Why do tyres crack between the tread?

Cracking in tyre tread grooves

Cracking that appears in the grooves between the tread blocks is a common form of tyre ageing.

Why it happens there first

The tread grooves are areas of thinner rubber that are more exposed to the elements. UV light, ozone and temperature changes affect these thinner areas first, causing the rubber to dry out and crack before the rest of the tyre shows visible signs of ageing.

Is it safe to keep driving?

If the cracking is only surface-level and confined to the tread grooves, the tyre may still be safe for a while. However, have it inspected by a professional to confirm. If the cracking is deep, extensive, or has spread to the sidewall, the tyre should be replaced as the structural integrity may be compromised.