Tyre Cracking

Tyre cracking (weather checking) is a classic sign of rubber ageing. Unlike sudden structural damage like tyre bulges, cracking typically develops gradually over time.

Causes of Tyre Cracking

Physical oxidation (rubber ageing): Rubber compounds contain anti-ageing chemicals and antioxidants that deplete over time. Prolonged exposure to ultraviolet (UV) rays from sunlight, ozone, and severe temperature fluctuations causes the molecular chains to break down, resulting in fine hairline cracks on the surface.

Loss of physical properties: The appearance of cracks indicates that the rubber compound has hardened, turned brittle, and lost its elasticity. This directly reduces tyre grip, particularly in wet conditions or during emergency braking.

Prolonged parking / incorrect tyre pressures: When a vehicle is left stationary for extended periods, constant pressure on the contact patch accelerates rubber ageing in the deformed zone. Similarly, driving on incorrect tyre pressures causes uneven internal stress distribution across the rubber, inducing crack formation.

Risk Assessment: When Must Tyres Be Replaced?

How you should deal with tyre cracks depends largely on their depth and location:

Minor surface cracks (hairline/crazing cracks): If the cracks are superficial, confined strictly to the sidewall surface, and do not reach the underlying carcass, this is generally considered normal ageing. As long as the tread depth remains within legal limits, the tyres are still usable, provided you check tyre pressures and inspect them visually more frequently.

Deep cracks (exposed cord/ply layer): If cracks are deep enough to expose the internal cord ply, fabric belts, or steel wires, the tyre must be replaced immediately. This indicates compromised structural integrity and poses a severe hazard. 

Shoulder/bead cracks: Cracks appearing along the tyre shoulder (the area subjected to the highest flex and stress) indicate that its structural resistance to deformation is severely weakened. Replacing the tyre as soon as possible is highly recommended.

Prevention and Maintenance

Parking environment: If your car is left unused for long stretches, try parking it in a covered garage. If open-air parking is unavoidable, tyre covers can effectively shield the rubber from UV rays and ozone degradation. 

Avoid corrosive contaminants: Keep tyres away from oil spills, harsh acidic substances, and caustic chemicals, as these will rapidly break down and degrade rubber compounds.

Realistic expectations for tyre dressing / wax: Aftermarket tyre dressings and waxes can provide a temporary UV-protective barrier. However, once cracking has set in, dressings merely enhance appearance and cannot restore lost rubber elasticity or strength. 

Regular inspection routine: For tyres older than 3 years, conduct a thorough inspection for cracks at least once every six months.