BMC ADO17 - Development

Development

It was developed at BMC as the large-car follow-up to the successful Mini and Austin 1100 under the ADO17 codename. Additional badge-engineered Morris 1800 and Wolseley 18/85 variants were launched, in 1966 and 1967, catering for BMC dealerships selling these marques, and their loyal customers.

The car was unconventional in its appearance in 1964, with its large glasshouse and spacious, minimalist interior including leather, wood, and chrome features plus an unusual instrument display with ribbon speedometer and green indicator light on the end of the indicator stalk. There was a chrome "umbrella handle" handbrake under the dashboard parcel shelf, and the two front seats met in the middle and could be used, on occasion, as a bench seat. Both Alec Issigonis and Pininfarina worked on its exterior. The technology "under the skin" was also unconventional and ahead of its time, including Hydrolastic suspension and an example of inertia-controlled brake proportioning, in the form of a valve which transferred braking force between front and rear axles as a function of sensed deceleration rather than as a function of fluid pressure. The bodyshell was exceptionally stiff with a torsional rigidity of 18032 Nm/degree, this was greater structural rigidity than many modern cars up to the end of the century.

Progressive improvement was a feature of most cars in this period, but the number and nature of the changes affecting the early years of the Austin 1800 looked to some as though the car had been introduced without sufficient development work. A month after its launch, in December 1964, reclining front seats and the option of an arm rest in the middle of the back seat were added to the specification schedule. A month later, in January 1965, the final drive ratio reverted to the 3.88:1 value used in the prototype, from the 4.2:1 ratio applied at launch: this was described as a response to "oil-consumption problems": January 1965 also saw the indicator switch modified. At the same time, higher gearing and reduced valve clearances cut the published power output by 2 bhp but cured the "valve-crash" reported by some buyers when approaching top speed on one of Britain's recently constructed motorways. The manufacturer quietly replaced the "flexible, flat-section dipstick" which, it was said, had caused inattentive owners to overfill the sump after inserting the dipstick back to front so that the word "Oil" could not be seen on it. Subsequent modifications included changing, repositioning and re-angling, the handbrake in October 1965, removing the rear anti-roll bar and rearranging the rear suspension at the end of 1965, at the same time adjusting the steering to address a problem of tire scuffing, and fitting stronger engine side covers in January 1966 along with modified engine-mounting rubbers which now were "resistant to de-bonding". February 1965 saw water shields fitted to the rear hubs and the car's steering rattle cured by the judicious fitting of a spacer, while the propensity of early cars to jump out of first and second gears was addressed by the fitting of a "synchronizer". Further improvements followed the launch of the Morris 1800 early in 1966. Gear cables were revamped to deal with "difficult engagement" of first and third gears in cold weather, and the seat mountings were adapted to increase rake in May 1966.

In June 1967, without any fanfare of press releases, a modified version of the 1800 started turning up in domestic market show rooms with repositioned heater controls, a strip of 'walnut veneer' on the fascia and separate bucket seats replacing the former split bench seat at the front. Various other criticisms seem to have been quietly addressed at the same time, including the announcement of more highly geared steering which now needed only 3.75 rather than 4.2 turns between locks, although the actual modification had applied to cars produced since September 1966 (and, in the case of Australian cars, some time before that). This was also the point at which the car received a differently calibrated dipstick, giving rise to rumours that engine problems on some of the early models had resulted from nothing more complicated than the wrong calibration of the dipstick causing the cars to run with the wrong level of engine oil; the manufacturers insisted that the "recalibration" of the dipstick was one of several (unspecified) modifications, and urged owners not to use the new dipsticks with older engines.

The Mark I's doors were later used on the Austin Maxi and larger Austin 3-Litre (ADO61) model.