BMW 6-Series (E63)

Debut: 2004
Maker: BMW
Predecessor: 6-Series E24

The original BMW 6-Series was a beautiful coupe. Involving to drive, comfortable to ride and desirable to own, it was the symbol of BMW coupes. Unfortunately, in 1990 BMW replaced it with the 8-Series, which was bigger, bulkier, more expensive and less inspiring to drive. The 8-Series didn’t repeat the sales success of its predecessor and was killed early. Since then BMW have not produced any coupes beyond the 3-series coupe, what a pity.

In late 2003, the 6-Series was reborn. It was derived from the 5-Series platform and componentry, having its own (shortened) chassis and clothed with another controversial design by Chris Bangle. Like the 5-Series, the chassis is an aluminum-steel hybrid. In order to shift weight towards the rear to benefit handling, the front chassis frames, engine-mounted sub-frame and bonnet are made of aluminum while the center to rear chassis is steel monocoque. Further weight saving is made by thermoplastic front fenders, composite boot lid, aluminum doors and aluminum suspensions. Even installed with a 4.4-litre V8, the new 645Ci is just 50kg heavier than the 3.5-litre 6-cylinder M635CSi of the past. That’s impressive by today’s standard.

The Bangle design is inevitably strange, but it is already more conventional than the 5-Series and Z4. Its smooth-flowing profile enables a low drag coefficient of 0.29 and is easy to eyes. Although the headlamps and grilles still look odd, the 7-Series-style boot lid works much better in the coupe form and isn’t unlike the "whale tail" of 911 Turbo.

Inside, the cabin of 6-Series has good style and good plastics, but not enough leather and craftsmanship. Compare with Maserati 4200GT (its number 1 rival) it appeals to be too mass producing. Space in the rear, however, matches the Maserati. People up to 5ft 9in won’t find their heads rubbing the roof.

The 6-Series range starts from 630Ci with the familiar 231hp 3.0 straight-6 to the 333hp 4.4-litre 645Ci. A 500hp M6 will top the range eventually, but at the moment we can only talk about 645Ci. The BMW V8 is as smooth, willing and torquey as usual. With Valvetronic throttle control, it drinks surprisingly little petrol for what it delivers - 0 to 60mph in 5.4 seconds. But it is too quiet in the coupe, perhaps BMW ought to remove some of the sound insulation to please those love exploiting the power of the V8. Compare with Maserati’s V8, it is too civilized, no matter in terms of sound, throttle response or explosiveness. Its flat torque curve encourages its driver to be lazy. That means it is a nice motorway cruiser but a less exciting driving machine.

Yes, the 6-Series intends to be a more civilized coupe. You can order a very smooth ZF 6-speed automatic gearbox in the 6-series, a thing Maserati drivers can never dream of. If you want conventional driver involvement, BMW still provides a slick 6-speed manual and a SMG sequential-shift version of the manual.

The standard suspensions setting provides a sounded balance between body control and ride quality, which isn’t a surprise considering BMW wants its mass production coupe to suit the taste of most buyers. Optional active anti-roll bar (taken from 7-Series) gives it terrific cornering stability without leading to more fun. Yes, the 6-Series understeers less than the 5-Series and it steers with more feel. It has remarkable grip and brakes in the tradition of German cars. But it doesn’t feel especially sporty or involving to drive. The engine noise and civilized power delivery is one reason preventing its driver from getting inspired, the lack of character is another reason. Like a late Toyota Supra Turbo versus Porsche 928GTS, it meets all the objective requirements but eventually fails to inspire its driver through steering, throttle, noise and chassis reaction. Therefore, in my mind, the original M635CSi is still the definitive BMW coupe.

M6

With M5 entered production last year, naturally the next development is M6. As 6-Series is derived from the 5-Series platform, M6 is also a development from the M5. The same 507 horsepower V10 powers both cars. What make difference is the packaging: the M6 is slightly wider, 9 cm lower and 45 kg lighter. Well, the last one is not very impressive indeed, considering the M6 lost 10 cm wheelbase, 2 rear doors and a proper rear seat.

BMW told us it tried very hard to reduce weight. Apart from the aluminum bonnet, aluminum doors, thermoplastic front fends and composite boot lid already found in the regular 6-Series, the M6 adopted very thin forged aluminum wheels - each saves 1.8 kg - and a carbon-fiber roof panel like M3 CSL. The latter saves just 4.5 kg, but its benefit to center of gravity should not be ignored. Anyway, 45 kg lighter than the M5 is not something you can applause, neither is the 1710 kg kerb weight.

One of the reasons is the V10 engine. It's a source of magic as well as a cause of overweight. At 240 kg, this engine is 3 times heavier than the other BMW V10 engine (well, that engine was only sold to Frank Williams). But by any standard 240 kg is not something in compliance with BMW's over-advertised "Lightweight Concept". The fact hurts: Porsche has a V10 that undercuts the M-Power by 26 kg yet produces 100 more horsepower.

This make the M6 a strange thing. Its engine, suspension tuning and tires work every bit like a sports car. But its size and weight says otherwise. When you switch the power mode to P500, flick the suspension damping and steering servo control to Sport mode and the gearbox to S6 mode, floor down the throttle and the V10 screams crazily (and addictively), pushing your neck hard on the headrest, storms to 60 mph in 4.5 seconds and 100 mph in something around 9.5 seconds. Oh my God, this is the supercar territory ! well, M5 was already in the supercar territory.

