Tread wear isn't the sole reason you should replace your car's tyres

[caption id="attachment_2052" align="alignnone" width="600"] Collector cars often need tyre replacement before the tyre tread wears-off[/caption]

Generally, people know that it is time for replacing tyres when the tread is worn-out. This is alright for people who use their vehicle frequently. However, there are few people who drive their vehicles occasionally (or even rarely) and tyre treads remain usable even after 5-6 years. These are the kind of people who need to reconsider their method of checking tyre wear as their car's tyres possibly age out before wearing out.

Tyres are composed of components like steel belts, rubber compound and fabric plies. The structural integrity of tyres can degrade overtime due to cyclic fatigue, chemical reaction within the rubber components, chemical reaction after using hazardous chemicals and other internal structure damage.

[caption id="attachment_785" align="alignnone" width="600"] Internal structure of a radial tyre[/caption]

That said, there is no specific way of knowing how long the tyres will last due to the variables involved. Exposure to the sun and hot climates determines the tyres' degradation level. Vehicles that are parked in indoor garages and driven daily in moderate climatic conditions potentially have the longest lifespan.

Basic tyre maintenance also plays a vital role to prevent tyre aging. This include things like regular cleaning, checking air pressure, periodic tyre rotation and wheel alignment. Another variable for tyre aging is how the tyres are used. Under-inflation/Over-inflation and use on roads with potholes/curbs can weaken their internal structure.

However, even if the tyres are used in good environment and are care for properly, the factor of calender age still exists. Usually, a tyre manufacturer's warranty is valid for 4-6 years. Most of the times, tyres reach the end-user after 6-12 months from the date of manufacturing. Therefore, one should also take this into consideration.

[caption id="attachment_2055" align="alignnone" width="607"] Tyre speed rating chart[/caption]

The US National Highway Traffic Safety Administration (NHTSA) indicated that there is a strong correlation between speed rating of a tyre and its durability. Tyres with higher speed rating degrade least with increasing calendar age. Therefore, if a vehicle is driven in hot climate mostly, then going for tyres with higher speed rating than the OEM tyres can reduce the aging due to time.