What can cause your trailer to jackknife when backing up?

The scenario where a trailer jackknifes while backing up primarily relates to how well the tractor is able to follow the intended path of the trailer. When the tractor does not effectively align with the trailer’s movement, it can lead to a situation where the trailer swings outwards, creating an angle between the trailer and the tractor. This angle can increase to a point where the trailer pivots toward the tractor, resulting in a jackknife.

This situation is often exacerbated when the driver is not aware of the trailer's position relative to the towing vehicle, leading to improper steering input. It is crucial for drivers to anticipate the motion of the trailer and make steering corrections accordingly. Understanding the mechanics of trailer movement, especially during low-speed maneuvers such as backing up, is key to preventing jackknifing.

Other factors that could theoretically contribute to jackknifing, like heavy trailer loads, faulty brakes, or driving conditions, primarily influence handling characteristics but are not direct causes of the jackknifing motion itself when properly aligning the tractor and trailer.