You may or may not know; tyres are marked with their date of manufacture on its sidewall (See picture). It is coded as week and year of manufacture, example 0109 would mean the tyre was manufactured in Week 01 of Year 2009, and similarly 0111 would mean week 1 of 2011.
Shelf life of tyres
Naturally, the next question would be the shelf life of tyres. Most major manufacturers give their brand of tyres 4 to 5 years shelf life- meaning a tyre is considered “fresh” to be fitted onto a car as long as done within this 4 to 5 years from date of manufacture. And the tyres fitted will usually be granted a “limited tyre warranty”. This limited warranty is also usually up to a tyre’s useful tyre life- in many instances up to a remaining tread depth of 1.6mm. This may in some countries be regulated to be more than 1.6mm remaining thread depth.
Finland brand “Nokian” for example gives limited warranty for three (3) years from date of purchase or five (5) years from the manufacture of a tyre, whichever is earliest. In Nokian’s case, this limited warranty applies where the tread depth of a tyre meets the requirements of the vehicular laws of the country where the tyre was sold. Manufacturers usually cease warranty beyond 1.6mm remaining tread depth (for passenger car tyres). It is therefore safe to assume that tyres must not be worn beyond this marker.
It is a limited warranty because once a tyre is fitted, there are many reasons beyond or totally unrelated to “manufacturing related” defects. Manufacturers will not be liable for a warranty of a tyre should any of the following occur:
a. Tyres are damaged by road hazards, fire, accidents, corrosion, or other acts of God
b. Tyres are of normal wear and tear
c. Tyres were misuse for example via kerbing, running over foreign objects and potholes.
d. Tyres damaged from improper fitting, improper inflation pressure, faulty rims, negligence, alteration or repairs
e. Use in motor racing or exceptional use
f. Tyre noise from uneven wear
Compensation of tyres
It is understood that the “failure” of tyres due to manufacturing defects, particularly for major brands are extremely low- 1 in 10,000 tyres perhaps, and usually these “failures” are of very negligible consequences. But should compensation of tyres be allowed, it is always limited to the “unrealized benefit” from the tyre in use- this simply means compensation are pro-rated or calculated based on unused thread depth of up to 1.6mm. Most passenger car tyres are of 7mm to 8mm thread depth when new.
How old is too old?
A tyre left in the sun for a year is going to be very different in character as compared to one stored in an indoor condition. It is however not easy to change the characteristic of a tyre once it is manufactured. For a fact, most passenger car tyres are cured at a temperature in the region of 130-140 Degree Celsius for about 30 minutes to form its permanent elastic character- and it is safe to assume that it may take something equivalent or close to change its character further.
Given that most motorists cover an average of 25,000km a year, and tyres these days are usually worn out at about 50,000km- it is therefore safe to say that a tyre being up to 3 years old will be considered safe to be installed- assuming the manufacture gives a 5 years’ warranty.
Should dates of manufacture be the same for all tyres changed?
It may be unnecessary for tyres to be exactly the same manufacturing date since some common tyre sizes are manufactured almost 365 days a year- which means to say that the same tyre may come from the same manufacturing line, from the same factory and potentially be a few months apart when warehoused and delivered to its consumers.
All things said, the manufactured date of a tyre may be important, but nothing beats regular inspection, proper tyre inflation pressure and most of all- safe driving habits!