There's a mass of anecdotal stuff out there, but this is interesting from KwikFit:
Tyres are considered to be ‘new’ and are suitable for retail sale for, up to 5 years from the original date of production with recommended storage guidance from tyre manufacturers.
The industry standard for tyres, based on the German BRV recommendation, is the ‘5 year rule’ for new tyres.
Tyre ageing is commonly identified by small cracks, known as crazing, which appear in the tyre sidewall. This is brought about when UV light oxidises the rubber, causing it to dry out.
While tyres contain anti-oxidising chemicals which significantly slow down the rate of ageing, this wax-like substance is only released when the tyre is in motion. Therefore, if the tyre is not used frequently or is stored away ineffectively, they will age more quickly – rendering them unroadworthy when returned to use. Low mileage, older cars tend to be most at risk from premature ageing – as drivers assume the tyres are still in good condition if they have plenty of tread.
