Tyres

Tyres are pneumatic rubber structures mounted on wheel rims that form the vehicle's sole contact point with the road surface. A modern passenger tyre is an engineered composite of rubber compounds, steel belt layers, nylon cap plies, polyester carcass cords, and a steel bead wire — all working together to carry the vehicle's weight, generate grip for braking and cornering, absorb road irregularities, and maintain a consistent contact patch under dynamic loading. The tyre sidewall carries all specification information in a standardised format: for example, 205/55 R16 91V indicates a 205mm tread width, 55% aspect ratio (sidewall height as a percentage of tread width), radial construction, 16-inch rim diameter, 91 load index (615 kg per tyre), and V speed rating (240 km/h maximum). Tyre compound formulation is a balance between wet grip, dry grip, rolling resistance, wear rate, and noise — no single compound excels in all areas simultaneously, which is why premium and budget tyres perform measurably differently despite appearing identical.

Tyres perform four simultaneous functions that no other vehicle component can fulfil. First, they carry the entire static and dynamic weight of the vehicle through the pressurised air column inside — not through the rubber itself, which is why correct inflation pressure is so critical. Second, they generate the friction forces for acceleration, braking, and lateral cornering through the tread compound's molecular adhesion to the road surface — the contact patch (approximately the size of a human hand per tyre) is where every driving force is generated or limited. Third, they absorb road surface irregularities through the compliance of the sidewall and tread, providing the first stage of ride quality isolation before the suspension acts. Fourth, they provide directional stability and steering response by maintaining a predictable slip angle relationship between tyre deflection and lateral force generation. All four functions degrade progressively with wear, ageing, incorrect pressure, and misalignment — making tyre condition the single highest-impact maintenance variable for safety.

Uneven or accelerated wear pattern: Inner or outer shoulder wear indicates wheel alignment error — camber or toe outside specification. Centre wear indicates chronic over-inflation. Both shoulder edges wearing simultaneously indicates chronic under-inflation. A sawtooth or feathering pattern across the tread blocks indicates toe misalignment. Any of these patterns signals a system fault beyond the tyre itself — the alignment, pressure, or suspension must be corrected or the replacement tyre will wear identically.

Vibration felt through the steering wheel or floor at specific speeds: Tyre or wheel balance is off following a road impact, valve stem damage, or after a tyre repair. The vibration speed correlates with the out-of-balance mass — typically 80–120 km/h for passenger vehicles. Wheel balancing resolves this; if vibration persists after balancing, the tyre or rim may have a structural defect.

Bulge or lump visible on the tyre sidewall: Impact damage (pothole, kerb strike) has broken the internal carcass cords, allowing the inner air pressure to push outward through the damaged area. A sidewall bulge is a structural failure — the tyre can fail catastrophically at any moment and must be replaced immediately. Do not drive on a tyres with a sidewall bulge.

Level 1 — Owner check: Inspect all four tyres visually at every fuel stop. Look for visible damage (cuts, bulges, embedded objects), check that tread wear indicators (small rubber bars across the tread grooves) are not flush with the tread surface, and check that inflation appears correct. A tyre that looks noticeably lower than the others requires pressure measurement before driving. Inspect tyre sidewalls for cracking, which indicates UV and ozone degradation in tyres over 5–6 years old regardless of tread depth.

Level 2 — Detection: Check tyre pressure with a calibrated gauge monthly and before every long journey — always when the tyre is cold (vehicle stationary for at least 3 hours). Reference the vehicle's tyre placard (inside the driver's door sill or fuel filler flap) for the correct cold inflation pressure, not the maximum pressure printed on the tyre sidewall. Increase the pressure by 0.2–0.3 bar above the placard value for fully loaded or motorway driving. Measure tread depth with a depth gauge at the central rib and both outer channels — replace at 3mm for safety, legal minimum is 1.6mm.

Level 3 — Professional service: Have wheel alignment checked every 20,000 km or after any significant kerb or pothole impact. Alignment errors produce tyre wear patterns that confirm the specific fault to a technician. Replace tyres in axle pairs at minimum — mixing significantly different tread depths on the same axle creates unpredictable handling during emergency manoeuvres. On rear-wheel-drive vehicles, fit the better-condition tyres to the rear axle.