I have lots of questions about the air pressure in my tires.
What is the perfect tire air pressure?
Do I fill my tires when they are hot or cold?
Winter/Summer tire air pressure?
Will lowering the tire air pressure help when driving on snow?
What is low tire pressure, and does it really matter that much?
How much is my fuel economy affected by low tire pressure?
What if I just overfill my tires?
What is the perfect tire pressure?
The manufacturer has a desired tire pressure for your car as delivered.
The manual will tell you the pressure. You may have a sticker on the door sill or a sticker on the gas flap that will tell you the pressure.
The pressure marking on the actual tire is not the running pressure, but the max pressure or storage pressure. Do not use this as a guide, stick with your manual or tire sticker chart.
Do I fill my tires when they are hot or cold?
I have my perfect tire pressure, now do I fill my tires when they are cold to this pressure, hot, or somewhere in between.
Tire manufacturers suggest checking tires when they are cold for the most accurate reading. Outside temperatures can cause tire pressure to vary by as much as 1 psi per 10 degrees; higher temperatures mean higher psi readings.
Air expands as it heats up, and contracts when cold.
When the tire is heated, the air molecules inside start moving faster. These molecules now collide into the tire with more energy resulting in increased pressure. The increased pressure causes the tire to expand.
There is still the same amount of air molecules, just spread out more, in other words, hot air is less dense than cold air. If it is necessary to adjust inflation pressure when tires are “hot”, set their pressure to 4 psi (14 kPa) above the recommended cold inflation pressure.
Most manufactures recommend between 28 and 45 psi, don’t worry burst pressure is about 200psi! It is better to be slightly over than underinflated. Most passenger cars are good at 32psi.
Winter/Summer tire air pressure?
With summer temperatures expanding the air all the time you can set slightly higher pressure when “cold”. In winter the reverse is true, the air is always a little denser so you can set slightly lower than recommended cold setting.
If you have a car that reads the tire pressure while you are driving, you are going to see higher pressures while driving. If it is going over your recommended pressure by more than 4-5 psi, I would check again the next morning when the tires are cold and reset to factory specification.
Will low tire air pressure help when driving on snow?
I had heard that when you want to drive on sand you would do better with low tire pressure?
Is snow the same as sand when it comes to tire air pressure?
Snow is not sand, whatever pressure you normally run on the street in warm weather is the place to start. If you are coming from a warmer environment to the snow you could even add 2 PSI. Because snow will keep tire temps lower than a typical cold but dry day. Snow sucks heat out of tires faster than air will by conductive cooling.
Whatever you do, ignore any advice to air down. Snow is not like sand; you do not want additional flotation.
The best way to drive in snow is to have a purpose-built tire for winter driving. Next best is to use chains and for an emergency a fabric snow sock. Living with snow 4 months out of a year is quite different than just visiting the snow for a day!
What is low tire pressure, and does it really matter that much?
Most tire manufactures recommend between 28 and 45 Psi. A tire is considered flat when under 20 psi.
Most tire-pressure monitoring systems warn you when your tire air pressure drops by about 10 percent. Anything more than three or four pounds below normal can cause handling problems and increases the potential for a blow-out. Low tire pressure always is more dangerous than high tire pressure.
If the tire air pressure is too low, it can cause unsafe driving conditions. Low tire pressure can also cause the tires to wear prematurely, and lead to tire failure. Driving too long on underinflated tires can cause the tires undue wear, reduce gas mileage, and present safety hazards.
How much is my fuel economy affected by low tire pressure?
For every 1-psi drop in pressure, you can expect your gas mileage to lower by 0.4 percent.
What if I over inflate by 1ps, will this raise my fuel economy?
No, overinflating your tires will not have the same gains as you lose by underinflating.
It is great to have better fuel economy, but a lot of wear damage happens to the tire when it is underinflated. Buying new tires prematurely is way more of an expense than your fuel savings. Wear on tires if just 5 psi below advised, pressure could lessen a tire’s tread life by as much as 25%.
Low tire air pressure directly affects ride control and braking. Under-inflation is one of the leading causes of tire failure. If tire pressure is too low, too much of the tire’s surface area touches the road, which increases friction. Increased friction can cause the tires to overheat, which can lead to premature wear, tread separation, and blowouts.
What if I just overfill my tires?
Over inflating your tires by a little bit will not hurt, one to two psi, the temperature swing can affect the pressure of the tire by as much as 8 psi. But overinflating your tires is as bad as under inflating.
When overinflated, your tires round out on the center tread section, causing the center to wear significantly faster than the outer edges. Your tires might only last half the life they normally would. Overinflation can cause loss of traction when there is less tread surface area on the road.
Conclusions on Tire Air Pressure
A typical tire may lose 1 to 2 psi a month if not checked and adjusted, so keeping up on your tire pressure is worth it. Setting the recommended tire air pressure is best.
When filling the tire you can overfill and release the pressure to the correct psi. The fill gauge can be a little rough to read, so using a tire pressure gauge is best. You can check your car if it has a digital read out for each tire.
Don’t lose your air caps! That little cap can prevent water from entering the valve and freezing. The freezing could expand and push on the valve, losing air could result.
I’m going to check my air pressure right now, while my tires are cold!
