Should tyre pressures be checked when tyres are hot or cold?

Cold. Northern Ireland's road-safety guidance recommends checking pressures before a journey, when the tyres are cold.

Warm tyres can produce a misleading reading. Use the manufacturer's pressure for the load and check regularly, especially before carrying passengers, luggage or towing. Uneven wear may indicate incorrect inflation or wheel alignment and deserves investigation rather than simply topping up the tyre.