Minimum hydroplaning speed is related to tyre pressure in which way?

• A. Proportional to the square root of tyre pressure
• B. Directly proportional to tyre pressure
• C. Inverse to the square root of tyre pressure
• D. Independent of tyre pressure

Answer: (A)

Minimum hydroplaning speed depends on tire inflation pressure because pressure controls how the tire interacts with the water on the runway. As inflation pressure increases, the contact patch becomes smaller and the tire stiffer, making it harder for a thin water layer to force the tire away from the surface. Water must be expelled from under the tire fast enough to prevent a continuous film from forming; with higher pressure, the tire can push water out more effectively, so a higher speed is needed before hydroplaning occurs. The relationship is not linear but follows a square-root trend: the hydroplaning speed increases roughly with the square root of tire pressure. Therefore, the minimum hydroplaning speed is proportional to the square root of tire pressure.