Tyres
What does it mean to check tyres when cold?
“Cold” means measuring before riding heats the tyres: heat can make the pressure reading higher.
Checking tyres when cold means measuring the pressure before a journey heats the tyre and the air inside it. Use the manufacturer’s figure and a consistent procedure; do not reduce a hot tyre’s pressure to match the cold figure.
Why temperature changes the reading
As you drive, the tyre heats up and the measured pressure rises. That is why the manufacturer’s table refers to cold pressure: comparing it directly with a reading taken after driving for several miles may lead you to inflate the tyre incorrectly.
Automobile Club Parma’s practical guidance treats tyres as cold after the vehicle has been stationary for at least two hours or after a very short journey at low speed. You do not need to guess the temperature by touch: use a stable measuring condition and a pressure gauge. Check the handbook for vehicle-specific instructions.
Measure at the right time
If possible, measure before setting off, after the car has been parked. Check every tyre and compare it with the correct row for your load and tyre size. If you have already driven to a service station, note the reading but wait for the tyres to cool before making a precise adjustment.
Do not deflate a hot tyre to the cold-pressure figure: once it cools, it may be underinflated. If you must adjust it immediately, follow the handbook and check it again cold as soon as possible. If there is rapid pressure loss or damage, do not continue without assistance.
After checking
Tighten the valve caps and keep your gauge clean. If your car has a TPMS, check the handbook to see whether the system needs to be initialised after inflation; procedures vary by model.
A small difference or a warning light that returns may indicate a puncture, faulty valve or another problem. Do not keep topping up without an inspection. A tyre specialist can check for leaks and damage, while the handbook gives the correct pressure; neither check can be replaced by a universal figure.
To revise vehicle checks for your theory test, Quiz Patente Ufficiale offers chapter-based study, exam quizzes and review of mistakes.
Frequently asked questions
How long should the car be stationary?
ACI Parma uses at least two hours parked, or a short journey at low speed, as a guide. Follow any specific instructions in your vehicle handbook.
If I measure a hot tyre, should I let air out?
No. Do not reduce it to the cold-pressure figure. Measure again when the tyre is cold, then adjust it according to the manufacturer’s table.