The Austin 18-24 (or 18-24 hp) was a large 5-litre luxury motor-car produced by the British Austin Motor Company, its successive engines rated around 30 horsepower for tax purposes and the pundits of the day regarded it as really a 30-40. It was launched in 1907 with the 25-30's 5.3-litre (4½ x 5 inches) engine and in Austin's catalogue replaced the 15-20, of which only four were made. The next year it used the 15-20's 4.4-litre engine.
It was in fact replaced for 1914 by the 6.1-litre 30.6 tax horsepower Austin 30 hp. though the catalogue showed a new 20-hp described by the same pundits with the note "20 hp is a very fair estimate of its ranking".
The 18-24 began with the 32.8 tax horsepower 4-cylinder 5.3-litre engine intended for the 25-30 then the following year it was switched to the same 27.3 tax horsepower 4.4-litre (4399 cc) (4⅛ x 5 inches) engine as the short-lived 15-20. Finally the engine was enlarged to 30 tax horsepower and 4.8-litres (4⅜ x 5 inches) for 1911.
Tax ratings 32.8 hp, 27.3 hp, 30 hp.
There was a choice of wheelbase:
- 5.3-litres 1907: 10' 6", 3200 mm
- 4.4-litres 1908-1909: 9' 0" or 10' 6", 2743 mm or 3200 mm
- 4.8-litres 1911-1913: 9' 11" or 10' 8", 3023 mm or 3251 mm
- from their Motoring Correspondent, The Times June 1914
"Among the English firms who have built up a well-merited reputation with one particular type out of their range of models is the Austin Motor Company. For some years they have sold to the public a very sound vehicle in their 18 hp four-cylinder model. It may be said that the 18 hp Austin was one of the historic cars ranking in fame with the old 18 hp Mercedes, the 15 hp Panhard, the 40 hp Rolls-Royce and some others. This car varied slightly in certain details from year to year, but the main characteristics of the type were preserved for a considerable time. It had its faults, but its virtues were sufficiently positive to gain for it a place among the cars of repute." 
- The Austin Car. The Times, Tuesday, Jun 02, 1914; pg. 13; Issue 40539
- David Culshaw, Peter Horrobin, The Complete Catalogue of British Cars 1895-1975, Veloce Publishing, Dorchester UK, 1974 ISBN 9781874105930
- Massed Motor-Car Production. The Times, Saturday, Jun 12, 1920; pg. 11; Issue 42435.
- "Austin: 18-24 h.p.". Grace's Guide. Retrieved 8 August 2012.
- Autocar 10 May 1913
|Austin Motor Company road car timeline|
|Small family car||7 hp||Seven|
|Full-size car||15 hp||Sixteen or Eighteen||Eighteen|
|Coupé / Roadster|
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