Generally tyres of vehicles are filled with air to absorb the shocks generated as the vehicle moves on uneven roads, and make the ride comfortable.
The shock absorbing capacity is enabled by a fundamental property of air namely compressibility – air gets easily compressed to smaller volumes on application of pressure.
But water is not compressible and so if one uses it to fill the tyres, all the shocks generated on the tyres will be completely passed on to the vehicle and its passengers will feel the discomfort.
In addition water-filled tyres increase the rolling resistance of vehicles because of the increase in weight. Hence apart of the engine’s power and fuel is wasted in overcoming this resistance.
