2. Profile - also known as the "aspect ratio". This affects the height of the sidewall in proportion to the tread width. Lower profile tyres give better high-speed stability and handling, but reduce ground clearance and provide less air cushion.


3. Casing materials - tyre casings are reinforced with synthetic fibres such as nylon and rayon, or steel strands, or a mixture of fibre and steel. The differences in strength and ride comfort are marginal, steel giving longer wear life.

4. Ply rating (load index) - indicates the physical strength of the tyre, in both the tread and sidewall. Higher ratings increase load and pressure limits, and make the casing more resistant to impact damage and punctures, but they also add weight and cost and reduce comfort.

5. Rubber - Most tyres use a similar and standard rubber compound, but specialized variants offer significantly different options (eg silica). Very hard compounds give much longer wear life but less grip, especially on wet tarmac. Very soft compounds give optimum grip in all conditions, but wear rapidly.

6. Tread pattern - there are numerous rib design styles, but broadly each fits into one of three categories: rib patterns for street use, lug patterns for mud and snow, or a medium compromise for mixed on both good and rough roads. Aggressive treads give better grip on loose surfaces, but wear faster and generate more noise.


7. Speed Rating - All good passenger car tyres are designated ("T") for speeds up to at least 190 kph. Vehicles which can attain higher speeds should use "H" rated tyres (up to 210 kph) or "V" rated (up to 240kph) and there are options up to "ZR" for speeds above 300 kph. Adequate rating is essential. High-rated tyres are downgraded once they have been repaired.

8. Tube/Tubeless - tubeless tyres are the more modern technology, with weight and performance advantages (eg cooler running) and quality repair facilities are now generally available.

9. Tyre pressure - generally the manufacturer's exact recommended pressure is best for handling, comfort and even wear. Pressures can be safely and beneficially increased for sustained high speed journeys or rough road use, and/or if the vehicle is heavily laden. Pressures below normal are a safety hazard, reduce handling integrity and make the tyre more prone to punctures, rapid wear, overheating and casing failure.