| Location | Douglas, Isle of Man |
|---|---|
| Major events | RAC Tourist Trophy |
| Length | 37.52 mi (60.39 km) |
| Turns | 219 |
| Race lap record | 1 hour 32 mins, 32.2 sec (57.70 mph) (Major Henry Segrave, Sunbeam, 1922) |
TheFour Inch Course was aroad-racing circuit first used for the1908 Tourist Trophy Race for cars,[1] held on public roads closed for racing by an Act ofTynwald (the parliament of the Isle of Man). The name of the course derives from the regulations for the 1908 Tourist Trophy adopted by theRoyal Automobile Club, which limited the competitors' engines to a cylinder-diameter of four inches. The Four-Inch Course was adopted by the Auto-Cycle Club for the1911 Isle of Man TT Races. The Four-Inch Course was subsequently known as theSnaefell Mountain Course or Mountain Course when used for motor-cycle racing.
The new course length was 37.5 miles (60.4 km), based on the 'Short'Highroads Course with the omission of theSandygate Loop and thePeel Loop. The start-line was moved from the road junction of theA2 Quarterbridge Road/Alexander Drive toHillberry Corner on the A18 Mountain Road.
The Four Inch Course was based on a number of public roads closed for the duration of racing, including:
The Four Inch Course was adopted by the Auto-Cycle Club for the1911 Isle of Man TT Races and the start-line was moved to a level section of theQuarterbridge Road between Selborne Drive and the 1st Milestone/Alexander Drive, becoming known as the Snaefell Mountain Course when used for motorcycle racing.[2]
From the1920 Isle of Man TT races, changes were made to the Snaefell Mountain Course and competitors turned left atCronk-ny-Mona following the primary A18 Bemahague Road toGovernor's Bridge, then to a new start/finish line on Glencrutchery Road which lengthened the course from the pre-World War I length of 37.50 miles (60.35 km) to 37.75 miles (60.75 km).
More changes to the course followed for the1923 Isle of Man TT races with the adoption of two small sections of private road betweenParliament Square andMay Hill in Ramsey. The Snaefell Mountain Course had previously negotiated theA2 Albert Road and Tower Road in Ramsey which differed from the original Four-Inch circuit which had incorporated these sections of private road and the new Mountain Course length increased to 37.739 miles (60.74 km). The official course distance for the Snaefell Mountain Course was amended for the1938 Isle of Man TTraces to 37.73 miles (60.72 km) which is the current Snaefell Mountain Course length.[3]
54°10′18″N4°29′31″W / 54.17167°N 4.49194°W /54.17167; -4.49194