top of page
Armstrong Siddeley 18hp

Following the 1920 motor show it was quickly apparent that John Siddeley had found a winning formula in the new 30HP car. Also he was aware that there was substantial interest from would be purchasers who's pockets were not quite deep enough. So, only 12 months later the 18HP car was launched. Chassis priced at £575 while the complete Tourer was an attractive £670 which made it about the same price as the chassis only version of the larger car. Still not cheap, but of a quality which brought continuing Royal patronage.  Prince Henry, Duke of Gloucester, acquired a 18HP saloon whilst Prince Albert purchased two 18HP cars, one an open sports and the other for state occasions.

Armstrong Siddeley 18hp limusine
Armstrong Siddeley 18hp Mk II 1926 short tourer ex Colin Hope
Armstrong Siddeley 1930 20hp long tourer.jpg

Public awareness was further strengthened by a 10,000 mile day and night trial overseen by the RAC with an 18hp achieving an average 24.5mpg. Today some Club members would be happy with such a return using their later cars.


Technically the car was very much after the design of the larger 30 HP. The engine was a six cylinder bi-block of 2386cc capacity, whilst the wheelbase was 1foot 3inches shorter at 10feet.

Armstrong Siddeley 30hp and 18hp compari

As was common practice at the time braking was accomplished using the rear wheels only. Interestingly these drums contained two sets of shoes. The inner being operated by the foot pedal and the outer by the handbrake. Later cars were fitted with four wheel brakes which had aluminium shoes fitted with friction lining material and operated in large drums all round. These were unusual and certainly the latest technology of the day. Henri Perrot a French pioneer automobile engineer while working for the Argyle motor manufacturing company in Scotland had developed a system which allowed the brakes to be applied to all four wheels by use of either foot pedal or brake lever. This system was patented in America and would be more familiar to us as, Bendix 'servo' braking, not to be confused with modern servo power hydraulic braking. This was 1921 and it shows John Siddeley's awareness of the fast developing automotive engineering industry in that it would take till 1925 before some 50 makes of car had such braking

Armstron Siddeley 18hp short tourer V2 credit CCA.jpg
1927 20 hp 2_InPixio reduced.jpg

We should recall that the 18hp car had opened up a larger segment of the market to Armstrong Siddeley cars and consequently the increased feedback helped shape future policy. Over the next four years the company were busy expanding their range of cars, still maintaining quality, performance and value for money, into the medium size car

market. During this period much useful experience was gained from rallies and publicity events, along with customer and dealer feedback. It is also worth noting that almost half of the Mk1 cars produced were Tourers or Dropheads, this was now giving way to a marked customer preference for saloon cars, a trend which would continue into the 1930's.

So it was in July 1925 that the revamped 18hp Mk II was announced. Significant changes were made to the engine and in two stages to the chassis dimensions. First the engine: now a true monobloc having overhead valves and a removable head. Capacity was increased by 500 cc. to 2872cc. which gave an RAC rating of 20 hp.

Two different chassis lengths were available, the 10ft wheelbase chassis continued on from the MkI version and a new 10ft 9inch wheelbase version was introduced, these were to be known as the standard and short chassis respectively. On both options, the overall body length was increased by 3 inches. This arrangement gave the factory scope for the variety of body types which were to follow. Interestingly, by 1927 the standard chassis had become know as the long chassis, this is the naming custom that we have followed.


Whilst most customers purchased a complete motorcar with a body by the in-house coachbuilder Burlington, a rolling chassis was available for those who wished to have bespoke coachwork from an outside company. 

1926 18hp Van V4.jpg
1927 20hp rear seat Bonhams.jpg
1927 20hp front seats Bonhams.jpg

From mid 1928 the Wilson 4 speed and reverse pre-select gearbox was available for an additional £35. This was a great improvement on the traditional “crash  gearbox” in general use as it eliminated the need to double declutch to achieve a smooth gear change, something many motorists were unable to master. Eventually this type of gearbox became a standard fitting on all Armstrong Siddeley models


This model continued in production until August 1931 when it was replaced by the new 20hp model.

1926 18hp Van 3 2.jpg
1926 18hp Van oside 3 2.jpg
Armstrong Siddeley 18hp Mk II 1926 short tourer ex Colin Hope 130.jpg

Technical Specification

Armstrong Siddeley 20hp Ascot Tourer.jpg
1926 18hp Peel Body 1 2MP.jpg
1929 20hp  Chasiss # 44,351 Australia.jpg

The following images are taken from Armstrong Siddeley's December 1927 brochure, they are all known as 20hp models rather than 18hp Mk II's, they are all produced by Burlington the in-house coachbuilders. It was around this time that Armstrong Siddeley started to give their cars model names, in this case, locations in the British isles. Prices for this model year ranged from £435 for the short chassis Arundel 2/3 seater through to £520 for the Conway Saloon.

Harlech Coupe.jpg
Ascot Open Toure de Lux.jpg
Arundel 2 3 Seater.jpg
Carlisle Threequarter Landaulette.jpg
Chester Enclosed Landaulette.jpg
Conway Saloon Landaulette.jpg
Cotswold Tourer.jpg
Braemare Special Tourer.jpg
Cranwell Fabric Saloon.jpg
bottom of page