What factor primarily causes hydroplaning?

The primary factor that causes hydroplaning is when the depth of water on the road exceeds the tread depth of a vehicle's tires. Hydroplaning occurs when a layer of water builds up between the tires of a vehicle and the road surface, leading to a loss of traction. If the water is deeper than what the tire tread can displace, the tires cannot make contact with the road, resulting in a loss of steering control and braking ability.

The tread on a tire is designed to channel water away from the contact patch with the road, but this is effective only to a certain extent. When that effective limit is surpassed, hydroplaning becomes a risk. It is essential for drivers to understand that maintaining appropriate tire tread depth and being cautious in wet conditions can significantly reduce the likelihood of hydroplaning. Other factors like speed, weight, and road incline may influence driving dynamics but are not the primary causes of hydroplaning itself.