Steer the M6, it has the meaty feel and high accuracy like its saloon brother. Just everything goes faster and harder. Thanks to the wider track and lower center of gravity, it corners even faster than the M5. The soft-compound Pirelli P-Zero Corsa tires - the same one as Ferrari 360 Stradale and 911 GT3 RS - provide incredible grip. The M6 has a little understeer in default, but when you switch off DSC and apply power to the rear wheels, it can drift cornering as beautifully as M5.

But the advantage over M5 is too slim. At the same time you lost the proper 5-passenger accommodation and you pay £80,000 for the M6 compare to the M5's £65,000. Moreover, the M6 rides harder and harsher than the saloon - itself was already too hardcore to some people.

Ridiculously, M6 is supposed to be a high-performance GT rather than a sports car. But its suspensions - even with 3 modes of damping to choose from - is even harder than pure sports cars like 911 and Noble M12. This is partly blame to the stiff sidewall P-Zero Corsa tires, but mostly because BMW tried to hide its size and weight by firmer suspension setting. This means M6 is not a good companion for cross-country trip.

Fast though it is, the car has a couple of problems prevent it from matching real sports cars. The first one is lack of steering feel. The second is a brake prone to fade after continuous hard use. Ironically, both problems are succeeded from the M5 because they share the same steering rack and brakes. Unfortunately, we cannot forgive these in a car supposed to be sportier than M5.

So, what is M6 ? it is neither a sports car nor a grand tourer. It is not as sensible as M5, nor as charismatic as Porsche 911. More problematic is: it is really expensive. You can buy a dedicated sports car like 911 Carrera S or even GT3 for less money.

In fact, its predecessor M635CSi had the same pricing problem. Back in 1986, M635CSi was sold for £41,000, more than the contemporary Porsche 911 Carrera by £10,000. But M635CSi was not just about 286 fire-breathing horsepower. It was also a beautifully-styled, elegantly-built, good riding and comfortable 4-seater coupe. It provided many things that traditional sports cars and grand tourers lacked of. That's why M635CSi had become a classic, the definitive BMW performance coupe.

The latest M6 has almost doubled the power from M635CSi, but it falls into an identity crisis. Today the BMW top coupe is neither as fun to drive as Porsche 911, nor as competent (the poor brakes, the lack of feel), nor as comfortable to ride, nor as beautiful, and it still ask for more money. That's the problem.

Specifications

General remarks

	645Ci	M6
Layout	Front-engined, RWD	Front-engined, RWD
Chassis	Steel monocoque + aluminum front structure	Steel monocoque + aluminum front structure
Body	Steel, aluminum, plastic, composites	Steel, aluminum, plastic, composites
Length / width / height	4820 / 1855 / 1373 mm	4871 / 1855 / 1377 mm
Wheelbase	2780 mm	2781 mm
Engine	V8, 90-degree	V10, 90-degree
Capacity	4398 cc	4999 cc
Valve gears	DOHC 32 valves, DVVT, VVL (Valvetronic)	DOHC 40 valves, DVVT
Induction	-	-
Other engine features	-	-
Max power	333 hp	507 hp
Max torque	332 lbft	383 lbft
Transmission	6-speed automatic	7-speed automated manual
Suspension layout	F: strut R: multi-link	F: strut R: multi-link
Suspension features	Active anti-roll bar	Adaptive damping
Tyres front/rear	245/45WR18	F: 255/40ZR19 R: 285/35ZR19
Kerb weight	1620 kg	1710 kg
Top speed	155 mph (limited)	155 mph (limited)
0-60 mph (sec)	5.4* / 5.3**	4.5 (c) / 4.7* / 4.1**
0-100 mph (sec)	13.2* / 13.4**	9.7* / 8.9**
Performance tested by:	Autocar, *C&D

	630i	650i
Layout	Front-engined, RWD	Front-engined, RWD
Chassis	Steel monocoque + aluminum front structure	Steel monocoque + aluminum front structure
Body	Steel, aluminum, plastic, composites	Steel, aluminum, plastic, composites
Length / width / height	4820 / 1855 / 1374 mm	4820 / 1855 / 1374 mm
Wheelbase	2780 mm	2780 mm
Engine	Inline-6	V8, 90-degree
Capacity	2996 cc	4799 cc
Valve gears	DOHC 24 valves, DVVT	DOHC 32 valves, DVVT, VVL (Valvetronic)
Induction	-	VIM
Other engine features	DI	-
Max power	272 hp	367 hp
Max torque	236 lbft	361 lbft
Transmission	6-speed manual	6-speed manual
Suspension layout	F: strut R: multi-link	F: strut R: multi-link
Suspension features	-	Active anti-roll bar
Tyres front/rear	245/50WR17	245/45WR18
Kerb weight	1530 kg	1650 kg
Top speed	155 mph (limited)	155 mph (limited)
0-60 mph (sec)	5.9 (c)	4.9 (c) / 5.0*
0-100 mph (sec)	-	12.3*
Performance tested by:	*C&D