Tyres with tread under this limit will slide easily, suffer from extended braking distances and will be more susceptible to rupturing. In wet conditions the vehicle will aquaplane, making braking and handling almost impossible. Tyres with tread under this limit are illegal and may lead to a fine or disqualification.

If you drive with low air pressure in your tyre, heat is generated in the tyre. This can result in the rubber and cord separating, which in turn leads to the cord becoming cut and puncturing the tyre. Low pressure can wear the edge of tyre which will shorten the tyre's life.
Excessive pressure results in the tyre becoming unpredictable. If the tyre suffers an impact, it is easily ruptured and cut. If you brake hard, the tyre may skid, which reduces tyre life as the centre of the tread becomes worn.

If you drive with materials such as stone in the tread groove, or with a nail stuck in the tyre, the tyre can become punctured or ruptured. You should change the tyre immediately on discovering any damage to avoid any further damage to the carcass.

In absence of good maintenance, abnormal wear may occur due to sudden braking. You should check air pressures, alignment and rotate the tyres regularly. In addition you should avoid bad driving habits such as sudden acceleration, braking and cornering.

Make sure you regularly check the spare tyre's air pressure, existence/non existence of damage and the depth of remaining grooves regularly.