2005 Cadillac STS: The Unexpected Challenger That Rattled BMW's 545i Dominance

In the mid-2000s, Cadillac made a significant stride in reclaiming its place in the premium luxury sedan segment with the introduction of the 2005 STS. After two decades focused on front-wheel-drive platforms, Cadillac finally presented a rear-wheel-drive V-8 sedan designed to directly challenge established benchmarks like the BMW 5 Series. This comparison, originally highlighted in an August 2004 MotorTrend article, positioned the Cadillac STS against the BMW 545i, proving to be an extremely close battle.

The 2005 Cadillac STS emerged as the successor to the long-running Seville, built upon the versatile Sigma platform, which also underpinned the edgy CTS sedan and the SRX crossover wagon. It showcased Cadillac's distinctive Art & Science design language, presenting its most pleasing and well-proportioned iteration to date. While a 255-horsepower 3.6-liter DOHC V-6 engine was available, the test model featured the robust 320-horsepower 4.6-liter Northstar V-8. For buyers in colder climates or those eyeing Audi, an all-wheel-drive system, borrowed from the SRX, was also offered.

Compared to the smaller, more sculpted CTS, the new STS boasted increased dimensions, being approximately six inches longer and wider, and an inch taller. This translated to enhanced rear-seat head- and legroom, greater front and rear shoulder room, and more generous trunk space. The preproduction STS V-8 test car had a base price of $47,495. With a substantial list of options, including adaptive cruise control, head-up display, Xenon automatic headlamps, 18-inch polished wheels with performance tires, performance brakes, performance cooling, Magnetic Ride shocks, ZF performance steering, a Bose surround-sound audio system with a six-disc DVD player, XM Satellite Radio, and Bluetooth communications, a limited-slip differential, decklid spoiler, premium wood trim, memory presets, four-way lumbar support, heated front and rear seats, a heated steering wheel, ventilated front seats, and extra-soft Tuscany leather seats, the estimated as-equipped price reached $63,455.

On the opposing side, the BMW 5 Series was completely redesigned for 2004. Although slightly longer, wider, and taller than its predecessor, the new 5 Series achieved weight savings through extensive use of aluminum in components such as suspension arms, subframes, the steering rack, brake calipers and rotor hats, the hood, front fenders, and a significant portion of the front structure forward of the windshield pillars. Powering the 545i was a potent 4.4-liter Valvetronic V-8 engine paired with a ZF six-speed automatic transmission, both sourced from the flagship 7 Series. This particular 545i carried a base price of $55,695. Its option list included a premium sound system with a six-disc in-dash CD changer, a rear sunshade, fold-down rear seats, park distance control, and a sport package (comprising performance tires, sport seats, lowered suspension, active steering, and active roll stabilization), along with satellite-radio preparation, bringing its total to $62,620. Notably, had the BMW been equipped with the optional navigation, adaptive cruise control, head-up display, and satellite radio found on the Cadillac test car, its price would have climbed to $68,215.

Despite both vehicles landing in the same $63,000 price bracket, offering sporty four-door designs, numerous luxury features, and V-8 engines with over 300 horsepower, they exhibited distinctly different personalities. The BMW 545i, with its new 2004 design, drew immediate attention for its controversial styling, an evolution of the architecture introduced on the 7 Series. Editors noted its taller profile, raised roof, and a 'bustle-like trunk' as a significant departure from previous, highly successful 5 Series designs. Some described its appearance as 'almost Japonic,' 'thick and chunky' in profile, and criticized the 'Kia Rio-like taillamps' as being out of place on a $60,000 car.

Inside, the new 5 Series effectively utilized its increased cabin length and height, offering ample rear-seat room. The driving environment was generally praised for being 'functional' with 'first-rate' controls that provided a 'precision feel.' However, the iDrive infotainment system, even in its revised form, remained a point of contention. While its intent to declutter the cabin by reducing physical buttons was appreciated, its execution required an excessive number of keystrokes for simple tasks, diverting the driver's attention from the road. One critic lamented the inclusion of 'less technogarbage people never asked for in the first place.'

When it came to driving dynamics, enthusiasts lauded the BMW 545i's capable and well-balanced chassis. The weight-saving aluminum front structure contributed to a near-perfect 50/50 front/rear weight distribution. Equipped with standard run-flat tires, the car delivered a firm, somewhat jouncy ride on imperfect roads. The tested car's optional sport package further enhanced its performance with stiffer springs and shocks, a lowered ride height, anti-squat and anti-dive geometry, and active roll stabilization, which virtually eliminated body roll in most driving scenarios. This made the car feel remarkably planted and capable of covering ground swiftly.

One feature that sparked controversy was BMW's active steering, with its variable-ratio technology capable of dramatically altering steering response from a slow 20:1 to a quick 10:1. While some appreciated the added speed at the corners of steering lock, others expressed concern over the loss of linearity, leading to uncertainty in high-speed corners or even clipping abutments in parking garages. An editor described it as varying with a 'strange algorithm,' making it difficult to predict the required steering input, especially when braking into tight corners where it would suddenly 'cut hard.'

The BMW's 4.4-liter Valvetronic V-8 engine, however, was universally praised. It eliminated the traditional throttle plate, electronically controlling airflow by varying valve lift. Combined with stepless variable valve timing for both intake and exhaust camshafts and a fully variable intake manifold, it produced a broad and robust torque curve. Output was a significant 35 horsepower increase over the previous 4.4-liter engine, making the 325-horsepower V-8 feel even more powerful. This was partly due to the ZF six-speed automatic transmission, whose particularly short first gear provided excellent torque multiplication for strong launches. While the transmission offered a seemingly endless supply of gear ratios for any situation, some found it prone to 'lunging' between gears during brisk acceleration. Additionally, under semi-hard braking, the transmission aggressively forced downshifts, unnaturally slowing the car even after the driver released the brake pedal in stop-and-go traffic.