The 1911 Isle of Man Tourist Trophy races took place for the first time over the "Snaefell Mountain Course". The whole organisation of the races was given over to the Auto Cycle Union (ACU), who announced the use of the longer mountain course with a four lap (150 mile) Junior race on Friday 30th June and a five lap (189 mile) race for the Senior race on Monday 3rd July. In only five years the TT races had grown up and commercialism set in.