Should Tyres have a use-By Date?
Channel 7’s “Today Tonight” program on Friday 5th December, picked up on earlier publicity originating from an American T.V. program “Twenty-twenty”. An aggrieved customer in South Australia complained that he had been sold Light Truck tyres that were already 14 years old when fitted. One tyre had separated its steel belts from the tread ring, causing damage to his mudguard, and raised the risk of an accident.
The British Rubber Manufacturers have recommended that tyres more than six years old should not be sold, but there is no law requiring this anywhere in the world at present. The American Rubber Manufacturers Association states that there is no scientific evidence to support a six-year limitation on the life of a tyre.
The Channel 7 program cut pieces from the sidewall of the tyre, and did a “tensile test”, pulling on the test piece till it broke. Pieces cut from the (used) 14 year old tyre broke at a lower tensile than from a new tyre. Why they tested the sidewalls, which are a different rubber compound to the tread/steel belt area, it is not known, but it is not surprising that testing two tyres made 14 years apart would give different test results. The reason? The tyres were different!
Tyres are warranted for their life by the manufacturer. Occasionally tyres, like many products, are subjected to a recall program. To enable identification of these, a code is branded into the sidewall, which is used world wide, and is a requirement of the American Department of Transportation. It is called the DOT code. Practically all tyre manufacturers worldwide use this code.
The code details the actual factory in which the tyre was made, the design, and among others items, the last appearing group lists the week and year the tyre was made. 3 digits for the ninetees, four digits for the noughties. Examples then are 489 for the 48th week of 1989, 2604 the 26th week of 2004.
Tyres are generally 6 months to 2 years old by the time they are fitted to your car as replacements. The original equipment tyres are generally one week to six months old, dependent on whether the car was made here, or imported.
The Australian tyre market is so fragmented, with many makes and models of vehicles sold, that the supply chain for replacement tyres is very long, and large stocks are held at distribution points to meet market requirements. For example, the 11 hectare distribution centre at Somerton, Victoria, can hold up to 11 million tyres. Naturally, efforts are made through inventory control to ensure quick turnaround of stock going into the store, to reduce holding costs.
Eventually, tyres are shipped out to your local tyre store. Here they should be stored in racks, in a “cool, dry place”. Many tyre storage areas paint their tyre storage area windows with blue paint to screen out U.V. This is because tyres get harder with age. The vulcanisation process continues at a very slow rate, and protective agents such as antioxidants and antiozidants incorporated into the mix diminish in effectiveness with prolonged storage. Walk into a darkened tyre store, and you can smell the rubber. A somewhat doubtful farming practice used to be that tractor tyres were stored by the farmer to “harden them up”, and possibly improve tread wear. Really, all it did was increase the risk of buttress cracking.
Unless stored correctly (read “All About tyres/Storing a tyre” on our http://www.carbonblack.com.au site), the tyres will eventually craze or crack most severely where the tyre is resting on the pipe rack. This is because stretched rubber is attacked by ozone in the air. Ozone is generated by electric motors and lightning, so maybe the shop compressor is the culprit. However, tests done in the past have never been able to show that tyres stored this way will not give a satisfactory life. The deformations caused by the pipe rack run out as soon as the tyre gets run in on the vehicle- say 10 kilometres, depending on the temperature.
The real sleeper in all this is your spare wheel. Stored in the boot, or under the tray of a light truck, it is subjected to high summer temperatures, and may lay there undisturbed for six years or more if you don’t have to use it. Our discussion on what to do about that is contained in “All about tyres/original equipment”. Basically, it has missed out on six years of design improvements whilst sleeping in the car boot, or lying in the dealer’s racks waiting for a sale, or in the South Australian’s case, 14 years.
So should tyres have a “Use by Date?” It would appear that provided they have been stored correctly, there is not a problem with tyres encountered in the usual course of trade. Besides, somewhere out of Broken Hill or Wilcannia or somewhere like that, you will be pleased to find that the tyre service has your badly needed tyre, even if it is a bit dusty.
All that applies to tyres also applies to automotive car batteries of course, for all the same reasons, except that a lead acid battery does in fact have a finite life, and has to be stored correctly with its charge maintained until it is sold. The warranty period then kicks in once it is sold.
Entry filed under: Automotive industry, Choosing the Right Tyre, Environment, Installing & Changing Tyres, Our Experts, Safety, Tyre Industry, Tyre safety & maintenance, Tyre Technology, When to Replace your Tyres. Tags: 20 20, channel 7, life of a tire, life of a tyre, today tonight, tyre use-by-date, tyres.