Mercedes-Benz SLK55 AMG R171 vs. BMW Z4M Coupe E86 and Porsche Cayman S 987C group test 2017 / 2018

Three-hundred thundering horses. Who says you need deep pockets for massive performance? Paul Hardiman samples sub-£20k sports coupés from BMW, Mercedes and Porsche. Photography Tony Baker.

A trio of German modern classic powerhouses for a pittance 300BHP SUPERCOUPÉS – FROM £15k. A posse of powerwagens BMW Z4M E86 takes on Mercedes-Benz SLK55 AMG R171 and Porsche Cayman S 987.

Mercedes-Benz SLK55 AMG R171 vs. BMW Z4M Coupe E86 and Porsche Cayman S 987C group test

The badging on the three rivals is as disparate as their individual characters, but all three promise huge pace via an abundance of torque and horsepower.

Do we all agree that at 200bhp cars by and large become interesting, that by 300bhp things are beginning to concentrate the mind, and that once you have 400bhp propelling a long ton everything starts to feel really quite rapid? Good. Now we’re sitting comfortably.

Well, two of the cars you see here – Mercedes-Benz SLK55 AMG R171 and BMW Z4M Coupe E86 – are slap in the middle of that 300-400bhp range and the Porsche Cayman S 987 isn’t far behind, with a similar power-to-weight ratio. All three can currently be had for under £20,000 (less than half their price new), which considering the performance on offer looks a bargain. Add rock-solid build quality, plus practicality sufficient to mean that they can be daily drivers, and we’re on to something worth investigating.

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Frontal styling of the second-generation SLK was heavily influenced by contemporary F1 designs. Top: broad hips allow roof to fold away into the tail.

Mercedes has been doing roadsters built and imbued with the same sense of solidity as its saloons since 1955, with an evolution of styles though the various SLs, Pagoda and Panzerwagen, before arriving at the C-class-derived R170 SLK of 1997. That was replaced in 2004 by the R171 with its 30mm longer wheelbase and ‘F1-inspired’ nose designed by Steve Mattin. It was facelifted in 2007, and powered by everything from a 1.8-litre 160bhp supercharged ‘four’ through to a 3.2 V6 and 5.3 V8, the most powerful version hand-built by AMG. All had a folding hardtop marketed as the Vario-Roof.

Like the R107 and R129 before it, you get the feeling that the SLK doesn’t want you to know too much about what’s going on under the skin; it just gets on with it. The steering is light and a little dead but the grip from the 225- and 245-section Contis is massive, and the V8, buried under all-cloaking beauty covers, is astonishingly free-revving for a big-capacity motor. Prod is, er, prodigious but despite being the weightiest car here it’s not the heaviest carbon-emitter: that honour goes to the BMW. Surprisingly, the Mercedes is not the biggest here, being only 8mm less stubby than the Z4, while the Cayman is almost a foot longer.

Aside from that marvellous motor, where you find endless amusement in the SLK is in its appointments. As well as the retracting roof – as long as the boot isn’t too full – there are heated seats and a pair of ‘air scarfs’: warm-air blowers in the head rests, aimed at the back of your neck to ensure you stay nice and toasty with the top down.

Mercedes-Benz SLK55 AMG R171

Stylised cockpit of the Mercedes has buttons galore; AMG-built 5439cc V8 boasts monumental 375lb ft of torque for easy pace; elegant turbine rims.

Then there’s the gearbox, a seven-speed auto offering endless permutations of confusion. There’s the stick, for Park, Reverse, Neutral and Drive, as usual. Once the lever’s in D, slapping it right or left gives you up or downchanges, and you can achieve the same with buttons on the back of the wheel. A further switch in front of the gate gives three modes: Sport, Comfort or Manual, with a digital readout between the main gauges to let you know where in all of this you are. This is very definitely a driver aid because the SLK doesn’t seem to care which ratio it’s in. It swaps cogs smoothly in all modes, holding the gears much longer in Sport, but doesn’t blip on downshifts like a Ferrari. Column-mounted paddles that apparently came attached to faster software were an option.

There’s so much torque from the motor – as owner John Cummings says, “it likes hills” – that once you’ve got bored with playing tunes on the transmission it’s just as quick to leave it in auto and watch the world spool by, as rapid as you like, in perfect smoothness. It may not talk to you much, the Merc, but you feel you can trust it to make the decisions while you enjoy the scenery.

[trailer_box style=”15″ image=”images/mews2015/drive2015/Porsche-Cayman.jpg” background=”#a788aa” title=”Porsche Cayman S 987C” url=”” target=”blank”][counter count_end=”171″ prefix=” Top Speed ” suffix=” MPH” count_color=”#ffffff” text_color=”#ffffff”]Porsche Cayman S 987C[/counter][/trailer_box]


Cayman’s slippery styling is closely related to that of the Boxster, with which it shares its platform, but the extra rigidity improves the driving experience.

