BLOWOUT – Tyre failure facts and fiction

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(By Grant Spolander)


“What a s**t tyre!” A sentiment commonly heard after a tyre failure – usually a few days after you’ve recovered from the thought of nearly dying. It’s a common reaction: the belief that the tyre blew out because it was defective. We’re going to ignore the fact that 99% of all road users don’t take care of their tyres, while conveniently forgetting the countless quality-control standards that govern the tyre trade. Heck, it’s impossible to sell teddy bears in Europe without having pass a thousand health- and safety laws, but sure, defective tyres are running rampant on the roads…


I’m not suggesting that tyre defects don’t occur: they do, but on a level that’s nowhere near the scale of public perception. The fact is, defects are rare, like winning the lottery is rare; and of the genuine cases reported, most are superficial defects rather than structural. But let’s not kid ourselves, tyre failures do happen every day, and the question is: how do you stop it from happening to you?


Let’s answer that question with another question: how often do you inspect your tyres before climbing into your vehicle? I’m guessing ‘never’, right? Of course you don’t, no-one does! I don’t even check mine, and I have a rubber fetish! It’s ironical, because one could argue that tyres are critically more important (from a safety point of view) than any seat belt, airbag, or Euro NCAP rating.



Under-inflation is the number one cause of tyre failures. There are two possible scenarios: The first of which is that the tyre has a puncture and is completely deflated; as a result of this, the wheel-rim rests on the tyre’s sidewall, causing a circular pitch point. This pressed seam invariably ruptures. The evidence of such a blowout is a perfectly neat and circular tear pattern around the tyre’s sidewall. The second scenario is that the tyre was partially deflated (usually due to laziness or poor maintenance), which allowed the tyre’s sidewall to flex (almost like an added suspension component), and thus generate heat (friction) within the tyre material. In this case, the faster you drive, the more the tyre flexes, the hotter and weaker it becomes… and it’s only a matter of time before it ruptures.


Unfortunately, in the case of the totally-deflated tyre, most people don’t realise that they have a puncture, especially if the deflated tyre is at the rear of the vehicle where you can’t feel any steering difference. Or, on a dead-straight highway where there’s no need to turn. Which is why, one of the best investments you can make in your 4x4, is a set of tyre-pressure monitors (TPMS). Admittedly, they’re not cheap; but the system needs to work only once to pay itself off, and potentially save your life.



In truth, the term “blowout” is a bit out dated and refers to previous generation tyres than would instantaneously burst following any sidewall damage. These days, however, tyres can shoulder a remarkable degree of abuse before finally failing; they’re made to such a high standard that failures are seldom instantaneous reactions, but rather, undetected problems that continue to get worse the longer they’re ignored. Theoretically, you could pick up a slow puncture on a 4x4 trail, jump back onto the freeway, and drive 100km or more before the tyre finally gives in.


Lastly, beware of forum “facts”. The internet may be a great source of information, but it’s also where you’ll find the highest concentration of daft tyre testimonials. I once heard a chap complain about his “rotten tyres” because he’d suffered two failures at the same time, not quite simultaneously, but on the same stretch of road. As mentioned before, tyre defects are extremely rare: so to have two defective tyres on the same vehicle would be the chance equivalent of stepping on a winning tote ticket at an Amish church social.


It’s easier to blame the big tyre corporations for producing a poor product, than to consider the fact that we neglect our tyres. So, let’s forget about the “evil” tyre giants for a minute and end off on this point: tyres are your vehicle’s most important safety feature. Abuse them at your own peril, and never ignore them… air is free.

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