Get A Grip On The Road
Sydney Morning Herald
Friday October 19, 2007
How far can I drive on a space-saver spare tyre?
Space-saver spare tyres (or, in the industry jargon, TUSTs, or temporary use spare tyres) come in several different shapes and sizes, but they all have severe limitations compared with full-size spares.The car companies fit them because they're cheap, they take up less space in the car and they're lighter. They usually have to be inflated to higher pressures than normal tyres, because they are smaller.The Royal Automobile Club of Victoria's benchmark study on the performance and durability of space-savers found that some have a life of only 450 kilometres or so. The RACV also found that they can be difficult and expensive to replace once they are worn out.However, wear isn't really the main issue. If you get a flat and fit your space-saver, are the cars' handling, braking and steering compromised to the point where it can become unsafe to drive?The short answer is yes. Every space-saver now carries a sticker with a warning that 80kmh is as fast as you should go if you have to fit it.We'd suggest that is probably optimistic. When the RACV fitted space-savers to some test cars and did the same manoeuvres as on a set of full-sized tyres, the results were not pretty.On small cars, braking distances increased between 2.5 and 3.5 car lengths.Cornering grip was reduced by up to 28 per cent, and the cars demonstrated "a significantly reduced ability to pass through the emergency lane change test [a series of quick swerves] without developing oversteer". Oversteer is when the back end of the car loses grip and it can lead to a spin. This is not fun.So if you get a flat and have to fit your space-saver, drive extra carefully and get your full-sized tyre repaired, or preferably replaced, as soon as possible.
© 2007 Sydney Morning Herald
