Run-flat tyres – convenient or costly? A driver’s perspective.

Picture this: a rainy night on a busy freeway, a cavernous pothole concealed by darkness and the deluge, and an unsuspecting journalist in a new Mini John Cooper Works (JCW) equipped with low profile run-flat tyres. Impact is jarring as the JCW’s Pirelli PZeros plow through the wheel-barrow sized cavity and I pull over immediately. It’s a blowout, surely? No tyre could survive that. 

An anxious inspection in the downpour reveals no issues and back in the car, the vehicle’s tyre pressure monitoring system (TPMS) shows green ‘you’re fine’ lights. But it’s a ruse. 10 kilometres on and two potential exit ramps later, I’m once more pulled over on the side of the freeway – but this time with a completely deflated run-flat tyre and a three hour wait for a tow truck. 

I’ve become one of the growing number of Australians who have fallen victim to the run-flat paradox: when a feature designed to increase convenience actually costs you time and money you haven’t planned for

 

What are run-flat tyres?

 

A run flat tyre has a stronger sidewall structure and, if punctured is claimed to be able to continue running at a maximum speed of 80km/h to adequately support your vehicle for approximately 40kms – allowing you to limp to a tyre store or your local dealer to have it repaired. 

The feature allows manufacturers to jettison spare tyres and toolkits from their vehicles, gifting the driver more boot space, less sprung weight and theoretically, less hassle. 

But run-flat tyres, like those snugly hugging my Mini JCW’s wheels, are a double-edged sword. 

With no spare, once they are flat or blow-out, you are stranded. And while they remain inflated, how are you to know you have a puncture in the first place? 

All I can say is, don’t expect your TPMS to alert you.

 

Tyre Pressure Monitoring Systems.

 

In Australia, “a vehicle equipped with run flat tyres must be fitted with an onboard Tyre Pressure Monitoring System (TPMS) to inform the driver if the tyre has a puncture.” 

But it is important to point out that ‘pressure monitoring’ does not mean ‘puncture detection – and the two types of TPMS: direct and indirect, function very differently.

A Direct TPMS uses tyre pressure sensors placed within the pressurised pocket of your tyre to monitor air pressure within the tyre and transmit the information to the car’s on-board computer. In the event of low pressure (usually 25% below the manufacturer’s recommended level) a warning light will appear on your car’s dashboard. 

An Indirect TPMS does not rely on any hardware or wizardry in the actual tyre, and instead uses the car’s anti-lock braking system (ABS) to monitor lost air pressure in the tyres. The ABS wheel-speed sensors track the rotational speed of each tyre. If one of the tyres is out of sync with the others, it is an indication that the tyre’s air pressure is low. This information is then sent to the car’s computer system and an alert displays on the dashboard.

My Mini JCW (like most BMWS now equipped with run-flats) has an indirect TPMS, and over the 10kms I kept driving, the system clearly was not getting the data it needed to alert me to the catastrophic damage inflicted by the potent pothole. (Though, even when my run-tyre eventually blew out, my car’s indirect TPMS glowed green at all four corners of the vehicle.) 

It really does beggar the question: if an indirect TPMS needs time and distance to do its job, how long can you safely drive on your run-flats once a puncture is detected? The answer varies on a case-by-case basis, but the reality is that flat or low-pressure tyres can impact on your vehicle handling, braking distance and tyre wear – and they can be extremely dangerous, so you should have them inspected by a tyre expert as soon as your TPMS gives you a warning signal of low pressure.

 
 

The professional perspective

 

The tyre experts at Mobile Tyre Shop are quick to put run-flat tyre  technology into perspective. 

“The safety equipment on most modern vehicles is exceptional, and run flat tyres certainly match their inner-tubed counterparts for safety and performance on the road,”  Travis Osborne, Founder and CEO assured me. 

“Certainly, our data suggests that the owners of the modern vehicles equipped with run-flat tyres (which are predominantly from brands like BMW, Mercedes-Benz, Audi, but includes some models from manufacturers like Lexus and Jaguar) are doing direct replacements when it comes time for their first tyre change. Most people seem to prefer them once they’ve had them.”  

If you’re weighing up the pros and cons of fitting run-flat tyres on your car, or wondering whether your vehicle is fitted/can be fitted with a TPMS in order to ensure they are legal, it would be wise to give the Mobile Tyre Shop Team a call.

For my part, and rewinding to that rainy night, the jury’s out . A severe blowout meant my Mini’s run-flat heroics only bought me a few uncertain moments before the tyre lost all pressure. And with no spare wheel stashed in the trunk and no toolkit to demonstrate my fixing prowess, my frustrations were as real as the rain pelting down on the deserted roadside.

The industry’s move towards run-flat tyres and TPMS symbolises progress, promising safety and efficiency. Yet, the fine print reveals the fine line between convenience and vulnerability.

As I sat here, pondering the relentless downpour and my run-flat tyre misadventure, I couldn’t help but question whether, in the pursuit of innovation, we’ve unintentionally ushered in a new era of road-bound uncertainties.

 
 

 

Got questions about run-flat tyres or Mobile Tyre Shop? Get in touch. 

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