The Cayman was criticised at launch in 2005 for being a second-generation, Typ 987 Boxster with a roof instead of an expensive retractable top, yet costing £4000 more. It’s a more subtle device than that, though. The extra rigidity conferred by that handsome teardrop lid stiffens the chassis and makes for a very together car.

There are some similarities to the 911, of course – the motor is the same as a 997’s, and the steering feels similar to a 997 or 964; not as talkative as an early 911 but better than the deadened all-wheel-drive 996. No surprise because the 987 platform shares a lot with the 997, itself a heavily updated 996, but with the engine in front of the gearbox rather than behind it. The change of the six-speed Getrag is about on a par with a G50 3.2 Carrera, even though it has more linkage. It’s slick for a Porsche, and the ratios are flatteringly closely stacked.

What is the same as a 911 is the linear power delivery from the water-cooled M97 powerplant. The turbine-like smoothness common to all flat-six Porsches appears devoid of dips or spikes, making it feel less powerful than it is, although with only 251lb ft – the same as a modern 2-litre turbodiesel – it’s noticeably less torquey than its rivals. It’s happy revving to 7000, with the sweet spot past 5200, although it’s a little softer, less urgent, once beyond the power peak at 6250. In 911 style, it feels unburstable and able to sustain those revs for longer than you can.

Porsche Cayman S 987C

Workmanlike cockpit of the Porsche; flap in midengined Cayman’s luggage area gives access to fluid reservoirs; smaller 17in alloys fitted to this car.

Where it’s unlike a 911 is in its singular stability. There’s none of the shoulder-writhing that you feel from behind you in the rear-engined car, and it appears less sensitive to throttle changes mid corner – although some of that might be down to Porsche’s very benign stability control (benign as in, you don’t notice it). Owner Jeremy Laird says that in trackday situations it responds well to a little brake trail on turn-in to bite the front and unsettle the rear, and that it gives much more feedback on 17in wheels with 205-section front boots than on the standard 18s. He fitted 17s in order to run winter tyres and preferred the feel so kept them on, with taller rubber than standard.

The slightly plasticky feel to the cabin comes as a surprise, although that’s mostly down to the cheap-looking leather wrapping the wheel. The rest of it is much better quality, and well screwed together (most of them by Valmet in Finland). In terms of practicality, as well as storage under the hatchback there’s a decent front boot. Getting at the motor for any more than topping up oil and water (via a flap in the rear compartment) involves half an hour with some tools, though.

[trailer_box style=”15″ image=”images/mews2015/drive2015/BMW-Z4M.jpg” background=”#a788aa” title=”BMW Z4M Coupe E86″ url=”” target=”blank”][counter count_end=”155″ prefix=” Top Speed ” suffix=” MPH” count_color=”#ffffff” text_color=”#ffffff”]BMW Z4M Coupe E86[/counter][/trailer_box]


The sharp-suited BMW has the most controversial styling of our trio, but is instantly recognisable and has tremendous visual presence out on the road.

The Z4M coupé filled a gap left when the much-missed BMW Z3M was retired in 2002. Jackknife yourself in (it’s the lowest of our trio) and even with its slight HR Giger overtones there’s no doubt that you’re in a BMW even before you start it, thanks to the clearest instruments. Dark plastics – complemented on this one by a rare gloss-black ‘piano dash’ – contrast with light leather that doesn’t look as if it will wear very well. But all that is irrelevant when you fire it up.

The B32 version of the legendary iron-block S54 has that deep-chested boom beloved of BMW E9 CSL lovers. Unlike the old single-cam M30, though, it manages to combine this with astonishing revvability, pulling hard and strong right round to the 8000rpm redline with a sonorous yowl. Apparently, BMW has had to electronically replicate this for the latest M3.

The Z4M is not the lightest here but feels it. It is the quickest – both subjectively and on paper – and, like the devil sitting on your shoulder, its slightly deviant tendencies are always inviting you to play. The proximity of your behind to the rear axle – it’s Caterham-like in that respect – adds confidence, as does the chunky though communicative hydraulically assisted steering.

BMW Z4M Coupe E86

Light-coloured hide and piano black fascia give BMW cabin a lift; 338bhp straight-six has double-VANOS variable timing; aftermarket 19in wheels.

With its short wheelbase it is very tail happy but it does look after you when it decides to step out, rather like an M3. We didn’t try turning off the Dynamic Stability Control on greasy January roads, but if you want the full one-armed paper-hanger effect, just press the Sport button. Throttle response sharpens noticeably, so when pushing on the driver always has something to do and can’t quite relax.

Even with the clever variable-clinch M-diff helping as much as it can by optimising traction, this is one you need to be in front of, although you’ll always have brakes, even when it’s wet. When it senses rain the Z4M periodically kisses the discs with the pads to dry them, so there’s no lag if you hit the pedal. Only the gearchange disappoints slightly if you are used to ’02 slickness; the six-speeder is precise, but notchy.

