why the pressure of the air in cars should be checked only after the car has been driven for some distance?

Question

manufactures recommend a specific pressure for cars to ensure best performances, why?

Answer 1

When your car is moving the tires are "flexing" and that causes heat which causes the air inside them to expand.

To insure you do not over-inflate your tires fill them after driving.

8-)

Answer 2

You have it backwards. The air pressure in tires should be checked when the tires are cold. The tires will only be cold if you have not driven on them. In general, check the air pressure in your tires before you've driven more than a mile (1.5 km).

Tire pressure is very important because it affects the braking, handling and gas mileage of a car. If the pressure is too low, the car's handling will become sloppy and the gas mileage will suffer. If the tire pressure is too high, the car will ride stiffly and the tires will wear out quickly. Always follow the car manufacturer's recommendations for tire pressure.

Answer 3

Actually, I've always heard the opposite -- that tire pressure should be checked and adjusted when the tires are rested (air temperature.) When the car is driven for any length of time, the air in the tire heats up causing expansion (greater pressure.)

Maybe because my cars are older I still have the "old" way of checking the pressure?

Answer 4

Air pressure in tires should be checked when cold, as hot air expands and gives a false reading. Manufacture specs are given for tire pressure to keep heat build up down, and to make sure tire will support the weight of vehicle.

Answer 5

Manufacturers specify the cold (not hot) temperature because it's easy to measure accurately and consistently. Otherwise, you would need to measure the temperature of each tire, make sure that temperature is uniform and has been steady long enough to heat the air to that temperature, and then compare your pressure reading of a chart of suitable pressure as a function of temperature. We assume you are asking about tire pressure.

The pressure specified is just one component of a complete tire design. It should provide safe operation over the entire range of conditions you are likely to experience while driving. A design using higher pressure would generally have lower temperature, lower rolling resistance, longer tire life, but a rougher ride and a higher risk of damage from bumps.

If you use a pressure that's not the one for which the tire was designed, you won't get the designed performance, you risk damage, and you void the warranty.

Answer 6

Because the tires warm up while you drive. This higher temp makes the pressure go up. If the tires are cold, you will get a low pressure reading and over inflate the tires.
Your tires are designed to operate at a certain pressure. Over inflating makes for a smaller contact patch (how much tire is on the road). Under inflating makes the side walls of the tire wear out faster. More importantly, decreases handling, an un-safe condition.

Answer 7

air pressure increases as the tires (and air inside them) heat up from driving. what was 32 psi may become higher. i don't recall whether you check pressure warm or cold.

over and under inflation causes un even tire wear and in extreme situations can cause premature tire failure, un safe handling etc.

try filling your tires to seventy pounds and see if the ride becomes quite unstable. it will be like driving on super balls.
(ps don't really try this.)
under inflated tires are squishy and greatly reduce the handling of the car.

read the tires and don't exceed recommendations of the manufacturer

Answer 8

Tire pressure should be check with tires cold (except in the dead of winter). As the tires heat up, the air expands, giving you a false reading.

Answer 9

Because as tires are driven on they get hotter which equals more air pressure.

Answer 10

Heat generated by driving expands the molecules and causes a rise in pressure. If you want to avoid this you can replace the air in your tires with nitrogen which has stable molecules.....