Tyre age a factor in road safety
MOST Gympie motorists know they need to change a tyre when the tread gets too low, but there is another important safety factor vehicles owners need to be aware of: the age of a tyre.
The Gympie Times received a letter from a concerned reader this week whose caravan tyre blew out despite having plenty of tread left on it.
The reader had purchased his tyres four years ago, but after the blow out he was told by the tyre repairer his tyres were 15 years old.
The Bridgestone website says there are three main mechanisms of tyre aging.
The first involves rubber becoming more brittle.
Sulphur is used to link rubber molecules together during vulcanisation with the application of heat and pressure, giving the rubber its useful elastic properties and strength.
As the tyre absorbs energy in the form of light, heat or movement the tyre continues to vulcanise.
This ongoing vulcanisation causes the rubber to become stiffer and more brittle.
The second mechanism of tyre ageing is oxidation involving oxygen and ozone from the air compromising the strength and elasticity of the rubber and the integrity of the rubber to steel bond.
Basically heat and oxygen cause the rubber to harden and become less elastic.
Thirdly, breakdown of the rubber to steel-belt bond will occur due to water permeating through a tyre and bonding with the brass plate coating on steel belts.
This causes the steel to rubber bond to weaken leading to reduced tyre strength and reduced heat resistance.
If compressed air used for inflation is not completely dry, tyre strength will be affected over time.
Even unused tyres will become more brittle, weaker and less elastic with exposure to water, air, heat and sunlight.
The date of manufacture can be found on the side wall of your tyre.
All tyres are produced with a serial Tyre Identification Number that shows the date of manufacture of a tyre (see picture above).
The last four digits of the serial TIN indicate the week and year that the tyre was made.
For example, the picture above shows a tyre made in the third week of 2010 making it just over a year old and safe to drive on.
Tyre fitters say the tyre most overlooked is the spare and they recommend drivers check the age of their spare tyre before embarking on long journeys.