1. Underinflated tyres' sidewalls can get damaged structurally, making the vehicle less stable. 

2. Underinflated tyres are more prone to punctures, bulging and cuts.

3. Unequal air pressure in the tyres can cause strain on the suspension. This can lead to wheel alignment issues, hence further causing wear and tear and handling issues.

4.  Improper tyre pressure may damage the rims when driven over bad roads, especially at high speeds.

5. With low air pressure, the tyre can burst due to heat and pressure build-up. At high speeds, it can be very dangerous.

6. Cornering at high speeds could be troublesome if the air pressure in the tyres is uneven. You may feel the tyre wobble and give out under the vehicle.

7. Steering becomes unresponsive and feels heavier when the car tyre pressure is not proper. It can lead to  a mishap.

8. Underinflated tyres friction between the tyres and the road surface increases if they are underinflated. Therefore, reducing the fuel efficiency of the vehicle and the tyre life too.