300 The four-door 300 (W186) was introduced at the Frankfurt Motor Show in April 1951 and entered series production in November 1951. It had no "a" designation, which was informally added, along with the "b" and "c", by later enthusiasts seeking to distinguish the three W186 generations. Available as both a saloon and cabriolet, it featured graceful modernist bodywork atop Mercedes' proven X-frame chassis. An all new 3.0 L (2996 cc/182 in³) overhead cam, aluminum head
M186 straight-6 was coupled to a 4-speed all-synchromesh manual gearbox. Twin downdraft
Solex carburetors and an innovative diagonal head-to-block joint that allowed for oversized intake and exhaust valves produced at a 6.4:1 compression ratio. in
Bonn Designed to give reliable service under prolonged hard use, the engine featured deep water jackets, thermostatically controlled oil cooling,
copper-lead bearings and a hardened crankshaft. With no natural cruising speed, the car could sustain anything up to its maximum speed all day, road conditions permitting. The combination of a rigid X-shaped ovoid steel tube frame and four-wheel
independent suspension provided surprisingly nimble handling.
Double wishbones,
coil springs, and a
stabilizer bar were used up front and Mercedes' typical double coil spring
swing axle in rear. An innovative dashboard-operated rear load-leveling suspension engaged a
torsion bar to increase stiffness by one-third when needed, and a pedal-operated central lubrication system kept friction points silent. Brakes were hydraulic drum all around, steering worm-and-sector, replaced in 1952 by
recirculating ball. A total of 6,214 saloons and 591
Cabriolet Ds, retroactively referred to as the "300a" series, were produced through September, 1955, including a brief 300b run incorporating elements of the 300c's partial facelift prior to its debut.
300b The
300b (W186) was introduced in March 1954, adding vacuum assisted power brakes and front door vent windows. Engine power was upped to via different Solex carburetors and an increased compression ratio of 7.5:1.
300c The
300c (W186) made its debut in September, 1955, adding a larger rear window and optional 3-speed
Borg-Warner automatic transmission. It was priced at $10,864 in the United States (DM 22,000 on the home market), with the convertible almost a third more at $14,231 (DM 24,700). A special
Innenlenker limousine (also called the
Type 300 Lang) with on a 20 cm (7.9 in) longer
wheelbase became available from July, 1956, priced at DM 25,000. A total of 1,432 300c saloons were produced through July, 1957. Only 51 300c series Cabriolet D's were built through June 1956, when the model was dropped. == Successor ==