Bike tire keeps going flat but without puncture

Having a problem and not knowing the solution is frustrating, to say the least. A bike tire that does not show any signs of puncture and keeps going flat falls into that category.

There are many reasons for a bike tire to not hold air, from tiny punctures, valve damage, rim deformation, or even faulty rim strips.

Here’s the breakdown of all the possible causes of a tire’s air leakage.

Inner tube puncture

This cause is by far the most common. Inner tubes are made of rubber to be lightweight, but this comes at a cost: it’s not so durable. Some debris or something else sharp went through the wheel and pierced the inner tube. You may not hear or see the punctured area of your inner tube.

A way to try to see the leakage is by submerging the inner tube into water and look for bubbles. After replacing or patching, be sure to check the interior of the wheel to be sure the culprit of the puncture is not around to do some extra damage.

Tubeless wheel puncture

Without the inner tube to have to worry about you still could have some things to be looking at. While highly unlikely, you still may have a puncture in your tubeless setup. Check your wheel thoroughly for a significantly larger hole.

There is a possibility that your bike tire keeps going flat but without puncture. Below are all the other options of a possible bike tire losing air.

Valve leakage

While a valve should never get damaged, real-life use is far from ideal. Dirt or improper tire pressure may loosen the seal of the valve and create a gap. The best way to check would be again with the water submerging method.

Rim deformation

The culprit may be closer than you think. A small deformation may pass as unnoticed and create a sharp angle for the inner tube to become punctured. In the case of tubeless tires, even a small deformation can create gaps that further increase the occurrence of tire burping.

That’s when the lateral forces move the tire and creates gaps. You can read more about it here.

Faulty rim strip

As this article suggests, you may be looking at a rim strip replacement. You may have either too narrow, damaged, or moved the strip while installing a new tire without even noticing. Having gaps means the tube is not perfectly sealed or worse, it lets spoke nipples be in contact with inner tubes.

Time

Your tire is not perfectly sealed as it is made of rubber. A substance that is porous, meaning that air can and will pass through and over time your tire will become deflated. (read more diffusion)

Conclusion

Having a bike tire losing air is a bad thing to have. Finding out the culprit will require you to take all the options one by one. There is no way around it. Have patience and inspect thoroughly.