Correct tyre pressure will help you get the maximum life from your tyres. It also optimises ride comfort and fuel economy. Warning: driving with uneven pressures on different sides of your car could result in a loss of control when braking or accelerating. The balance of your car is also upset and tyre wear will be uneven.
Over-inflation: An over inflated tyre is simply not capable of sitting squarely on the road. Another undesirable outcome is that normal flexing of the tyre will be reduced and will result in undue wear in the centre of the tread. Over-inflation also makes the fabric pile more susceptible to damage.
Under-inflation: too little air in a tyre produces abnormal deflection in the shoulder area as well as excessive heat build-up. The extra strain increases the risk of fabric damage and separation failures.
Let's simplify it: Keep your tyres properly inflated. The End.
Annoying Vibrations (as opposed to good vibrations)
Poorly balanced wheels can cause your car's steering to vibrate badly as the tyre hops along the road and limits adhesion. This may sound like fun, but it's not. Tyres need to be balanced on their wheels so they run smoothly and wear evenly.
Out-of-balance wheels accelerate wear on the car's suspension joints and shock