Tires are one of those items that sometimes easily can get forgotten about when ensuring our vehicles are in tip top shape for that next big trip, or commute to work.
Let’s learn more about one of the most simple maintenance items that every vehicle owner should know how to do. Checking their vehicles tire pressure.
Why do tires lose air pressure?
Tires lose pressure for many reasons; it is actually normal for a tire to lose air pressure over tire.
The air in a tire has very small molecules, these molecules over time can “leak” out of the molecular structure of the rubber in the tire. This process of the molecules being released through the rubber of the tire is known as Permeation.
Permeation results in a pressure decrease but it is not very large, it can be accounted for roughly 1 psi per month. So, you can imagine that it would take a period of many months to cause your tire to deflate only due to permeation.
The other cause of a tire to lose pressure, and the one that we notice as vehicle owners is a “leak” in the tire.
Normally these leaks are caused by a nail in the tire, a damaged valve stem or a bead leak. A bead leak is caused by excessive corrosion building up between the rim and the bead of the tire. This corrosion allows are past the bead and as a result leaks out of the tire.
Do I need to check my tire pressures?
Yes, you need to check your tire pressure often. Underinflated tires are not only a safety concern but tires that are not correctly inflated can also lead to many other issues with your vehicle.
Tires that are not inflated to the correct pressure can cause excessive tire wear. Depending on if the tire is over or underinflated the tire wear will change.
When the tire is underinflated, the outside edges will contact the road surface with the most pressure causing premature tire wear.
However, if the tire pressures are above manufacturers specifications, or overinflated. You will notice the center of the tire wearing prematurely. This is caused by the tire partially ballooning causing only the center portion of the tread to contact the road surface which leads to the wear in the center portion of the tire.
An underinflated tire can cause many other issues, one of them that will drastically affect your pocketbook. An underinflated tire will cause multiple handling issues as well as a decrease in fuel economy.
The U.S Department of Energy has stated that when tires are inflated correctly it can increase your fuel economy by up to 3%. Because of the increase in fuel economy your vehicle will also produce less emissions as it is burning less fuel.
The fuel economy increase is good news, with today’s fuel prices I think we could all use an increase in fuel economy, even a small increase.
Do I need to check pressures if my vehicle is equipped with tire pressure monitors?
Yes, you still need to check your tire pressures even if your vehicle is equipped with tire pressure monitoring technology.
Tire pressure monitors have a threshold that needs to be passed before the low tire light will illuminate. This ensures that the low tire light does not turn on and off multiple times during a day of driving.
This threshold may be 5 psi lower than the manufacturers recommendations. For example, if the manufacturer recommends a tire pressure of 40 psi, the low tire light will not illuminate until the tire has dropped to 35 psi or below.
So, a tire that is low in pressure and has not caused the low tire light to illuminate can lead to the affects that we discussed above. Increased tire wear, increased fuel consumption, and poor handling.
Also ensuring that you check your tire pressures manually can allow you to notice if you have a problem with your tire pressure monitor system. If the light is illuminated and you checked and set all of your tire pressures than a trip to your local garage is needed.
This is why it is always important to still check your tire pressures even if your vehicle is equipped with tire pressure monitors.
How often should I check my tire pressures?
You should check your tire pressure at least once per month. As a good part of routine maintenance, you could combine this check with other items as well.
I would recommend that when you are checking your tire pressures once per month you take a good look at the tread and overall condition of your tires at the same time.
This will give you a chance to have a good luck at the current condition of your tires and ensure that you are alerted if you see abnormal tire wear or other items that may turn into a safety issue in the near future.
How do I check my tire pressures?
Checking your tire pressure is one of the simplest routine car maintenance items that all vehicle owners can accomplish on their own with only a few simple tools.
However, there are a few things that you need to be aware of to ensure that it is done correctly.
First you need to know what the correct tire pressure is for the vehicle that you own. This can be found on the Tire and Loading information tag, this tag is generally located on the d/s door jamb. Among other items about seating capacity this tag shows the correct cold tire inflation pressures for the front and rear axle of the vehicle. The tag looks very similar to the image below.
If this tag cannot be found, you can also find the manufacturers recommended tire pressure in the owner’s manual for the vehicle.
There is also a maximum inflation pressure on the sidewall of the tire. This is not what we are going to set the tire pressure too. This pressure is the maximum pressure that the tire is capable of holding, not the manufacturer of the vehicles recommended pressure.
If you noticed when checking the tag on the door jamb, it mentions the Cold Tire Inflation Pressures. The reason that you want to check your tire pressures when they are cold is as a tire is driven down the road the friction between the road surface and the tire creates heat.
Because of some interesting gas law that was discovered in the 17 or 1800’s, but we do not need to get into that discussion. The heat that is generated from the friction causes the pressure inside of the tire to increase.
So, by ensuring that we set the tire pressures at their cold recommended pressures we ensure that the tires are filled correctly as per manufacturers recommendations.
Use a Proper Gauge when checking your tire pressures
Most vehicle owners do not have an air compressor in their homes so you will find that you end up using a local gas station to fill up and check your tire pressures.
Some gas stations will have a pressure gauge attached to their air nozzle that you can use to check your pressures as well. I would highly recommend that you do not use this gauge to check your pressures.
As you can imagine, this community air filling station will see many people using these gauges through out the day. Not everyone knows how to treat these tools properly which can result in damaged tools that do not read accurately.
I would recommend purchasing your own “pencil type” pressure gauge from an online source or local reputable parts supplier.
These items do not generally cost much, and you can place them in the glovebox of your vehicle, so you know where they are when you need to access them.
By using your own pressure gauge, you can ensure that the gauge will read accurately when checking your pressures. This will also allow you to check your pressures at home and if the tires are within specifications, you will not need to make that extra trip to the gas station.
I hope this clears up some of the common questions that you may have regarding checking your tire pressures. If you have any other questions, drop them in the comments.