It was not only pedals that came under scrutiny for the 1908 races. Fuel regulations were changed and volunteers to act as course marshals were called for.
Singles were restricted to 100 miles to the gallon and twins to 80 miles. After so many brushes with local traffic and, more often, sheep the previous year, it was obvious the St John's Course would have to be marshalled. Once again the Manx government came up trumps by enrolling marshals as special constables, a tradition that has continued until the present day.
The races were held in September alongside the car TT, and the banning of pedals had a significant effect on the development of machinery that had to negotiate the infamous Creg Willey's Hill.
After wet practice sessions the 36 starters were bathed in sunshine as they lined up at St John's.
Fifteen singles and 21 twins made up the increased field, with both German and Swiss riders entering for the first time. There was also new machinery, with two Belgian four-cylinder FN bikes entered in the twin class, but in the singles the Colliers and the Triumph-mounted Marshall continued their battle.
Fowler also returned, looking for a repeat performance on his Norton twin, but like the Colliers he would sail back to the mainland disappointed. Marshall led the singles, but lost ground when he crashed at Kirk Michael on the first lap. He dropped back further to change a broken exhaust valve and mend a puncture, but was determined to beat Charlie Collier and his all-conquering Matchless. Collier also had his problems and had to change a plug, but still led at the half-distance break.
Marshall really got the Triumph flying in the second half and overtook Collier to win by two minutes. His average speed was 40.49 mph – the first 40 mph-plus race average. In third place was Sir R. K. Arbuthnot, who had taken special leave from his Royal Naval duties to compete on his Triumph. Harry Reed won the twin class on his Peugeot-engined DOT after early leader Fowler was forced to retire. Once again the average speed of the winning twin was slower than that of the smaller capacity single.