It's seen more engine changes than a cross-country freight train, but the BMW 6-Series remains a thing of beauty and a driving joy. It originated in 1973 to succeed the aging Wilhelm Hofmeister-styled coupes that began with the four-cylinder 2000CS. Development work was initiated under chief engineer Bernhard Osswald and completed by his successor, Karlheinz Radermacher. What bowed at the Geneva Salon in March 1976 was essentially a rebodied version of the recently introduced 5-Series sedan, powered by the M-52 "big-block" six of the superseded 2800CS/3.0CS coupes.
Penned by the artistic Paul Bracq, BMW 6-Series styling was -- and is -- modern and handsome, with BMW's familiar "twin-kidney" grille, broad hood and deck areas, and tall, glassy greenhouse. Unlike its pillarless predecessors, the BMW 6-Series had B-posts, though they were quite thin and, finished in matte-black, hardly noticeable. Karmann continued to supply bodies, but final assembly now took place at BMW's Dingolfing factory, not the coachbuilder's Osnabrück works.
Chassis design followed the well-established formula laid down with the pivotal "New Class" sedans of 1962: all-coil suspension with front MacPherson struts and rear semi-trailing arms, plus recirculating-ball steering. As BMW's new flagship, the BMW 6-Series got disc brakes at the rear as well as the front.
It also introduced two innovations: variable-assist power steering, which decreases boost as engine speed increases for better road feel, and the comprehensive Check Control warning-light system that keeps tabs on engine systems, fluid levels, and exterior light bulbs. (Both would spread to other BMW models.) The 2 + 2 cabin featured a pair of deeply bucketed rear seats separated by an extension of the front center console, which in turn mated with a new angled-middle "Cockpit Design" dash (now another BMW hallmark).
The BMW 6-Series arrived in Europe with the existing 3.0-liter carbureted six as the 630CS. Initial transmission choices comprised 4-speed Getrag manual or 3-speed ZF automatic. The U.S. version appeared for model year 1977 as the 630CSi, the "i" denoting Bosch L-Jetronic fuel injection, necessary to maintain some semblance of performance in the face of stiffening federal emissions standards.
Though critics loved the BMW 6-Series' handling, comfort, and refinement, they judged outright performance disappointing. But BMW was ready with a more powerful, 3.2-liter engine, substituted on both sides of the Atlantic for 1978. Curiously, these cars were badged 633CSi, not the more logical "632CSi."
Since then, the BMW 6-Series has evolved through increasingly potent powerplants with chassis upgrades to match. The first came with the European 635CSi of 1978, identified by special front and rear spoilers, discreet bodyside striping, and wider, lacy-spoke Mahle-BBS alloy wheels, plus a 3.5-liter 218-bhp M-90 engine and close-ratio 5-speed manual gearbox.
Alas, a 635 didn't reach North America until 1985 and was much tamer, though it boasted three important chassis changes: "double-pivot" front control arms and 'Track Link" rear suspension (borrowed for 1983 6s from the big 7-Series sedans to reduce oversteer tendencies in hard cornering) and Bosch anti-lock braking system (ABS). By this time, all 6s had standard 5-speed manual and optional 4-speed automatic transmissions, the latter with electronic shift control.
More exciting was the limited-production M635CSi, presented at Frankfurt in September 1983. Developed by BMW's Motorsport arm (hence the "M"), it packed a modified version of the twincam, 24-valve M-88 powerplant from the mid-engine Ml (see entry). Performance was vivid to say the least: just 6.4 seconds 0-100 km/h (62 mph) and a blistering 158 mph maximum.
For 1987, BMW finally brought this autobahn stormer to North America as the M6, losing little performance in the process. Though luxuriously furnished -- twin air conditioners, eight-way power front sports seats, eight-speaker sound system, hand-stitched leather on seats, dash, and door panels -- it's blitz schnell off the line and cruises easily at 140 mph. Desirable?
In exchange for less performance, less money bought you the equally posh U.S.-market 1987 L6, available only with automatic. Standard manual transmission returned for the renamed '88-model 635CSi, which offered more power via the higher-compression engine from the big second-generation 735i sedan. Closer-fitting bumpers were among several updates throughout.
Alas, nothing lasts forever, and BMW's new 5-Series sedan (scheduled for early-'88 release at this writing) inevitably means that this beautiful bolide will be replaced (reportedly by a smooth all-new high-tech design). The good news is that the 6-Series we've come to know and love should continue through 1990 at least. It'll be one tough act to follow.
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