Bike Tire Deflates When Removing Pump: Why Does This Happen?

Nobody wants their journey to get hampered by a flat tire when cycling. A good practice is to always check tire pressure before going for a ride. That includes pumping it up. But when doing so, sometimes, the bike tire deflates when removing the pump. Why does this happen?

There can be several reasons behind this issue, including but not limited to incorrect valve type, poorly seated valve, worn valve or valve stem, faulty pump, or an overinflated tire. Each issue is covered in detail below.

A little bit of air loss after removing the pump is standard. You will usually hear a small whiff when you detach the pump, but this is from the compressed air in the pump and not the tire.

However, a damaged valve can cause deflation after disconnecting the pump. Let’s find out more about the nature of bicycle tire valves to understand why this is a problem.

The Bike Tire Valve

The valve is the tiny mechanism that lets you pump air into or let the air out of the bike tire. It protrudes directly from the tire’s inner tube, where you can connect your bike pump to pump air into it. The two most common types of bike tire valves are the Presta and Schrader valves.

The Schrader valve looks a lot like the valve you would find on a car. It is wide and has a flat top. The Presta valve, on the other hand, is slender with a locking nut at its end that can be loosened to let the air out of the tube.

The Schrader valves are more popular because they are cheaper to produce, and that’s why they are found on most standard bikes.

There is also a less popular third valve type – the Woods (Dunlop) valve. This valve looks like the Schrader valve but is wider in width. It is popular in bikes in Europe, Asia, and many developing countries. It is most commonly used on city bikes in those regions.

How do Bike Tire Valves Work?

Schrader Valve

The Schrader valve works with a spring-loaded check valve. When pushed down, the valve lets air flow through a pump. Thanks to the spring, the center pin pops back into place when released. This locks the valve and prevents airflow.

Presta Valve

This valve is the most complicated. The Presta valve requires you to unscrew its metal cap. When it gets to the top, pressing it will let the air out. This way, you can attach a pump or let the air out. When you’re done, all you have to do is screw the cap back to lock the valve.

Woods (Dunlop) Valve

Attaching a pump directly to the Woods valve lets you pump air in. However, to deflate it, you must remove the valve core. First, remove the rubber cap if you have one. Then, remove the top nut. After that, pull the valve core from the valve stem. Hold on to the valve core tightly because the air will start rushing out of the tube after removing it.

Main reasons why bike tires may deflate after the bike pump is removed

There can be several reasons behind this issue, including but not limited to incorrect valve type, poorly seated valve, worn valve or valve stem, faulty pump, or an overinflated tire, let’s look at each in little more detail:

  1. Incorrect valve type: We covered three types of valves above; if you use the wrong type of pump for your valve, the pump may not correctly seal the valve, leading to air escaping when you remove the pump or even while you inflate the tire. So ensure you get the right pump for your bike’s valve type.
  2. Poorly seated valve: If the valve is not properly seated in the valve stem, air can escape when you remove the pump. so make sure the pump head is correctly seated on the valve stem.
  3. Worn valve or valve stem: If the valve or valve stem is worn, it may not form a tight seal with the pump, allowing air to escape when you remove it. Causing the tire to lose air.
  4. Faulty pump: If your pump is faulty, it may not be able to maintain pressure in the tire.
  5. Overinflated tire: If your tire is overinflated, air can escape when you remove the pump, as the pressure is too high for the valve to handle.

To summarize, make sure you are using the correct pump for your valve, check that the valve is properly seated, and make sure your pump is in good condition. Additionally, be mindful of the pressure in your tire and avoid overinflating it.

How Did My Bike tire Valve Get Damaged?

In most cases, a damaged valve isn’t your fault. These are tiny mechanisms with moving parts, and wear and tear can happen. As you keep using the valve, the parts will eventually deteriorate. You’ll have to replace the valve when it fails so you can keep pumping your tires properly. 

The valve can also be damaged if it gets struck with debris while riding. Always check your valves for bends or any other signs of damage. Sometimes, dirt can get stuck in the valve and cause it not to close correctly, which is more common with Schrader valves. However, you can fix it by removing and cleaning the valve core.

The air leaking from the valve might be fast and easy to notice, depending on the level of damage. However, it might be subtle and tricky to detect. If you have suspicions, there’s an easy test you can perform. 

Rub soap and water on the valve after removing the cap. If bubbles start forming, that means air is leaking from the valve. If there are no bubbles, but you are convinced there is a leak, it could be somewhere else on the tire.

What Happens if You Can’t Find the Leak?

As much as I recommend DIY projects, you can’t fix everything yourself. Sometimes the problem might be evident and easy to fix. However, this isn’t always the case. Some things might be too challenging to be noticed by non-experts. In these cases, you can take it to the nearest bike shop and let them have a look at it.

Final Thoughts

In summary, a small air leakage immediately after removing the pump is completely normal. If you use suitable pumps and take note of your tire pressure regularly, you shouldn’t run into any problems. And, if you do, you’ll notice it very early.

You only have to worry when the air keeps leaking out after you have removed the pump. This might be caused by a damaged valve, as it’s the most common cause. Always check your tires and have fun riding.