What causes a tyre to explode?

Damage: Potholes can cause major tyre damage that motorists would be unable to see.
Damage: Potholes can cause major tyre damage that motorists would be unable to see.© STV

While it is not clear what caused the incident which lead to the death of Jenna Wilcox, motoring experts say many drivers are putting themselves at risk of accident or injury as a result of tyre damage.

While, it is incredibly rare for a person to be injured while holding an exploding tyre, badly cared for tyres are common and can lead to very serious accidents.

The 'explosion' of a tyre is actually not altogther unusual. Most of the time it would be referred to as a blow out, or even a puncture.

The cause is most often something mechanics refer to as an impact fracture.

The part of a tyre which can be seen to the eye is merely a rubber exterior. Inside the rubber is the wheel casing and the casing can easily be damaged without there being any visible evidence.

Something as simple as hitting a large pothole or kerb can cause damage to the casing which would be both invisible to the eye and unnoticable to the driver.

In fact, damage to the casing would not even be picked up by an MOT, as the tyres are not removed during testing. Mechanics look for bubbling, cuts or tread damage on tyres, which can indicate possible casing damage. However, removing the tyres is a costly and time consuming process which is not an essential part of the test. As a result, minor casing damage can go unnoticed, even after an MOT.

Minor impact fractures are unlikely to cause any initial problems, However, the damage can worsen over a period of five or six months, eventually causing the tyre to weaken.

Sometimes, this will result in the tyre blowing out or going flat. On other occassions, it could become noticible to the driver that there was a problem with their tyre. Either way, the damage could lead to accidents and motorists are advised not to rely on appearance to know if their tyres have been damaged. A driver who hits a pothole or a kerb hard should have their tyre checked by an expert to ensure no casing damage has been caused.

In addition, drivers must ensure their tyres meet the following minimum legal safety requirments:

  • All tyres on a car must be compatible and in good physical condition.
  • Tyres must be correctly inflated to the manufacturer's recommended pressure.
  • Tread depth must be above the legal minimum of 1.6mm around the entire circumference and across three quarters of the tyre width.

There is no legal requirment for motorists to carry a spare tyre, however, some roadside assistance firms insist their members keep a spacesaver in their boot.


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