A tyre can look perfectly normal yet be soft enough to change how the car stops. The common mistake is waiting for visible sag or a dashboard warning before checking, allowing gradual underinflation to weaken braking response, particularly on wet autumn roads.
Why low pressure hides
Modern tyres often have stiff sidewalls, so pressure loss can be difficult to judge by eye. A tyre may already be affecting the car before it looks obviously low. Underinflation allows excessive flex, making steering less precise and the tread less stable when the driver brakes hard.
There is no fixed number of metres added by low pressure. Speed, road surface, tyre condition and vehicle load all influence the result. Even so, a small loss across several tyres can lengthen an emergency stop while also increasing heat build-up and uneven wear. The absence of an obvious handling problem does not prove that the pressures are correct.
Checking pressures cold
Check pressures at least monthly, before longer journeys and after a noticeable temperature drop. Measure with the tyres cold and follow the vehicle manufacturer’s figures, usually found inside a door opening or in the handbook. Do not use the maximum printed on the tyre sidewall as the normal setting; it is not the car’s recommended cold pressure.
- Measure all four tyres with a reliable gauge, not only the tyre that looks soft.
- Compare each reading with the recommended cold pressure and correct it as needed.
- Use the higher listed setting for passengers or luggage if the manufacturer specifies one.
- Look for nails, cuts, cracked rubber or one tyre losing pressure faster than the others.
A tyre pressure monitoring system can warn of pressure loss through the dashboard. It remains a warning device rather than a substitute for a gauge: it may not flag smaller losses or a similar reduction across more than one tyre. Regular manual checks therefore still matter.
When air will not hold
If one tyre repeatedly needs air, do not keep topping it up indefinitely. A nail, leaking valve, damaged wheel rim or poor seal between tyre and wheel may be responsible. Vibration, pulling under braking or unusual shoulder wear also warrants professional inspection. A workshop check may take roughly 15–30 minutes; a repairable puncture often costs tens of pounds, while sidewall damage usually means replacing the tyre.
Check the pressures cold this week, then recheck after a few days if any tyre was significantly low. If it falls again, treat that as a fault to investigate, not an inconvenience to keep refilling.