Anatomy of a Blowout

‘You may be able to detect a slow puncture, but you can’t stop a blowout – they happen instantly!’

It may seem that, when it happens to your vehicle, a blowout is an instantaneous occurrence – something has gone through the wall of your tyre and the whole thing has just gone ‘bang’. However, in reality, the majority of blowouts are not caused by a sudden traumatic incident but are the result of gradual deterioration in the capability of the tyre to retain the air pressure within the tyre walls, resulting in the catastrophic failure of the tyre carcase as a blowout.

A blowout generally starts as a small puncture in the tyre – perhaps caused by driving over some debris in the road, or striking a kerb or obstacle at speed. Over the space of a few miles this puncture gradually causes the tyre pressure to fall as air escapes through the defect, which in turn leads to a gradual decrease in the overall diameter of the wheel and tyre assembly as the pressure within the tyre is not sufficient to resist the downward forces of gravity and loading.  This decrease in overall diameter manifests through increased flexing of the tyre sidewall (think of how a tyre on a vehicle looks when it is partially deflated – it bulges out at the bottom as the weight of the vehicle pushes down), and it is this flexing and bulging that leads to the ultimate failure of the tyre.

As the tyre sidewall starts to flex and return more due to this pressure decrease, excess heat begins to build. As the sidewall becomes excessively hot, the capability of the tyre wall to retain the air pressure remaining in the tyre degrades to the point where remaining air pressure overcomes the sidewall’s capacity to hold it in, and the entire sidewall fails as a blowout.  British motorway hard shoulders are littered with the aftermath of this process – we’ve all seen the near complete hoops of tyre tread that have come from truck tyre sidewalls blowing out, usually as a result of this gradual heating leading to the loss of integrity and final blowout.

This is where TPMS comes in, and can help prevent this series of events leading to a full blowout and subsequent loss of tyre. By identifying that there is a gradual loss of pressure, a feature that is integral to TyrePal’s range of monitoring systems, it is possible to pull over and fit your spare tyre, or call out roadside recovery to help out.  Hopefully, by catching the puncture before it turns into a blowout it will be possible to repair the tyre rather than having to replace it, but even if the tyre is not repairable (for example if the puncture is in the sidewall of the tyre, there is significant damage to the structure of the tyre, or there is a large split or gouge) then by catching the puncture before the sidewall blows out you should be able to bring the vehicle to a stop in a safe and controlled manner, and potentially avoid incurring significant costs due to damage that may be caused by a full blowout.  As an example, there has been at least one case where a tyre has blown out on a caravan, and the remnants of the tyre, amounting to approximately 5kg of steel and rubber spinning around in the wheel arch, snagged the caravan wiring, wrapped it around the axle and stripped the whole wiring system out of the caravan along with all of the cupboards off the walls.

A puncture may merely be an inconvenience, or it may be a significant incident leading to major damage and loss. Whatever the possible outcome, however, TPMS can help minimise the risk of that happening, giving greater peace of mind when driving. Plus, it may be possible that you actually can stop a blowout – simply by detecting that initial puncture that starts the chain of events leading to the total loss of the tyre.