Your vehicle’s only contact with the road is the tires. If the tires are not inflated properly, you are in danger.
That’s why you make a habit of checking both tire inflation and the state of your tires. So what happens if you lose the air tire valve cap? Do tires lose air if the tire air valve cap is gone?
Air shouldn’t leave the tire because the tire cap is lost. Air should not leak out of the tire just because it does not have the cap. There are reasons to have the valve cap, but preventing air from steadily leaking out of the tire isn’t one of them.
In this guide, I will look at the purpose of the tire valve cap, what it should feel like when properly pressed on, and give reason for what makes you lose air. Towards the bottom of the article, I will tell you about the different types of valve stem caps as well as how much a replacement is.
What is the Air Tire Valve Cap?
The valve cap doesn’t keep air from leaking out of the tire and whether or not it is on the stem shouldn’t have an effect on whether the air stays in the tire, but it does serve an important purpose that should not be overlooked.
While you are driving, there is snow, water, mud, etc., that may be contaminated with debris and goo. The valve stem cap keeps that from veering into the valve.
For example, if there is too much mud on the valve and you where to remove the valve stem cap, it is likely the valve will be damaged (or at least contaminated) if the mud where to enter the valve. This could also cause your tire to be difficult to inflate should the valve gets too mucky and caked.
Do Tire Valve Caps Fall Off?
Sometimes, a tire valve cap can fall off. If it’s loose, it can lose itself off the tire. This is why we always recommend a secure valve cap.
Sometimes it can fall off from the impact. If you brush the car against the curb, the scraping effect can pop the stem cap off. More damage to the stem is possible which may allow air to leak.
But you want to know what usually happens? It gets lost. This is usually when you take the cap off to fill the tires, and then for some reason you misplace it. When you fill the tires up, always keep the valve caps save to reinstall it back once you have filled the tires.
Are Tire Valve Caps Universal?
Most models have universal valve stem caps. You should be able to step into your local auto parts store and find replacement valve stem caps fit for your tires. In fact, it is difficult to even find valve stem caps sold individually.
If you are driving specialized farm equipment or heavy duty trucks, your valve stem will most likely be different, and you may have to buy your valve caps online or directly from a tire shop.
How Much Should You Tighten Valve Caps?
When you are putting the valve caps back on, you want to just snug them with your fingers—don’t use tools on the valve caps, they shouldn’t be that tight. You could damage them if you overtighten them.
When you are putting the valve cap back on, you will put it on the stem and turn it counter-clockwise until it makes a half turn to make sure the cap has properly seated on the threads. After securing the valve cap just enough so it doesn’t turn anymore, but don’t overtighten it.
Reasons Tires Lose Air
#1. Broken Valve Stem.
A defective valve will cause air to leak, while a valve cap will not. However, the leaking air depends on how bad the valve is broken.
You could have a leak just as small as barely, and on the other hand, it could leak bad enough to hear the air coming out.
#2. Tire Puncture.
If you hit something while driving, it will puncture your tire and let the air out. Common things are screws, nails, and other debris left on the road.
Depending on how the puncture occurs, it could easily plug the hole when it occurs where you would not notice any air leaking out of your tire at first.
Once air leaking starts happening, you could get a patch or a plug put on it. However, there are cases where a puncture cannot be repaired, and you will need a new tire.
#3. Damaged Wheel.
The rim can become damaged when you hit something while driving. Hitting a curb, a pothole, or hitting something on the road can create damage to the wheel itself. If the tire cannot seat correctly on the rim, then air can leak out.
In nearly all cases, damaged vehicle rims cannot be repaired. You will want to get your rim replaced for safe riding on the road.
#4. Broken Bead.
The tire bead is where the seal of the rubber & wheel meet. If the bead isn’t sealed right, air can leak out.
This can happen if a bead is damaged. It can also happen if something gets stuck between the wheel & tire allowing air to escape.
#5. Old Tire.
Tires will age especially if they are not in use. When a tire sits especially in sunlight it can dry rot.
Even if the tire is used, it is still going to degrade overtime. As a tire gets old it will become brittle & the tread will separate allowing air to also leak.
#6. Temperature Changes.
Tire pressure is always recommended to be checked when the temperatures change, as the outdoor temperature has a large effect on the amount of air found in the tire.
The change in temperature will not cause air to escape, however it does change the density of the air pressure.
When the temperature drops, the tires will begin to lose air pressure, and conversely, when the temperature rises, so too does air pressure in tandem. If the temperature drops quickly in a cold spell, it can appear that the tire is losing air pressure.
Over time tires are going to lose some air. The air molecules break down and lose pressure and change its composition which can usually lead to a decrease in psi.
That is why you want to check the tires at a minimum of once a month. By routinely checking your tires, you can catch problems before they impact your on-road safety.
Cost to Replace Missing Tire Valve Cap
You can find a large pack of tire valve caps at a local auto parts store for $10 or less. You may pay more for something for a heavy-duty truck or if you’re looking for something fancy, though.
In general, you don’t need help from others to install valve stem caps. It won’t take you much time. If you need to replace the valve stem in a tire, that is also a straightforward process.
If you can do it yourself, it will cost you about $10 for the valve stem. Otherwise, expect to pay $25 to $50 for the valve stem at your local tire shop.
Different Types of Valve Stem Caps
You will find many types of valve stem caps when you go to the auto parts store or tire shop.
Most people will settle for the cheap plastic caps, which perform great in normal driving situations and will not cause you any problems. You can also buy a big pack to keep on hand just in case.
There are metal dome caps, which are better in hotter temperatures for drag racing or a high-performance car.
There are knurled metal caps, which will make it easier to tighten or loosen the valve caps if the previous metal caps were too tight. Additionally, you can find some with a hex head. On the metal caps, you will notice a special O-ring of some sort or another type of seal that helps keep the valve on tightly.
However, we do not recommend using aluminum or metal tire valve caps instead of the plastic, even if they may look better than your standard cap.
This is because the aluminum or the metal cap can start to corrode or rust causing the valve cap to be next to impossible to remove without damaging the air valve stem.