Very simply for this achievement, go to SOLO --> QUICKRACE --> Choice the Snaefell Mountain Course, put one Lap, at the end of the race, quit to board and restart the same method 10 times.
He took's me between 20 to 22 minutes for 1 lap, so 4h for the 10 races with the different download.
You have the possibility to cumulate different other achievement.
Good luck !