dealer's standard charges for servicing.

We feel here is where the company drops the ball.

Trailing all of its main luxury car rivals (except Porsche) by two years, BMW only offers a three-year/unlimited kilometre warranty, as well as three years of roadside assistance.

BMW says its vehicles’ servicing is condition-based, depending on how they’re driven and other factors, with a dash warning appearing to let the driver/owner know when it’s time. We advise servicing your M4 annually or at every 10,000km, just to be sure.

No capped-price servicing system is offered. However, as long as the first one is paid for before the first service on a new vehicle, the ‘BMW Service Inclusive Basic packages’ is available at extra cost, covering scheduled servicing for three years/40,000km or five years/80,000km.

No prices are published for M models like the M4, but a normal 4 Series costs from $1800 for the five-year/80.000km package. You can bet an M4’s will cost more.