Feature Flashback: 1991 BMW M5
Motor Trend totally missed out on the original 1988 model E28 M5, the hand-built version powered by a derivation of the 3.5-litre I-6 engine from the M1 supercar that BMWclaimed was the world’s fastest four-door at the time. Like early Model Ts, they were all painted black and only 1,239 of them were built to U.S. specs (prompting a class-action lawsuit because BMW had promised to send us no more than 500). So our first M5 test car was a 1991 model E34-generation example. Then, as now, the car shared its basic engine and chassis architecture with those of the top non-M 5 Series variant, which in those days was the 535i. This second-generation car was still hand built at BMW M GmbH in Garching, outside Munich, so the price premium was steeper—roughly 40 percent, as compared with today’s 25 percent bump. With that, let’s step back in time and take a spin in the brand-new E34 M5.
Both author Jeff Karr and Second Opinion provider Michael Brockman went on and on about the price: $58,450 to start, $58,700 as tested with heated seats (that’s equivalent to $106,000 today). “Why would somebody expend such a substantial pile of cash when the perfectly wonderful 535i is available for about $42 grand?” Brockman was less tactful: “What are you, nuts? $58,000 for a 5 Series BMW? You must be crazy. I just bought a house in Florida for a couple bucks more.” Karr’s opinion eventually came around to “Why not?”
BMW M Power
The engine was technically a mildly stroked derivation of the M1’s M88 twin-cam I-6, but that engine was originally based on the M30 block that still powered the 1991 535i in single-cam guise, so the engines are clearly related, if less so than today’s M550i and M5 mills. Thanks to improved fuel injection, a two-stage resonance supercharging intake manifold, and an increase in the redline versus the E28 M5 (from 6,800 to 7,200 rpm), the output increased from 252 hp/243 lb-ft in the E28 to 310 hp/265 lb-ft. Relative to the 535i’s 208 hp, that power bump was greater than the price premium—49 percent, so, a bargain!
Automatics of the 1990s were far less efficient than today’s, so no self-respecting sport sedan would be conceived without a stick. This one featured five ratios and a clutch with a “heavy diaphragm-type spring [that] is awkward to control.” Between the comparatively small 235/45ZR17 Michelin MXX2 tires and similarly short transmission and axle gearing, that torque issuing from that M engine had plenty of mechanical advantage on its way to the road surface. Of course, gearing like that doesn’t do the fuel economy any favors—EPA city/highway ratings were 11/20 mpg.
To house and cool the jumbo 12.4-inch front/11.8-inch rear M Performance brake discs, special 8.0-inch-by-17.0-inch forged aluminum wheels were designed with five blacked out spokes that got covered up by directional wheel covers designed to scoop air in toward the brakes for cooling. The dark gap between the rim and that inner cover made these wheels look for all the world like little steelies wearing covers shod in high-profile whitewall tires. Perhaps this contributed to its Q-ship sleeper status?
“Chassis balance is set for mild understeer, and the chatty front tires provide an audible warning when you’re about to enter the Twilight Zone.” Try as he might to provoke misbehavior, the M5 demonstrated mild understeer and no propensity to lapse into trailing-throttle oversteer. Clearly this one was not optimized for drifting the way its F90 successor is. He had praise for the surprisingly compliant ride on what passed for low-profile tires in those days, but he noted that they introduced a lot of road noise to the cabin.
6.4 Seconds to 60 mph!
…And 14.9 seconds to the quarter mile at 98.3 mph. “These are the numbers of an out-and-out sports car, and they belie the fact that the M5 offers the interior space of a good cross-country sedan.” (They’re also the numbers of a current Acura MDX.) Braking took 126 feet from 60 mph and lateral grip peaked at 0.85g—that’s 2 feet shorter and 0.01g grippier than today’s MDX. Of course, half the fun of today’s M5 is the sound. But back in the day, that wasn’t the case. “Not much exhaust noise makes it past the big catalytic converter and muffler system borrowed from the 12-cylinder 750iL, but the silky mechanical whir and turbine-like fan noise from underhood are seductive enough to boil blood.”
Few changes were made to the already opulent 535i interior, except to remove the center seat belt and install a large storage console and armrest in its place. Exterior changes were equally subtle, limited to the lowering effect of the tires and suspension and M5 badging front and rear. Karr’s parting words for the M5 were adoring: “It embodies a relentless pursuit of perfection and reflects a tangible love of high-performance driving for its own sake that you find in few automobiles and only one sedan. This one.”