Classic Performance - Mercedes Benz 500 SL

This article was first published in 2000.

As the inventor of the horseless carriage, Benz started the transportation revolution. Over a century later, Mercedes Benz is one of the most desired and coveted marques; the company's pedigree is unquestionable.

The 500 SL's ancestry can be traced directly to the 190 and 300 SL's from the 1950s. These were the convertible versions of the legendary "Gull Wing" Mercedes. Stunning both in appearance and in performance, they were lusted after by schoolboys, businessmen and attention-seeking blondes alike. Nothing has changed...

The WDB129 series 500SL was released in 1990, replacing the WDB107 series which ran for the previous 18 years. The styling captured the essence of these predecessors, while gaining a modern, muscular stance. Ten years later it is still considered attractive. The body has received only ongoing minor upgrades - clear indicators, revised bumpers, side air vents and tail lights being the most obvious.

To describe the body in a word would be to say 'solid'. Everything opens and shuts with the precision and the 'clunk' expected from a German car. The penalty for such rigidity is its hefty weight - 1910kg. To put that into context, the car is only 120mm longer and 120mm wider than a Impreza WRX - and a whopping 640kg heavier. Body shake and scuttle are virtually non-existent and require a combination of high speed and extremely rough roads to occur. The body rigidity is noticeably better than the same year BMW 3 series convertible.

The 500 SL has an all alloy quad cam 5 litre V8 developing 235kW at 5600 rpm. Torque is an enormous 470Nm at 3900 rpm. The quad overhead cams directly operate the four valves per cylinder, with the inlet camshafts having variable timing. Twin cold air ducts feed air from beside each headlight to the twin air boxes mounted on top of the engine, which in turn ducts to a single throttle body. The alloy block is silicon impregnated, thus requiring no steel liners for the bores (a similar system was used in the Porsche 928). This makes it critical to not overheat the engine. The compression ratio is 10:1, with two knock sensors keeping any pinging in check.

Initially the transmission was a 4-speed overdrive automatic; 1992 saw it upgraded to the 5-speed adaptive shift automatic. In this transmission 4^th gear is 1:1 and 5^th gear an overdrive. The gearbox literally adapts to the driving style of the driver. It is silky smooth and quick up through the gears when driven sedately, but when driven aggressively it finds the right gear for every occasion. Full throttle from a steady 60 km/h and the gearbox choses the lowest possible gear (1^st!) to obtain maximum acceleration. Driven like this the car jumps to 80 km/h before changing to 2^nd gear. The gearbox also senses braking and changes in direction. For example, when braking into a corner, the gearbox will downchange a gear. The final drive ratio is 2.65:1, a ratio better suited to (Auto)bahnstorming than Australian roads, although the 470Nm of torque copes with the tall ratio surprising well. The car is electronically speed limited to 250 km/h.

The front suspension is a control arm style with adaptive damping. The rear suspension is an independent 5-arm multi-link setup, also with adaptive damping. The adaptive damping system is controlled by a body computer that measures road speed, lateral g-force, steering position and road surface condition. It then calculates the required damping rate, although there is also an in-cabin selection for normal or sport mode damping. 'Normal' mode can only be described as being on jelly - suitable only for people over 60 with bad backs. 'Sport' mode is more realistic, being firm but without jarring over potholes.

The ride height can be adjusted to 3 preset heights:

• 60mm above normal (bush bashing?)
• 35mm above normal (speed bumps )
• Normal (cruising )
• 15mm below normal (lowers itself automatically over 120 km/h)

All the 500SL's came standard with traction control. When wheelspin is detected, the engine output is (rather aggressively) cut.

In 1993 the 500SL was revised and renamed the SL500. Only subtle detail changes occurred on the outside, with the major changes occurring underneath. The traction control system was superseded by three control systems:

• ETS - Electronic Traction Support - works by applying brakes to the spinning wheel(s). This function works up to 40 km/h.

• ASR - Acceleration Skid Control - works over the entire speed range to improve directional stability by applying brakes to either rear wheel reaching its traction limit.

• ESP - Electronic Stability Program - uses road speed, lateral g force, steering yaw position inputs to increase stability when it detects understeer and/or oversteer. (For more on this system go to "Electronic Handling")

On the road, the 500SL is a big heavy car which wants to understeer, and a lot of body roll only exaggerates this handling trait. Not discounting the sheer grip provided by the 225/55 16 Pirelli's - or the unmovable rear end - the reality is you won't punt this car through corners as quickly as a WRX. In fairness however, if you are prepared to feed in the steering progressively and work with the understeer, you won't be too far behind. You will definitely be ahead of any IRS Commodore..... and all of this is done in absolute comfort!

In the event you manage to roll a 500SL, it has an automatic roll bar that pops up in milliseconds. For nervous drivers, a button on the centre consul can also raise the roll bar. The steering is recirculating ball, with 3 turns lock to lock giving an amazingly small turning circle. Mercedes are not renowned for a precise feel to their steering - and this car is no exception. However, the steering wheel is electrically adjustable for rake and reach, with the reach adjustment allowing you to place the wheel hard up against the dashboard, a la Porsche 911 style. Even if it does nothing to improve the steering, it certainly feels better to use! Mercedes pioneered ABS brakes in road cars back in 1983 and the brakes are as close to perfect as you will find anywhere. The driver's concern is more likely to be - can the car behind stop in time?

The interior is typical Mercedes - understated luxury that lacks for nothing while still looking austere. The bucket seats are monolithic in size. The seat belt anchors are part of the seat frame, thus the seat belt is always in the same place when you reach for it. The seats are electrically adjustable in any direction and have three memory positions. This function also adjusts the steering wheel and mirror positions at the same time. Annoyingly though, the centre rear vision mirror doesn't change in position. Idiosyncrasies include the fact that you cannot extract the ignition key until you take your foot off the brake pedal, and the handbrake design uses a foot pedal to activate and a hand lever to release. Identical to that of a LH/LX Torana, come to think of it....

The roof is fully automatic, operated by a button on the centre console and taking only 15 seconds to fully raise or lower. The car must be stationary for the roof motors to engage. At one stage the test vehicle's roof stopped half way through closing (and so did our hearts!) A quick call to a Mercedes service manager revealed that - due to ignorance - this is apparently a common problem! The computer must be allowed to follow its full logic process, that is: lower windows, lower roof, raise windows. If you stop this process before the windows finish the cycle, after a number of times the computer becomes confused, and ceases to drive the roof for fear of damaging it. The solution is to manually shut the roof, and lock it with the tool supplied (2 minutes work) - and then the computer is happy.

The test car has had several easy, cheap modifications made to it:

• There are plastic shields normally located in front of the cold air ducts, placed there to reduce induction noise levels to ADR requirements. These were simply unclipped and removed.

• The Mercedes centre and rear mufflers were replaced with a single 2.5-inch straight-through muffler.

A G-tech test showed 0-100 km/h in 6.0 seconds, and 14.1 sec at 168 km/h for the quarter mile. These were done on a 29 degree C day with one occupant and half a tank of fuel.

Owning a 500SL will start at A$90 000 for a 1990 model, increasing to A$240 000 for a 1998 model. Operating costs are minimal, considering the cost of the car. Intermediate services are around A$400, with major services around A$800. The mechanicals are regarded as bullet-proof if regularly serviced. The major expenditure to be budgeted for is the replacement of the suspension air cells at approximately 100 000 km. Cost is A$3000 -A$4000 (ouch!).

But with beauty, performance and retained value on its side, long-term ownership could be one on-going pleasurable experience....