Will Tire Go Flat Without Cap? [Explained!]

It is can be frustrating sometimes when you go to check the tire pressure and find the valve caps missing. The worst is when the tire is low on pressure.

This is because you might think that it is the missing cap that could have led to a flat tire. However, how true is this? What happens to tires if the air cover is gone? Will tire go flat without a cap?

Yes, you can still drive your car without tire caps. Air won’t be able to seep out of the tire just because it’s missing a cap.

You should know that the tire valve caps serve many other users, but none of them is related to keeping the air in the tire.

The main function of the caps is to keep dirt and debris from getting stuck in the valve stem so that the next time you come to fill the tire with air, it is easier to do so.

Functions of Valve Caps

types of valve caps

Valve caps can do many things for your tires and valve stems. We will look at the different types of valve caps to understand how best they work and what are their functions. The two main types of valve caps include;

  • Schrader caps

The Schrader caps are the most common types you can find on tires. This includes bikes and car tires. They are characterized by having a cylinder shape for housing the valve.

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Their main job is to keep the dirt and contaminants from penetrating the valve seal.

The cap is also important to protect the valve’s interior parts from road debris and rocks. Too much exposure to the elements would damage the valve stem interior parts.

Here is a video of how a Schrader valve works

YouTube video
  • Presta caps

Presta valve caps do not have the most use as compared to the Schrader caps. Their job is to protect the thinner tubes while being shipped.

That is the only time these caps are useful. Once the tube is installed on the bike, it might not have as much use as the other type of caps.

Another potential reason people use valve caps is that they want aesthetics. These caps are supposed to be simple and functional.

However, since there are many companies making the same product, each brand wants to stand out. That is why they will make them in different shapes and colors.

Can the Valve Caps Fall off?

It is possible that the valve caps will fall off because you had not tightened them properly.

Most of the time, people would have an attendant put air pressure into their tires without getting out of the car.

So, some of the attendants do not screw the caps back onto the tires correctly and thus you end up with valve caps that fall off easily.

Also, sometimes you might bump the tires against the curbs. There is a risk of rubbing the valve stem against concrete.

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Depending on the impact, it is possible to snap off the valve cap. Considering most are plastic, they can come right off.

Another way you can lose valve caps is when someone steals them without your knowledge.

For some reason, there are those who steal valve caps. Maybe you have metallic caps or they have a nice design and someone thinks they should belong to them.

Because it seems sometimes you may lose your valve cap, someone might ask how tight it should avoid this from happening.

For the most part, valve caps should only be finger-tight. You should not need a tool to start loosening the caps when it is time to put more air pressure into the tires.

Also, tightening it too tightly can risk damaging the valve stem itself.

Align the cap with the stem and turn it clockwise to get it into the valve stem threads. You should not have a hard time tightening the valve cap.

Reasons You Are Losing Tire Pressure

Tire Go Flat

Now that we have established the missing valve caps have nothing to do with losing air pressure, what could be the reason then? Below are some of the reasons you keep losing tire pressure.

1. Corroded wheel beads

The wheel beads are important for ensuring there is a good seal between the wheel and the tire. However, when the beads are corroded, then the seal would not be so good and now you keep losing tire pressure.

Tires such as magnesium or aluminum alloy tend to be prone to corrosion and rust. One thing about these types of leaks is that they are slow and can take a while to detect that you are losing air pressure around the rim.

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You can check if the tire is leaking around the rim by spraying soapy water around the rim and watching out for any bubbles. In case there are bubbles, it is then important to have the tire resealed to avoid this from happening again.  

2. Puncture

This might be the most common way of losing tire pressure. A tire puncture can happen due to many things. Sometimes you might hear it while other times you may not because it is a slow puncture.

The loud puncture can often be scary. However, if you have a spare tire, it should not be hard to get it sorted as you drive around with the spare tire.

The only way you would notice it is a slow puncture is how often you have to keep adding air pressure to the tire.

If you can notice that it is necessary to keep adding the air pressure, it is then best to consider having it checked and having the puncture plugged.

Modern cars now come with an air compressor and a tire repair kit. This means that you can actually repair the tire on your own. The car manufacturers do this because they do not include a spare tire in the car.

Here is a video on how to repair the tire with the repair kit

YouTube video

3. Bent rim

When you have a tendency of hitting potholes or curbs, the chances are you would end up with bent rims. Sometimes the bend can be so serious that you can actually see why you are losing tire pressure.

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How about the small bends in the rim? The bend might not be so big to a point you might not think it would be leaking air.

Have the tire checked by a professional to see if there is a problem with your rim and have it repaired.

As for repairs, not all bent rims can be repaired. This is because sometimes the damage is too much to be repaired. In such a case, just have the wheel replaced.

4. Old and worn tires

What most people do not know is that tires can also expire. You might get some people using the same tires for years without replacing them.

Make sure you look at the tire sidewall to find out more information about when the tire would expire.

When the tire is too old, it tends to have dry rotting. The dry rot would make the tire start having cracks. When this happens, then you will start losing air pressure easily.

The solution to this problem is simply to buy new tires and replace the old ones.

5. Damaged valve stem

You may also be losing air around the valve stem. When the valve stem is damaged, it is possible to start losing some tire pressure.

Valve stems are not expensive. They are only a few bucks so have checked after a few thousand miles to avoid losing tire pressure.


What is the job of valve caps?

The valve caps are important for keeping dirt and other road debris from getting into the valve stem.

Will losing the valve caps lead to a loss in tire pressure?

No. The valve stem has a proper seal that would still keep working even if you lost the valve caps. Just make sure you have the valve caps to avoid dealing with debris in the valve stem.

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What is the right air pressure?

That will vary a lot depending on the car. However, the standard passenger cars would have a range of 30 to 35PSI. Check the owner’s manual of your car to see what the manufacturer recommends.

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