Triumph does not build many cars like the Triumph 10/20: a 2-seat tourer, 4-seat tourer, fabric saloon with 1393 cc side valve I4, built from 1923 the vintage years, when coachbuilders still shaped most of what was sold.
The background
The Triumph 10/20 is a car manufactured from 1923 until 1926 by the Triumph Motor Company. It was the first Triumph automobile and was named the 10/20 for the Royal Automobile Club's taxation class of 10 horsepower rating and its actual output of 20 brake horsepower. The design was principally by Arthur Alderson assisted by Alan Lea and Arthur Sykes who were employed by Lea-Francis, to whom Triumph paid a royalty on every car made. It was powered by a 1,393 cc (1.4L) 4-cylinder side-valve engine designed by Harry Ricardo and fitted with a single updraught Zenith carburettor. The engine produced 23.5 brake horsepower (17.5 kW) at 3000 rpm, giving the car a top speed of 52 mph (84 km/h) and economy of 40 miles per imperial gallon (7.1 L/100 km; 33 mpg‑US). The four-speed gearbox was mounted centrally and coupled to the engine by a short drive shaft.
The car was launched as a 2-seat, steel panelled, open tourer with provision for a third passenger in a dickey seat, utilising bodywork supplied by the Regent Carriage Company of London. A sports model with aluminium body panels and long wings soon followed, and then in 1924 a fabric-covered 4-seat Weymann saloon featuring a single door on the driver's side and two doors on the passenger side. It had a 102-inch (2,591 mm) wheelbase, making it the largest (by 20-inch (508 mm)) of the "light cars" of its era. It was the first British production car to be fitted with hydraulic brakes, but at first on the rear wheels only. Approximately 2,500 of this model and the parallel 13/35 and 15/50 models were made. The price was £430 to £460,
The engineering
Under the skin sits 1393 cc side valve I4. Kerb weight is 864 kg. The gearbox is a Four-speed manual. The wheelbase is 102 in. These are manufacturer figures carried by Wikipedia and Wikidata, not road-test measurements.
Where it sits
Where it sits in Triumph's history is not in doubt: the none came before it; the Triumph 13/35 followed it. On a showroom list of its day it stood against the Alfa Romeo P1, the Renault KZ, the Renault KJ. Its Triumph stablemates include the Triumph SD2 and the Triumph Renown.
The money
There is no federal ownership record for the Triumph 10/20 — it predates the complaint database or was never sold in the United States — so MotorJury publishes no running-cost figure for it. For a car of this age the price is set by the collector market and the condition of the individual example, not by a formula.