Four-cross (4X), also called mountain-cross, not to be confused with fourcross, is a relatively new style of mountain bike racing where four bikers race downhill on a prepared, BMX like, track, simply trying to get down first. These bikes are generally either full suspension with 3 to 4 inches of travel, or hardtails, and typically have relatively strong frames. They run a chainguide on front and gears on the back. They have slack head angles, short chainstays and low bottom brackets for good cornering and acceleration. In recent years the tracks raced on have been rougher and less like those used in BMX, this has been met with mixed reaction from riders although is generally believed the move away from BMX will benefit the sport.
The current world champion is Joost Wichman.
Four-cross was added to the UCI Mountain Bike World Cup and the UCI Mountain Bike & Trials World Championships in 2002, replacing dual slalom. It was removed from the World Cup following the 2011 series. A replacement world series, the 4X Pro Tour, was launched in 2012.