Read the specified fitment
Use the handbook, vehicle placard and advice for the exact vehicle to establish the specified tyres. The markings on an existing tyre describe what is fitted; they do not prove that the fitment is correct. Note front and rear differences, and leave substitution decisions to a competent tyre professional.
Keep pressure separate
Recommended pressures depend on the vehicle and load. Find the manufacturer’s figures and instructions, including whether the reading is to be taken cold. The maximum pressure printed on a tyre sidewall is not a universal recommendation for your car.
Observe without diagnosing
From a safe parked position, note obvious damage, bulges, cracks or something that has changed. A tread gauge can help record a measurement, but a number alone does not establish roadworthiness. Uncertain damage, continuing pressure loss or an unusual feel needs a professional assessment.
Make the record useful
Write down the date, tyre position, stated size and the source of the correct pressure information. If you buy a gauge or inflator, compare its range, connections, accuracy information and instructions. Having the right tool is useful only when the reading is compared with the right specification.
Sources & further reading
Source links reviewed 9 October 2026. UK guidance is labelled; check Manx requirements separately.