The World’s Toughest 24 Hour - SXS 24-Hour Endurance Challenge. Invite Only. Limited Entries. No Quit. The World’s Toughest 24 Hour is an elite off-road endurance challenge designed for those ready to push beyond physical, mental, and mechanical limits. Hosted at the legendary Darkwater Trail System at Famous Reading Outdoors, this 24-hour continuous endurance challenge runs day to night [...]