<P> From 1911 the Isle of Man TT transferred to the much longer Snaefell Mountain Course of 37.40 miles (current length 37.73 miles). The race programme developed from a single race with two classes for the 1907 Isle of Man TT, expanding in 1911 to two individual races for the 350cc Junior TT motor - cycles and the Blue Riband event the 500cc Senior TT race . The race did not take place from 1915 to 1919 due to the First World War . It resumed in 1920 . A 250cc Lightweight TT race was added to the Isle of Man TT programme in 1922 followed by a Sidecar TT race in 1923 . </P> <P> There was no racing on the Isle of Man between 1940 and 1945 due to the Second World War . It recommenced with the Manx Grand Prix in 1946 then the Isle of Man TT in 1947 with a greatly expanded format that included the new Clubman's TT races . The Isle of Man TT became part of the FIM Motor - cycle Grand Prix World Championship (now MotoGP) as the British round of the World Motor - Cycling Championship during the period 1949--1976 . Following safety concerns with the Snaefell Mountain Course and problems over inadequate' start - money' for competitors, a boycott of the Isle of Man TT races occurred from the early 1970s by many of the leading competitors, motorcycle manufactures and national motorcycle sporting federations . It is still billed in popular culture as the most dangerous motorsport event in the world, with over 250 fatalities in its history . An on - site account of the 2003 race by Sports Illustrated writer Franz Lidz called the spectacle "38 Miles of Terror...a test of nerves and speed that may be sports' most dangerous event ." In 1976, the Isle of Man TT lost its world championship status and was transferred to the United Kingdom by the FIM and run as the British Grand Motor - Cycle Grand Prix for the 1977 season . The Isle of Man TT Races then became an integral part of the new style TT Formula 1, Formula 2 and Formula 3 World Championships between 1977 and 1990 to develop and maintain the international racing status of the Isle of Man TT races . The event was redeveloped by the Isle of Man Department of Tourism as the Isle of Man TT Festival from 1989 onwards . This included new racing events for the new Isle of Man TT Festival programme including the Isle of Man Pre-TT Classic Races in 1989 followed by the Isle of Man Post-TT Races from 1991 and both held on the Billown Circuit . In 2013, the Isle of Man Classic TT was developed by the Isle of Man Department of Economic Development and the Auto - Cycle Union for historic racing motorcycles and along with the Manx Grand Prix now forms part of the' Isle of Man Festival of Motorcycling' now held in late August of each year . </P> <P> Motor racing began on the Isle of Man in 1904 with the Gordon Bennett Eliminating Trial, restricted to touring automobiles . As the Motor Car Act 1903 placed a speed restriction of 20 mph (32 km / h) on automobiles in the UK, Julian Orde, Secretary of the Automobile Car Club of Britain and Ireland approached the authorities in the Isle of Man for the permission to race automobiles on the island's public roads . The Highways (Light Locomotive) Act 1904 gave permission in the Isle of Man for the 52.15 - mile (83.93 km) Highroads Course for the 1904 Gordon Bennett Eliminating Trial which was won by Clifford Earl (Napier) in 7 hours 26.5 minutes for five laps (255.5 mi or 411.2 km) of the Highroads Course . The 1905 Gordon Bennett Trial was held on 30 May 1905 and was again won by Clifford Earl driving a Napier automobile in 6 hours and 6 minutes for six laps of the Highroads Course . This was followed in September 1905 with the first Isle of Man Tourist Trophy Race for racing automobiles, now known as the RAC Tourist Trophy and was won by John Napier (Arrol - Johnston) in 6 hours and 9 minutes at an average speed of 33.90 mph (54.56 km / h). </P> <P> For the 1905 Gordon Bennett Eliminating Trial it was decided to run an eliminating trial for motorcycles the day after for a team to represent Great Britain in the International Motor - Cycle Cup Races . An accident at Ramsey Hairpin forced out one of the pre-race favourites and the inability of the motorcycle competitors to climb the steep Mountain Section of the course forced the organisers to use a 25 - mile (40 km) section of the Gordon Bennett Trial course . This ran from Douglas south to Castletown and then north to Ballacraine along the primary A3 road and returned to the start at the Quarterbridge in Douglas via Crosby and Glen Vine along the current Snaefell Mountain Course in the reverse direction . The 1905 International Motor - Cycle Cup Race for five laps (125 mi or 201 km) was won by J.S. Campbell (Ariel) despite a fire during a pit stop in 4 hours, 9 minutes and 36 seconds at an average race speed of 30.04 mph (48.34 km / h). </P>

Where is the tt isle of man held