For many, the M5's subtle appearance is just fine, allowing the occasional exploration of the 500-bhp V10 motor's talents without attracting unwanted attention. But for those who think BMW's fastest saloon is too stealthy, they could always send theirs to Hamann Motorsport for the equivalent of a big dose of steroids. Hamann calls this conversion its Edition Race.
Although our test car, kindly loaned by one of Hamann's regular customers, is carbon black and therefore relatively low key, its wheelarch extensions, spoilers, big wheels and unmistakeably aggressive stance certainly add presence. The Edition Race front bumper/spoiler is a direct replacement for the factory item, but features a larger central air intake with mesh grille, brake cooling ducts and a pair of round driving lights wired to the high beam switch. The sides of the bumper are also drawn out to meet the contoured box arches that sweep aft in a half teardrop shape.
The new side skirts do more than just visually connect the front and rear arches. Wind tunnel testing has proven that they also lessen turbulence around the tires, improving the drag coefficient. The rear arch extensions are two-piece, one on the rear door and one on the rear wings. They merge into the new rear bumper with its big cut-out for the four exhaust tips and small diffuser aerofoil below. The rear window rooftop spoiler helps to clean up separating air before it spills down to the one-piece trunklid spoiler.
Filling out the bigger wheelarches requires some serious rolling stock. Hamann recommends its own-design 21-inch wheels: nine inches wide up front, 10.5 at the rear with 255/30-21 and 295/25-21 tires respectively.
Apart from its fabulous handling, the BMW M5 has a great secondary ride-thanks to well-chosen springs and a perfectly calibrated active damping system. Not wanting to upset such a fine ride/handling balance, Hamann has opted for a carefully-rated lowering spring set that drops the ride height 1.2 inches in front and one inch at the rear.
M cars' brakes are fine for road use, but track day junkies have often found them wanting. Hamann's big brake kit uses 15-inch vented discs in front, clamped by massive eight-pot alloy calipers. The stock rear brakes use uprated pads.
Although wide wheels and tires look good and boost handling and grip, they eat into acceleration and top speed because of their extra drag. A modest power boost of 20 bhp may be consumed just maintaining the car's original performance. Hamann offers three stages of engine tuning for the M5. The first of these simply deletes the 155 mph top speed limiter, so an otherwise standard car in peak condition can reach 200 mph. But Hamann's 20- or 21-inch wheel-and-tire combinations limit that to 186 mph, illustrating the negative impact that drag from larger footwear has on straight-line performance.
Stage two is a comprehensive ECU remap, which optimizes the fuel and ignition curves and is good for an additional 30 bhp and 11 lb-ft of torque. However, this only applies in countries where good quality fuel of at least 98 octane is available. Stage three boosts power by a much more significant 60 bhp, but more important is the 40 lb-ft increase in torque. The bigger numbers are achieved by opening up the breathing with a sport air filter, while exhaust backpressure is reduced by equal-length exhaust headers, sport catalytic converters and three-inch diameter free-flow exhaust pipes with four outlets. The ECU remap optimizes fuel and ignition curves for the new parameters.