The tyres are arguably the most important primary safety feature. They are the only contact between you and the road, and through them you control the vehicle's potential acceleration, braking and cornering forces.
Check tyres regularly
You should get into the habit of checking tyre pressures at least once a month. This is most conveniently done at a service station, but be aware that the gauges at these places can get battered. If the one you use looks a bit worse for wear, go somewhere else or check the pressures against your own gauge (available from auto spares shops).
While checking the tyre pressures, also look for wear or damage. All tyres have inbuilt indicators to show when they are worn too far.
If there is noticeably uneven wear, the wheel may need rebalancing or the steering alignment may be out. Either way, a specialist should check it. If there are splits or damage, it could be time for a new set of tyres.
Day-to-day use of the car quickly causes bits of the tyre to be scrubbed off. Since most cars these days are front wheel drive you’ll likely notice front tyres will invariably wear quicker than the rear.
This is because the front axle on a front-wheel-drive does the majority of the dynamic work of the vehicle’s chassis, including all of the power delivery, about 70% of the cornering forces and up to 90% of the braking forces. All of these forces are delivered through the tyre to the road surface.
The fact that they wear quicker is not in itself significant but what is relevant is how much better a new tyre performs than a worn one. Repeated heating and cooling of a tyre by the forces applied to it eventually affects the structure of the rubber, particularly how it springs back into shape.
Basically the tyre becomes harder, which degrades its grip and makes it much more prone to punctures. This process accelerates as rubber is worn away because there is less rubber to share the heat load. Finally, as a tyre wears the tread also reduces, meaning it displaces less water and so gradually compromising wet-weather performance.
Perhaps no other item on your car is taken for granted as much as the tyres. They are constantly being worked over as we drive but we usually don’t think about them until one goes flat.
The most usual form of tyre neglect is running them at too low a pressure. This causes heavy wear, delivers poor cornering and braking and, worst of all, blowouts, which can be catastrophic.
You might think having a less-inflated tyre means more of it is in contact with the road but actually it’s the reverse. In an under-inflated tyre, the middle section bows up, leaving only the edges touching the road. This concentrates more heat and wear in these areas.
All car makers recommend pressures for the tyres on their cars. These are listed on a little placard usually found inside the driver’s door jamb or the fuel filler cap.
Tips for safe tyres
1. Be wary of service station tyre gauges, consider buying your own quality pocket gauge
2. Check tyre pressures, look for damage and embedded foreign objects every two to three weeks.
3. Tyre pressures cold should never be below the cars placard specification. Slightly higher pressures are strongly recommended for improved grip, response, economy and life.
4. Always use valve caps to exclude dust and water.
5. Rectify the cause of irregular tread wear as soon as possible by consulting an expert. Minimum legal tread depth is 1.6mm across the full tread width.
6. Have wheels balanced and aligned annually.
7. Avoid second hand tyres. Their history is unknown.
Space savers - Temporary Use Tyres (TUTs)
Temporary Use Tyres (TUTs) are temporary use tyres that are not the same size as a vehicle's on-road wheels. They’ve grown from being an alternative in space-starved sports cars to standard issue for anything up to roomy four wheel drives.
All motorists should check their vehicle for the presence of a TUT and familiarise themselves with the limitations of driving with a TUT.
When purchasing a new vehicle, car buyers should:
- seek information from the dealer as to whether the vehicle is fitted with a temporary use tyre: the sales person will probably not raise the issue, and
- consider insisting on a full size spare as a condition of sale if the vehicle is capable of taking a full-size spare.
If you need to use one you should be aware to only drive it for the minimum distance required to repair or replace the damage to the full-size wheel and drive at all times within the conditions specified in owner's manual.
The most widespread TUT type is the traditional space saver tyre. These tyres are prominent due to their reduced size and brightly painted rim.
An 80 km/h speed rating usually applies because of the compromise to the vehicles handling when it is fitted.
Other types of TUTs may even be supplied deflated and folded up into the boot to save more space.
Compromise to vehicle handling
A space saver is not a spare tyre, it is an emergency use tyre designed to allow the car to be driven to a repairer.
A downside to the small size of the space saver spare is that they often have dynamic deficiency during emergency braking, emergency swerving and cornering.
RACV conducted three tests on vehicles from four different market segments to assess vehicle handling when a TUT is fitted. Three involved traditional space saver spare tyres, and one was a smaller wheel spare tyre.
The space saver tyre increased braking distance by 15.4 metres or three and half car lengths when fitted to the front axle.
Cornering traction suffered appreciably when a traditional space saver was fitted; particularly on heavier vehicles such as large SUVs where the deterioration in grip levels was 13.5%.
The International Standards Test for Emergency Lane Change (the "Moose test") indicated that fitting a traditional space saver significantly increased the difficulty of emergency swerving without the vehicle becoming unstable.
RACV testing has revealed that a common type of space saver tyre is only capable of around 450 km of road driving before it becomes un-roadworthy.
Driving on a TUT is acceptable under Victorian roadworthy regulations as long as it is used within the specifications provided by the vehicle manufacturer in the vehicle's handbook. However, two TUTs cannot be fitted to any one vehicle and the vehicle cannot be presented at a roadworthy inspection with a TUT fitted.
Insurance claims involving TUTs are treated like any other insurance claim whereby the contributing factors are determined individually for each case. While TUTs do not automatically exclude claims for approval, the insurer may determine whether the tyre was used within the specifications (e.g. speed requirements, fitment to a specific axle) of the vehicle manufacturer when assessing the claim.