Tyres, Wheels and Pressure
Reading a tyre, why pressure matters and what causes uneven wear.
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What you will learn
- Decode a tyre size
- Explain pressure effects
- Recognise wear patterns
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A tyre sidewall carries the size (for example 205/55 R16), the load and speed ratings, and the DOT date. The size tells you section width, aspect ratio and rim diameter; fitting a different size changes the speedometer and gearing.
Correct pressure matters more than many drivers think: too low causes overheating and edge wear, too high causes centre wear and less grip. Uneven or feathered wear points to alignment or worn suspension, not just pressure.
| Wear pattern | Likely cause |
|---|---|
| Both edges worn | Under-inflation |
| Centre worn | Over-inflation |
| One edge worn | Camber / alignment |
| Feathered | Toe / worn suspension |
| Flat spots | Braking lock-up / balance |
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Key points
- Read the sidewall before replacing a tyre.
- Pressure is checked cold and to the vehicle spec.
- Wear patterns diagnose alignment and suspension faults.
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Key points
- Tyre size encodes width, aspect and rim diameter
- Pressure affects grip, wear and economy
- Wear patterns point to alignment or pressure faults
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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