Driving with under-inflated tyres is dangerous, if the tyre pressure is to low, too much of the tyres surface is in contact with the road, this causes increased friction which can lead to premature wear and tyres overheating.
Over inflated tyres reduce the area of contact with the road, this can affect the vehicles handling and braking. Drivers are at increased risk of aquaplaning and tyres are more susceptible to damage from uneven roads.
Wheel alignment is very important, correctly aligned wheels will stop your vehicle pulling to either the left or right side of the road. Poor wheel alignment will decrease your tyres life span, and may increase fuel consumption.