Thornycroft continued with its 1906 models for 1907, with the exception of the 4,650cc 24hp, which was replaced by the 5,213cc 30hp, another large "four" with the, by now, well-tried in-line, T-head layout. The 30hp car retained the LT ignition system of its 24hp predecessor. Thornycroft entered two cars for the 1907 Isle of Man TT Race, a 14hp with improvements following the previous year's technical problems, and a 30hp in the heavy car event. The 14hp reportedly ran well during pre-race trials round the course, but not much is known of the car's showing during the race. The 30hp car ran out of petrol during the heavy car race, and the rules prevented replenishment.
This magnificent 1907 30hp car is in working order and is owned by HMAS. Photo Nick Corrie.
Offices and showrooms were opened in Albemarle Street in London's West End, to tap into the wealthy London society market. Not satisfied with 6,975cc, Thornycroft enlarged its big "six" by nearly a litre for 1908, to a massive 7,819cc, and introduced the car as the 45hp.
This enormous engine gave around 45bhp at 1,000rpm and, like all other Thornycroft car engines, was an in-line water-cooled engine. The 45hp had a four-bearing crankshaft and unlike the 36hp, its cylinders were cast in pairs, with a noticeable gap between each pair to allow for the two intermediate main bearings.
45hp six-cylinder Thornycroft chassis
Other cars for 1908 comprised the 30hp, continued from the previous year, and the new 18hp which was an improved 14hp with the same 2,715cc capacity. Perhaps the most interesting 1908 cars were the three four-inch racing cars built to compete in the TT Race. Two of the four-inch cars had three-speed gearboxes with direct-drive top, while the other a four-speed all-indirect box. Tom Thornycroft's car came fifth in the TT at 44.1mph (71kph). Much bigger than the 14hp cars entered for previous TT events, the four-inch cars' 4,119cc four-cylinder engines gave 46bhp at 2,000rpm - about double the rpm of Thornycroft's touring cars, so the four-inchers were highly tuned in comparison. From this year on, all Thornycroft cars had HT ignition.