The new model 250 broke fresh ground for Mercedes in having a new independent rear suspension using semi-trailing links instead of their famous low-pivot swing-axle. The six-cylinder engine was derived from that of the previous 250SE, and had the same over-square dimensions, but cylinder-centres were revised and the bores siamesed.
In place of fuel injecction were two Zenith twin-choke carburetors with progressive opening of the second chokes on full throttle as revs increased. It developed 130 bhp (net) at 5300 rpm, compared with the 150 bhp at 5500 rpm of the fuel injection 250SE, by then no longer in production.
Although just over 2cwt lighter, the 250 could not quite match the performance of its more powerful predecessor. The new car was better in many other respects and was, more importantly, cheaper. Acceleration was good to 80 mph, which could be reached in 26 seconds from rest allowing the transmission to change gear automatically at 17, 30 and 65 mph.
By using the selector to hold each ratio until the recommmended maximum shown on the speedometer (22, 47 and 73 mph) it was possible to save a further 1.2 seconds off that time, down to 24.8 sec. The 250 went on to reach 90 mph reasonably quickly (36.5 sec from rest), but acceleration then diminished rather markedly.
In real-world driving you would find the speedometer gradually creep up to an indicated 110 mph (true speed 104 mph) at which the car was happy to cruise indefinitely. When worked hard in the lower speed ranges the engine became disappointingly obtrusive, but noise levels did not increase in proportion to speed and above 70 mph it became relatively quiet.
One of the revelations, particularly given the 250 was not fuel injected, was how responsive the car was when cold. The. accelerator had to be pressed slowly down to set the automatic choke, and then the engine fired at once. A four-speed gearbox with floor or column change was the standard transmission, but the 250 could be optioned with the Daimler-Benz four-speed automatic.
The New Daimler Benz 4-Speed Automatic
The latter transmission used first gear for part-throttle starts from rest, that were previously obtained only with full throttle. The revisions to the automatic transmission made the gear changes appreeciably smoother than before, though there was still a sudden surge during full throttle upshifts. The selector was mounted on the floor, and worked in a stepped gate with neat nylon edges. It had a very smooth action, particularly appreciated when flicking the lever back for a quick downnshift to avoid the kickdown surge.
When a floor-mounted selector was fitted to previous models, the gate positioned neutral, reverse and park at the rear, towards the driver in that order. The 250 adopted the stanndard layout with the lower gear holds nearer the driver. As before, position 4 gave fully autoomatic driving; 3 eliminated top gear, but still allowed changes down to second or first; and position 2 controled only first and second gears. There was no positive hold for first gear, but the change-up point was 5 mph higher with 2 selected than in ordinary fully automatic driving with the lever at 4.
It was not always appreciated that the selector also affected the speeds at which the transmisssion would change down. For example, if the lever was moved from 4 to 3 there was an instant change down to third, but also the transmission was more ready to go down to second of its own accord than if left at 4. In position 4, the maximum speed at which full throttle kickdown would bring a change to second gear was 23 mph, but with 3 selected a kickdown change to second was possible right up to 30 mph.
Whichever way the transmission was used, the positive drive and willingness to change down in response to throttle made the car seem less fussy and more eager than with other types where a torque convertor is working busily all the time. There was fairly strong creep at the high tickover speed which was normal for this engine, but it was easy to slip the lever into neutral for any prolonged traffic halt. Selector positions were illuminated at night but in any case the positions were soon familiar by touch.
Four Wheel Disc Brakes Let Down By Poor tires
The brakes gave good progression in response to extra load, and for applications in normal driving, pedal loads were light. When measuring maximum efficiency the wheels tended to lock a little too easily, giving a limit of only 0.9g as the best obtainable on dry roads when tested. As is often the case with an all-disc system, there was no fade in repeated tests from speeds as high as 70 mph; instead, the pedal load necessary actually reduced as the brakes became a little keener with the initial heat build-up.
The handbrake was an unusual pull-out ring mounted on the right of the facia, which operated small brake drums at the rear wheels, within the hub of the disc. With a firm pull it held the car on 1 in 3 gradient. Left-hand drive cars had a foot-operated parking brake. There was also a positive transmission lock, and the front and rear hydraulic circuits were divided.
