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BMW M135i xDrive vs Mercedes-AMG A45 S comparison

By Georg Kacher | Photos: Steffen Jahn, 01 Dec 2019 Car Comparisons

BMW M135i xDrive vs Mercedes-AMG A45 S comparison feature

Range-topping 1 Series takes on an A-class so over-drugged it even eclipses the V8-engined C63 AMG. Welcome to the new automotive world order

This is not your classic winner-takes-all comparison.

When you pit 225kW against 310kW, performance cannot be the sole decider, or this story would end right here. What we’re trying to find out instead is how the most potent compact hatchbacks available from BMW and Mercedes fare when you pull out all the stops.

To do so, numbers took second priority to subjective impressions. The stopwatch was replaced by the body clock, the shameful filling station receipts were binned with an impish grin, and our driving licences were left soaking overnight in holy water. After a longish wait, it’s at last crunch time for the Mercedes-AMG A45 S on home turf, with a blue BMW M135i looming large in the rear-view mirror.

The Benz welcomes the front seat passengers with one-size-fits-all bucket seats. To set the tone for the day, we dial in Sport Plus and summon the gaudy Supersport display with its big fat gear indicator and speedometer circled by a rainbow rev counter that in turn is flanked by two busy bar graphs.

AMG has also included a Race Start function, but only if you lift your left foot off the brake within three seconds while keeping the right hoof planted, and easily drowning every rump-ta-ta band is the blaring Real Performance Sound processor.

MOTOR review: AMG A45 S first drive

But all this ballyhoo is merely a prelude to the great dog-and-pony show known as Drift Mode, which can only be locked in with the transmission in manual, the drive program in Race and ESP switched off – and then you must pull both shift paddles simultaneously, then confirm powerslide mode by a quick flick of the Up paddle.

Sitting alongside the matte-grey Benz, waiting for the thumbs up and impatiently wow-wowing against the limiter, is the M135i, also with one twin-scroll turbo, four cylinders, eight gears and four driven wheels. It delivers 450Nm through its automatic transmission – versus 500Nm and dual-clutch in the Benz – though in launch control mode the BMW’s maximum torque is also available in first and second gears. Part of the upgraded xDrive system is a Torsen diff lock that keeps the front wheels in check.

We would also like you to welcome an all-new and highly effective electronic feature dubbed ‘actuator contiguous wheel slip limitation’, or ARB. Borrowed from the i3 (yes, really), ARB controls wheelspin inside the black box, and bypassing the DSC module speeds up the felt response time tenfold, thereby nipping understeer in the bud.

Sounds unreal and feels unreal. Although the intervention of traction control can be reduced and eliminated in two steps, the xDrive system retains its pre-set 50:50 torque split at all times rather than ever allowing the rear wheels to pick up the lion’s share of the momentum.

The BMW is marginally quicker off the mark, but its first gear is shorter, and as soon as the AMG engine has picked up enough revs, the kick-in-the-butt DCT and fast-growing extra momentum urges the A45 S forward.

Just for the record, the 0-100km/h duel sees Swabia beat Bavaria 3.9 to 4.8sec. As we expected, that’s an impressive victory for the Benz, which throws in a bit of drama for good measure – like a shrill take-off chirp, an increasingly upbeat soundtrack that changes from angry to indignant around 4000rpm, an artificially induced lift-off blat-blat, and the reluctance to shift up into third just in case the fun is not yet over.

In contrast to the A45, the new M135i is anything but an evolution of its predecessor. While the coveted previous model was tail-happy, all over the place when pushed, constantly struggling for traction in the wet, the all-new model trades rowdiness for poise, sideways antics for precision, hooliganism for manners. In other words, it doesn’t really compare.

Sadly, even the currently most powerful BMW four-cylinder engine is two pots, 25kW, 50Nm and four-tenths short of the deceased M140i straight-six we loved to bits. But it is what it is, and if you really want to beat the AMG A45 S at its own go-faster game, the only option for BMW aficionados is the much rawer and even more involving rear-drive M2 Competition.

Both these contenders are easy to drive fast. Grip, traction and roadholding are on a similar level, way above the pack, and despite the gain in power and grunt, the limit is more accessible now.

Bespoilered, with LED slit eyes and bad-boy Panamericana grille, the A45 S is dressed to match its expressively aggressive mindset. The BMW comes with a bespoke M Sport body kit, lowered suspension and low-profile, 18-inch tyres (Oz-spec cars get 19s), but despite the extra street-cred it’s closer to the base 118i than the AMG-prepared A-Class is to the A160.

