What usually causes locked wheel skids?

Locked wheel skids typically occur due to breaking too hard at high speeds. When a driver applies the brakes forcefully, especially when traveling fast, the wheels can stop turning while the vehicle is still in motion. This results in the wheels locking up, leading to a loss of traction. In this situation, the vehicle can slide uncontrollably, as the tires are no longer able to grip the road surface. This type of skid is particularly dangerous as it reduces the driver's ability to steer the vehicle away from obstacles.

Driving on icy roads can contribute to skidding due to reduced traction, but it does not directly cause locked wheel skids in the same way that aggressive braking does. Similarly, turning too sharply can lead to different types of skids, like a lateral skid, but it does not typically result from the wheels locking up. Lastly, while failing to use anti-lock brakes can exacerbate a situation and may lead to locked wheel skids, the primary cause is still the act of braking too hard at high speeds. In essence, the mechanics of locked wheel skids are centered around the braking force exceeding the tires' grip, which is most directly connected to high-speed braking.