Continental Record tires were fitted as standard, and several road-testers of the day commented that they felt these were the reason for slightly below-standard maximum braking efficiency. They also allowed a form of aquaplaning wheelspin even in top gear which was not ideal. Lateral grip was much better and the car was controlled very easily in the wet. It was very hard indeed to make the back end slide, and when it did let go it drifted out progressively so that it could be easily checked with the steering.
Ride comfort with the new rear independent suspension was outstanding. Reacctions felt on bad surfaces were short, lively ones, without any pitching or wallow. Poor road surfaces were ironed out so well that, from inside the cabin, it felt as if they could almost have been relaid.
Handling That Inspired Confidence
Cornering was very predictable and inspired confidence. The car understeered quite strongly, and the back of the car seemed to dig in much better than previous models. The optional power-assisted steering reduced steering effort to very reasonable proportions without making it feel dead and lifeless. Drivers could be excused for not knowing there was power assistance because it behaved so unobtrusively; only the much reduced effort, ease of parking, and a slight twitch of the wheel occasionally on starting the engine, revealed that it was fitted. It could have been more precise when running straight, but good directional stability disguised any free play present.
Class Leading Safety
Extreme care had been taken over passenger safety. There was thick, strong padding at the top and bottom of the facia. The door handles were recessed, and circular handwheels opened the quarter vents. Extensive care has been taken over safety in the design, including padded vizors, safety mirrror with knock-out mounting, pliable material for knobs and switches, and neat recessed door handle triggers.
In fact all the knobs and switches were designed with safety in mind, even the ignition key! Small, easily worked child safety catches were accessible when the rear doors are opened, to put the interior catch out of action. A new refinement simplified the bundle of keys which used to be necessary. Finally Mercedes provided one key (with a square head) which worked all the locks on the vehicle. Another key was supplied, which had a rounded head, and fitted everything except the boot, which could be kept locked when the car was left in an attendant's care.
Inside The Cabin
Mercedes had traditionally fitted seats with very firm upholstery, which seem to lack the expected comfort when first sitting in them. The correct shaping of cushion and squab however would prove their worth on a long trip, leaving you in little doubt that the seates were in-fact much better than first impressions gave. Occupants would feel relaxed and free from any aches or discomfort even after a day at the wheel.
The interior trim lacked any pretence of opulence or luxury, but the materials used were durable and very efficient. Seat height, particularly in the front, was a little lower and not adjustable at the front edge as it had been on the previous 250SE, but the reduced scuttle height compensated and gave a commmanding all-round view, with both the squared-up wing crowns in view from the driving seat. A circular speedometer, with numerals every 20 mph, and including a trip mileometer, was matched by a dial on the left containing fuel, oil and temperature gauges. A Kienzle clock was mounted between the two main dials.
Tank capacity was 14.3 gallons. A warning tell-tale would light up abruptly when just over a gallon remained. On the road consumption would vary between 15 and 20 mpg depending on the type of driving. Revised ventilation had fresh air vents in the centre of the facia, with vanes adjustable both vertically and laterally, for cooling face or upper body. A separate control governed volume, and there was a booster for keeping the cool air supply going at low speeds.
Quite separate was the heater, with control markings which were a little confusing until explained. Upper slides, with blue arrows for identification, adjusted air flow separately for screen (left lever) and foot level (right). Beneath the two levers are others marked in red which progressively adjust temperature of the incoming air on each side inndependently. There are also adjustable nozzles with individual controls at each end of the facia, which pass air from the main heater. In winter these effectively demisted the side windows, and in the summer could used for additional fresh air. Positive extraction at the rear took air over the back window and kept it clear of conndensation.
The number of minor controls and switches fitted was reduced by clever sharing and combining of functions. The lighting switch offered no fewer than seven positions. Fog-lamps were standard and were quite effective. The dipswitch was on the column, combined with indicators and headlamp flasher stalk. Pushed in, this same lever switched the wipers on or off, and on the face of the knob was a tiny rocking switch to set fast or slow speed for the wipers.
In the usual Mercedes way the blades overrlapped in the centre of the screen leaving only small triangles uncleared at the lower corners. Pressure on a foot-pedal operated the washers, and worked the wipers as long as the pedal was held down.
The new 114 250 continued the high standards of construction for safety and durability which had become traditional from Mercedes-Benz. It had lost only a little of the 250SE's perforrmance, and made up for it by being even more manageable and comfortable, almost as roomy, cheaper and, in most opinions, considerably better looking.