Keep performing even when the pressure drops: runflat tyres keep you mobile even if all tyre pressure is lost. Instead of an unpleasant and unsafe roadside tyre change, you can reach home safely or drive to the next workshop for assistance.Runflat tyres are their own spares: thanks to specially reinforced side walls and additional lateral strengthening, they continue to perform their function even if all air pressure is lost. The heat-resistant rubber compound is able to withstand additional heat build-up.With runflat tyres fitted, you can continue driving for up to 150 km at a speed of up to 80 km/h without any significant loss in vehicle stability. You not only save time and stress, you are also free of the need to carry a spare tyre, saving stowage space.All driver assistants remain fully functional when driving with a loss of tyre pressure. The optional Adaptive Drive system redistributes the load to the other tyres, reducing the burden on the low-pressure tyre as much as possible.
The wheel rims of runflat tyres have special design that ensures the tyre will not detach from the rim, even on tight bends.Runflat tyres provide greater safety, more peace of mind and additional cabin space. It's not surprising that Germany's ADAC, the largest automobile club in the world, has described runflat tyres as the "first important revolution in tyre design since the invention of the pneumatic tyre." Stay safe while you wait Signs you need new tyres The pros and cons of modern spare wheel tech Why you should avoid cheap tyres What difference does wheel size make? Join us on Facebook Follow us on Twitter Find us on YouTube Find us on Flickr Know your tyres from your wheels Tyres are of course distinct from wheels. Tyres (the rubber outer) are what you fit to wheels (the steel or alloy inner). Wheels are made from either pressed steel or alloy, alloy being aluminium or, on some very expensive vehicles, magnesium. Alloy wheels are lighter so don't impact as much on the car's suspension, and most people prefer them because, well, they just look better.
A wheel's size determines what sort of tyre can be fitted. A good rule of thumb is, the wider the rubber, the better the grip and traction for acceleration, braking and cornering. Most wheel sizes come in inches; when you hear a car has 17-inch wheels, it is referring to the diameter of the wheel. A tyre by any other name Radial tyres have become the standard tyres used today. They provide good handling, especially at high speeds, and efficient grip, especially when cornering. But what about retreads, run-flats, space savers, TUSTs and tyre goo? Are these viable options? The NRMA doesn't recommend retreads or second-hand tyres for a number of reasons, the primary one being safety. "It's not possible to know what sort of life a second-hand tyre has already lived," says Jack Haley, NRMA Vehicle Safety Expert. Retreads, where a new tread is bonded to the tyre case, are better suited to speeds less than 100km/h. At higher speeds, as the tyre warms up, it's possible for the new tread to separate from the case, leading to a blow-out and loss of vehicle control.
Also, retreads often don't meet the manufacturer's specifications for speed and load-carrying. (See 'Tyre Markings' box below.) Some manufacturers use run-flat tyres on many models. The idea is that if you get a puncture, the tyre's sidewall is strong enough to support the car until you're able to get to a tyre fitting station. Run-flats are limited to travel at 80km/h, and have a range of 80 kilometres, enough for you to either complete your journey or travel to the next service point without having to change the flat tyre. An added benefit is that, depending on your vehicle type and use, run-flats can reduce the need for carrying a spare tyre, potentially improving fuel consumption. However, NRMA doesn't recommend using these tyres in remote areas. To use run-flat tyres you must have an onboard tyre pressure monitoring system to warn you when one or more of the tyres are flat, as it's difficult to tell otherwise. Unlike a conventional flat, there is no obvious external signs, such as a flat tyre or the vehicle behaving strangely.
And it's important to know when you do have a flat as you must limit your speed to 80km/h. Also, unlike conventional tyres, run-flats cannot be repaired after a puncture. So you're still up for the cost of a whole new replacement tyre. Space-saver tyres or TUSTs Most models in the new VE Commodore range, from the base Omega to the SS-V and Calais-V, come with a space-saver tyre or TUST (temporary-use spare tyre) as standard. Part of the reason that car makers are moving to a space-saver is that tyre technologies have improved, and we tend not to get as many flats. Car makers are also keen on space savers because they weigh less, which improves fuel consumption, although it is worth noting that the difference between the space-saver and full-sized spare on a Commodore Omega is a mere 4kg. Design is also a factor, and removing a full-sized spare (or removing the spare altogether) gives designers more space for passengers, luggage or both. However, regardless of the trend, Jack says a full-sized tyre is still the only option for people travelling long distances.
And while a space-saver tyre may save you space in your car, it won't save you money, as you will need to buy a full-sized tyre to replace it. Driving around on a space-saver is not an option. It is an emergency spare only and should only be used to get your car to a service centre. Also, like run-flats, they generally should not be driven at over 80km/h. Some car makers offer tyre goo. The idea is that if you get a puncture you connect the tin to the tyre and a sealant is injected through the valve along with a gas that inflates the tyre. However, there are a few major downsides. First, if you have a major puncture, like the sidewall blowing out of the tyre, then the goo is no good. Second, goo also makes it impossible to repair the puncture, leaving you with the cost of a new tyre. So far, goo is confined to the sportscar market, but with car makers trying to shave off every last kilo from their cars in a bid to save fuel, don't be surprised to see it appear with more mainstream models in the future.
Which tyres are for me? The best guide to ensure you fit the correct tyres to your car is your owners manual, or look at the tyre placard on your car. It's normally in the glovebox or driver's-side door jamb. Manufacturers usually design their cars around a set tyre specification, and some may even go so far as to design their cars to work with a particular tyre from a particular manufacturer. The tyre is where the car meets the road, and the car must rely on that connection to the road for braking, steering and traction loads. So, you need to think carefully before changing the wheel and tyre combination on your car - small changes can lead to big compromises in grip, handling and safety. That's why it's always wise to consult a reputable tyre fitting station before upgrading your car's wheels. (NRMA Members receive special offers or discounts from Beaurepaires centres.) Also, fitting alternative wheels and tyres to your car is viewed as a modification, and all major and minor modifications made to your vehicle or its equipment that affect rego details must be reported to the RTA to ensure accurate records are maintained.