A highsider or highside is a type of motorcycle accident characterized by sudden and violent rotation of the bike around its long axis. This generally happens when the rear wheel loses traction, skids, and then suddenly regains traction, creating a large torque which flips the rider head first off the side of the motorcycle or over the handlebars. The initial traction loss may be caused by: New tires with wax or similar compounds on the sides of the wheel, or smooth tire on the edges giving low grip on first usage until the asphalt sands the rubber a little bit Locking the rear wheel through excessive braking Incorrect downshifting technique, producing excessive engine braking (even if the motorcycle has a slipper clutch) Applying too much throttle when exiting a corner Oversteering the bike into the turn by shifting weight to the front wheel and using balance to drift the rear wheel sideways Exceeding the lateral grip through too much speed (although, this is more likely to result in a lowsider), or too much lean An unexpected change in the surface friction (water, oil, dust, gravel, etc.) Reducing the friction on the rear tire by scraping the bodywork, footpegs or stand of the motorcycle on the road surface Highsides differ from lowsides as follows: during a lowside the rear wheel slips laterally and continuously until the bike falls onto its side (the side that's inside the corner), while during a highside the rear wheel slips laterally only briefly before suddenly regaining traction and flipping the bike onto its other side (the side that's outside the corner, and therefore the higher side of the motorbike). As a result, highsides happen very quickly with little, if any, warning and are very violent. If the wheels are not aligned in the direction of travel when traction is suddenly restored and the rear tire stops slipping, then a highside is likely, depending on how much the bike is turned across the direction of travel and how fast the bike is traveling when the rear tire stops slipping. If the angle is high enough, the bike is moving fast enough, and the rear tire slips and regains traction suddenly enough, the rider has no chance of preventing a highside. Technical explanation Forces occurring between the motorcycle and the road (such as those that result in accelerating, decelerating and turning) occur at the contact patch through friction