So, which one? Depends what you want. They are all faster than you need and, thanks to competition raising the game, there’s not a duffer. All can be had for roughly the same: £20k for a decent one, or £5k less if you take a gamble. All return 25mpg in real life, and much less if you boot them. At £500 a year (£295 for any registered before March ’06), the Porsche is the least painful to tax; the others are in the full-cholesterol top-guzzler band and sting you for £515. The SLK will go full stonk and ripple tarmac or simply meander, and looks after itself, whatever you do with the gears. The slightly nervy BMW wants to play all the time, although its constant demands could get wearing. The Porsche just packs in the miles as the super-sharp and rock-steady device that it is.

There’s no ‘best’ until you decide which way your focus drops, although on paper the Merc has it for its performance and versatility. The BMW is basically a hooligan, and with its Mantaray envelope packing plenty of muscle looks as if it’s drifting even when it’s standing still. The no-frills and slippery Porsche is for getting places fast and fairly discreetly, as the owner’s several Alpine trips attest. And the deliberately detailed Mercedes is for being seen in, with the added option of dropping the roof without compromising comfort, but just doesn’t involve you as deeply. Ultimately, it’s all about how naughty and brave, focused or laid-back you feel.

Thanks to the Red Lion at Chelwood Gate:



This is Cummings’ fourth SLK in eight years: “As a civil servant I couldn’t afford a car like this, but 20 years ago I took out a lot of insurance policies for when I retired. I got a 2litre first, then another, and then traded that for a V6, but I’d wanted a V8 since hiring an R107 a few years ago. This was £3000 more than my V6, though it was older.” He joined the MB Club and shows the car (in matching suit, shoes and tie): “I just love it – the best bit is the handbuilt engine, but I always drive it within its limits.”


Sold/number built 2005-’2011/9541

Construction steel monocoque

Engine all-alloy 5439cc V8, Bosch ME 2.8 injection

Max power 355bhp @ 5750rpm

Max torque 375lb ft @ 4000rpm

Transmission seven-speed auto, RWD

Suspension coil-spring struts front with two lower links, multi-link rear

Wheels and tyres 225/40 and 245/35×18

Length 13ft 5 ½ in (4099mm)

Width 5ft 10 ½ in (1794mm)

Height 4ft 2 ¾ in (1287mm)

Weight 3473lb (1575kg)

0-60mph 4.9 secs

Top speed 155mph (limited)

Mpg 23.5

Price new £51,975


Laird has put 40k miles on his car in two years, most of that on a new engine under warranty – intermediate shaft (IMS) bearing and cylinder liner failures are well documented, although they affect few cars: “A Cayman is a 997 with the engine turned around – the front two-thirds are basically shared. It’s the modern-classic conundrum du jour, more a sartorial choice than a question of substance. Ultimately, the Cayman is a more compact and resolved driving tool than a 911 – and £10k cheaper.” 


Sold/number built 2006-’2009/n/a

Construction steel monocoque

Engine all-alloy 3387cc 24v four-cam flat-six, Bosch ME injection

Max power 291bhp @ 6250rpm

Max torque 251lb ft @ 4400-6000rpm

Transmission six-speed manual, RWD

Suspension coil-spring struts and wishbones all round, anti-roll bars f/r

Wheels and tyres 235/40 and 265/40×18

Length 14ft 3in (4340mm)

Width 5ft 10 ¾ in (1800mm)

Height 4ft 3 ½ in (1305mm)

Weight 2955lb (1340kg)

0-62mph 5.4 secs

Top speed 171mph

Mpg 27

Price new £44,250


THE OWNER Adrian Kitchin BMW Z4M E86

Commercial pilot Kitchin’s car came as a result of an insurance payout: “I lost my medical certificate and the policy covered loss of earnings, so my wife suggested that I buy something nice to cheer myself up. The Z4M seemed the most fun. The rules changed and I got my licence back, so am flying again. My wife thinks that I should sell the BMW, but she can see how much I love it. It’s been my daily car but is coming off the road soon for minor cosmetics, and then it’ll be a second car for fun.”


Sold 2006-’2008/4275

Construction steel monocoque

Engine iron-block, alloy-head 3246cc 24v dohc ‘six’, BMW/Siemens MSS 54 management system

Max power 338bhp @ 7900rpm

Max torque 269lb ft @ 4900rpm

Transmission six-speed manual, RWD

Suspension coil-spring struts front, multilink Z-axle rear

Wheels and tyres 225/45 and 255/40×18

Length 13ft 5in (4091mm)

Width 5ft 10in (1781mm)

Height 4ft 2in (1268mm)

Weight 3241lb (1470kg)

0-60mph 4.8 secs

Top speed 155mph

Mpg 23

Price new £42,245


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