Fitted to the Benz is the world’s most powerful volume-production four-cylinder engine outside the sports car realm. Even the base unit rated at 285kW is a milestone effort, but the S version churns out an even more mind-boggling 310kW at 6750rpm. In combination with the machinegun-rapid gearbox and trick AWD system, this exceptional kraftwerk will swiftly propel the 1550kg crackerjack to a top speed of 272km/h.

Smartness and refinement characterise the M135i. The most involving new 1 Series model is above all a subtle and discreet master of the winding road. No steering fight? You bet. Not a trace of understeer?

Take my word for it. What does the trick is the latest software, which coordinates the interplay between man and machine more effectively and more quickly. It invites you to straddle the limit, which happens to be more malleable and easily negotiable in the admirably adaptive M135i than in the more hardcore Mercedes. 

To lift their M Sport effort to the next level in the handling, roadholding and performance stakes, the BMW engineers made sure the steering was quick yet superbly grounded, nicely progressive and well weighted. Other virtues include the electronically enhanced, near-neutral cornering balance, firm tyre grip and – within confines – needs-based torque distribution that keeps the palms of the driver informed without irritation.

Downsides? Even in Comfort, the ride is relatively unsettled. Sport doesn’t hit the bullseye either, because the now exaggerated vertical articulation is often at odds with the more brusque response to high-frequency irritations.

The Mercedes does better than that. Its suspension is unexpectedly compliant in Comfort, still cushier than the M135i in Sport, and better tied down in Sport Plus and Race. It also responds more impatiently to throttle orders, builds up revs more eagerly and hangs on to the power with unabashed vigour.

When invited to do so, the tail swings round in a creamy arc, and as long as the driver maintains the tighter-than-regular steering angle and the punchier-than-normal torque flow, the winged five-door hatch performs as closely to a pedigree drift machine, as it can, from entry to exit.

The secret behind this on-demand change of handling attitude is known as AMG Torque Control, with electronically controlled multi-disc clutches on each side of the rear differential, one for each driveshaft.

In combination with the fully variable electro-mechanical front-to-rear torque split, this fully variable rear side-to-side torque distribution ensures optimum traction in all weather and road conditions – except in Drift Mode, when the outer rear wheel is fed all the oomph it needs while the inner wheel takes time off.

The challenging ergonomics to tap these wide-ranging talents involves a selection of hard keys, a large touchpad and a multi-function steering wheel complete with several sub-menus and multiple redundancies. In a nutshell, the AMG A45 comes equipped with three scalable dynamic interfaces: Level One defines the 4Matic set-up. With the AMG Dynamics menu in Basic or Advanced, AWD works in Comfort mode. Upgrade to Plus or Master and Sport mode will automatically take over.

Level Two offers three different ESP activities: On, Sport handling mode and Off. Level Three lets you choose from six different driving programs labelled Ice, Comfort, Sport, Sport Plus, Race and Individual. The associated software controls all drivetrain-related functions such as throttle response, shift points and speed, sound processor, and exhaust note in Reduced, Moderate, Sport or Dynamic fashion.

Other flexible tools are the available adjustable dampers, active torque split, ESP calibration and steering action. Devoid only of air suspension and rear-wheel steering, the supersonic A-Class is about as close as a compact car can possibly get to total high-tech overkill.

The M135i is a carver, not a scrubber. As soon as you turn the wheel and start reeling in the apex, it assumes a relatively flat stance. There is no dedicated drift mode, and the good old handbrake has of course long been replaced by an electric push-button device, but the combination of abrupt lift-off and simultaneous hard turn-in induces a mild four-wheel slide that won’t last, at least not in the dry.

Try harder still and chances are you’re overdriving the car, which looks silly and is certainly less rewarding than to let steering, throttle and chassis sort things out with cool competence and utmost efficiency.

Even when you deliberately overstep the mark, this BMW will sort itself out, tighten or relax the line, suggest additional input or substitute for it. It goes where you point it, fusing accelerator position and steering angle to the fastest physically possible vector graph.

Boring perfection? Not at all. Instead, this is a compelling fusion of entertaining handling and easily accessible performance, even on tricky backroads.

