TYRE TALK
Everything you wanted to know about tyre safety but were afraid to ask!
Tyre Pressure
By ensuring that your car's tyres are kept inflated to the manufacturer's recommended tyre pressure levels, you can extend the life of your tyres, improve the handling of your car, enhance safety and maintain the optimum fuel efficiency.
Tyres which are over or under inflated will affect the handling of your car and may cause the tyres to overheat. This will cause your tyres to wear out quicker than if you had kept the pressure at the correct level.
Where do I find the correct tyre pressure for my car?
This information can be found in the user manual of the vehicle but is also usually printed on a sticker located inside the driver’s door jamb. Failing that you can also look up your tyre pressure online although be aware that no website will take responsibility for giving you the correct tyre pressure for your vehicle, so if you are not sure then contact SmarTTyres. It is also written on the tyre itself.
Overinflated Tyres
If you overfill your tyres, the handling of the car will be compromised as the tyres have to swell to take in the extra air. Over-inflation actually has the effect of reducing the contact area where the tyre touches the ground.
Increasing the tyre inflation without increasing the load in the car will reduce the vehicle handling most significantly in corners. The optimum tyre pressure is normally the one designated by the car manufacturer.
A few years ago there were stories about how you could overinflate the tyres of your car and gain some fuel economy but the prospect of losing any handling of your car certainly outweighs any fuel economy benefits.
Overinflated tyres will wear in the centre more than any other area
Underinflated Tyres
Underinflating your tyres will mean you use more fuel and increase the tyre wear and tear as more of the tyre is in contact with the ground. Driving with your tyre pressures set 10% lower than the recommended level will increase the fuel consumption by up to 5%. The tyres themselves will wear out up to 30% faster than if you had kept them at the right level (as evidenced by experiments performed by Shell Laboratories).
Underinflated tyres will wear on the edges more than any other area
When should I check my tyre pressures?
You should check your tyre pressures at least twice a month and definitely before a long trip. The best time to check your tyres is when they are cool, as hot air expands and can give you a false reading on a gauge. Beware: The gauges at local petrol stations are usually not calibrated, so you can get varying readings. This is another reason to plan ahead with a SmarTTyres Tyre Pressure Monitoring System.
Tyre Safety
Having the correct tyres in the right condition goes without saying. It is important to regularly check your tyres for wear and tear. Makes sure you remove stones or other objects that might get embedded in the tread.
The legal minimum tread depth is 1.6mm throughout a continuous band comprising the central three quarters of the breadth of the tread and round the entire outer circumference of the tyre.
Valves
A new valve should be fitted when replacing tubeless tyres. You also need to check that the valve doesn't leak.
Spare Tyres
Unless you are using run flat tyres, your vehicle will probably have a spare tyre or space saver. Often these are a different size, have restrictions of use and are only there to get you to the next garage. Do not exceed 80 kph per hour with a space saver tyre.
Stopping Distances
Bringing your car to a complete halt takes time. It takes time for you to react to a braking situation, and it takes time for your car to respond to your braking actions. While it is true that advances in brake technology make it easier to stop more quickly and safely than ever before, factors such as weather and road conditions, along with the condition of your tyres can greatly affect your actual stopping distance.
Typical stopping distances
In dry weather on a standard road surface it is expected that a car travelling at 22kph will take 12 metres or 3 car lengths to come to a standstill. This is made up of 6 metres thinking and reaction time, plus a further 6 metres of braking time.
For other speeds stopping distances are as follows:
38kph - 9 metres thinking & reaction time + 14 metres braking time. Total 23 metres (6 car lengths)
64kph - 12 metres thinking & reaction time + 24 metres braking time. Total 36 metres (9 car lengths)
80kph - 15 metres thinking & reaction time + 38 metres braking time. Total 53 metres (13 car lengths)
96kph - 18 metres thinking & reaction time + 55 metres braking time. Total 73 metres (18 car lengths)
112kph - 21 metres thinking & reaction time + 75 metres braking time. Total 96 metres (24 car lengths)
In wet conditions these distances are doubled. To stop from 80kph on a wet road it'll take you almost the entire length of a full-size rugby field to come to a complete halt. On an icy road stopping distances should be multiplied by a factor of 1O!
Tyre Condition
The depth of your tyre tread has a significant impact on stopping distances. New car tyres are typically supplied with a tread depth of about 8mm. A partly worn tyre that is reduced to 5mm of tread depth increases your stopping distance by about 14%. At a tread depth of 3mm that margin goes up to 30%, and on the legal limit of 1.6mm it adds as much as 60% to your actual stopping distance.