A tyre in normal use would not last three years. It would have worn out and mostly likely got replaced long before three years is up. Motorcycle tyres just aren't expected, or designed to last that long without deteriorating and hardening.

In the case of your bike, which has been standing, this deterioration will have been accellerated. A tyre sitting in one place with the bike's weight on it, slowly decreasing pressure, resting on cold concrete, atmospheric conditions and the fact it will rarely have got up to temperature in that period will all shorten it's life. Leaving a bike for long periods in one place on a sidestand is particularly bad and will cause one patch of the tyre to deform to one side too.

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