Regarding hydroplaning and tyre pressure, which statement is correct?

• A. Minimum hydroplaning speed is proportional to the square root of tyre pressure
• B. Minimum hydroplaning speed is proportional to tyre pressure
• C. Hydroplaning speed is independent of tyre pressure
• D. Hydroplaning speed is inversely proportional to square root of tyre pressure

Answer: (A)

Hydroplaning starts when a layer of water builds between the tire and the surface and the tire loses contact with the runway. How easily that water layer can form is influenced by how stiff the tire is, which comes from its inflation pressure. A higher tire pressure makes the tire stiffer and reduces the contact patch, so water tends to get trapped more easily under the tread. To generate enough water pressure under the tire to lift it off the surface, you need more speed. This leads to a relationship where the minimum hydroplaning speed grows with the square root of the tyre pressure. In other words, increasing tire pressure raises the hydroplaning speed, but not linearly. That’s why the correct statement says the minimum hydroplaning speed is proportional to the square root of tyre pressure.