Out in the open, the preferred AMG attack mode is the DNA in Sport Plus, Dynamics in Master, adaptive dampers in Sport and transmission in Manual. In built-up areas, though, it’s back into Drive, which does a fine job holding the appropriate gear, shifting down just in time, keeping the noise below the foul eggs threshold and only making full use of all 7000rpm (the BMW is redlined at 6000rpm) when opportunity knocks. The Sport Handling program encourages the odd lift-off tail-wagging antics and a momentary trace of exit oversteer.

At speeds of up to 120km/h, the standard steel brakes have no problem reeling the A45 in reliably and in fade-free fashion. The same is true for the BMW, which evinces reassuring stopping power and easy modularity. Both electro-mechanical rack-and-pinion steering systems are of the variable-effort and variable-rate kind.

Just as BMW promised zero understeer or torque steer in the new M135i – and has impressively delivered – Mercedes claimed a totally neutral handling attitude and no steering fight with the AMG A45 S. With an extra 85kW and despite its wider footwear, though, the AMG will understeer slightly at the limit, except in drift mode of course.

Stepping into the BMW, the controls feel initially less connected, the response less sharp, the overall character more GT-like than emphatically sporty. But it doesn’t take more than a dozen kays before this grand scheme of calibrations is again totally in line with a beefed-up 1 Series that is clearly more 135i than M.

In a way, the BMW has a different character than suggested by its badge. After all, the rear-drive M240i is more M than this top-of-the-line, all-wheel drive 1 Series and, despite the A45’s sparkling cocktail of abilities, the defunct M140i simply refuses to disappear from the back of my mind.

Would I spend my own money on the hottest or the second-hottest hatch on the market? Probably not, but then this type of transportation is out of tune with an older person tired of getting clobbered for playing hard with overly conspicuous toys. A more user-friendly AMG A45 S wagon or M340i xDrive wagon would seem as dynamically appealing as these cramped hatches.

Generally speaking, I would struggle putting down this sort of money for any slick and quick metamorphosis of an entry-level motor car. The lower door panels of the Benz are for instance made of low-rent, rock-hard plastic, the BMW interior sports a disturbing mix of real and fake brightwork, rear seat leg and headroom is a bad joke in both combatants, and the bulk of those gadgets and the schoolmasterly ergonomics do absolutely nothing to stimulate the friendship.

A case of less is more? It depends. But a whiff of electrification would help appease the nerdy Greta Thunberg inside.

All about the drive on MOTOR reviews

Fast Facts

  Mercedes-AMG A45 S BMW M135i xDrive
Body 5-door, 5-seat hatchback
Drive all-wheel
Engine 1991cc inline-4, DOHC, 16v, turbo 1998cc inline-4, DOHC, 16v, turbo
Bore x Stroke 83.0 x 92.0mm 94.6 x 82.0mm
Compression 9.0:1 9.5:1
Power 310kW @ 6750rpm 225kW @ 5000-6250rpm
Torque 500Nm @ 5000-5250rpm 450Nm @ 1750-4500rpm
Power/Weight 200kW/tonne 148kW/tonne
Transmission 8-speed dual-clutch 8-speed automatic
Weight (dry) 1550kg 1525kg 
Suspension (f) struts, coil springs, adaptive dampers, anti-roll bar struts, coil springs, dampers, anti-roll bar
Suspension (r) multi-links, coil springs adaptive dampers, anti-roll bar multi-links, coil springs, dampers, anti-roll bar
L/W/h 4445/1850/1412mm 4319/1799/1434mm
Wheelbase 2729mm 2670mm
Tracks 1597/1558mm (f/r) 1560/1563mm (f/r)
Steering electrically assisted rack-and-pinion
Brakes (f) 360mm ventilated discs, 6-piston calipers 360mm ventilated discs, 4-piston calipers
Brakes (r) 30mm ventilated discs, single-piston calipers
Wheels 19.0 x 8.5-inch (f/r) 18.0 x 8.0-inch (f/r)
Tyre Sizes 245/35 ZR19 (f/r) 225/40 R18 (f/r)
Tyres Michelin Pilot Sport 4 S Michelin Pilot Super Sport
Price $90,000 (est) $63,990
Pros Performance; handling; traction; ride Balance; brakes; grip; electronics
Cons Complication; interior plastics/space Styling; interior trim/space; it’s no M140i
Rating 4.5 out of 5 stars 3.5 out of 5 stars

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