If the bike has been sitting idle for months, we always pump the tires before we take it out for a ride. We kind of expect the tire to lose air pressure.
It’s quite normal in older tires, even if there are no identifiable punctures. But if you find your regularly used bike with half the air pressure you left it last night, it’s far from normal.
So, the bike tire loses air overnight. What could cause it? It can be the result of a few things which include but are not limited to damaged tires or overfilled tires.
Since you’re here reading this article, I can safely assume you’re facing exactly this issue. Then, don’t worry. I will attempt to discuss and identify the probable causes behind the bike tire losing air.
Bike Tire Losing Air? What’s Normal and What’s Not?
There doesn’t have to be a leak or a puncture on the tubes to lose air. Any normal tire, even the brand new ones, will lose air over time. Air can pass through gaps of the size of a molecule, and a noticeable amount of air could be lost over a few days.
Narrow tires lose air faster than wider and thicker tires.
According to Oaks & Spokes, you can notice a normal thin road bike tire lose half of its air pressure in just two days. The mountain bike tire, due to the larger air volume, is in a safer position. Normally it’d take 1 week before you can see a noticeable change in pressure.
So, losing 15-20 psi pressure in one night is considered normal in the industry and the community.
But if you’re losing like 50psi in one night, that is out of the normal.
Quick Comparison Between Tire Types and Their Normal Pressure Loss
|Bikes||Typical Tire Width||Usually recommended pressure range||Pressure loss per week||Check pressure|
|Road Bikes||23-28 mm||100+ psi (7+ bar)||5 – 40 psi (0.3–2.7 bar)||Every few days|
|Hybrid Bikes||28-38 mm||80-100 psi (5.5 – 7 bar)||3 – 30 (0.2–2 bar)||Every two weeks|
|Trekking Bikes||35 – 45 mm||35 – 80 psi (2.5 – 5.5 bar)||2 – 25 psi (0.1– .7 bar)||Every two – three weeks|
|Mountain Bikes||40+ mm||20 – 35 psi (1.4 – 25. bar)||1 – 15 psi (0.05– bar)||Every three – four weeks|
How Does the Bike Tire Lose Air?
There are two things I can name as probable cause. Here’s what I think:
The inner tube’s quality is crucial to holding the air pressure. For example, Butyl tubes are known to be quite good at handling air pressure, and they can contain larger molecules.
Oxygen, however, is uncontainable. But even if it does get out, air pressure decreases very slowly.
It can be even worse if you use a CO2 canister since it degrades the tube structure and makes it lose air faster.
If the tubes are made of latex, their thinness allows them to lose air much quicker.
Through the Valve
It’s quite common for the tire to lose air through the valve. Good valves are designed to let out excess air to stabilize the air pressure. And tiny molecules in the air inside can easily find their way out.
How Your Bike Tire Loses Air Overnight
Here’s what I think:
Slow Punctures in the Tube
There is a type of puncture that the cyclists like to call “a slow puncture”. It’s something you can’t see with the naked eye. But it’s just big enough to let the air out quicker than normal. It lets air out slowly without you finding it out.
Leak besides the Valve
This is a common issue. The area where the tube and valve joined together is weak. And as time passes, with more pumping, this area starts to give out. If you exceed the maximum air pressure limit, leaks are the first thing to happen.
It can also happen if you didn’t place the valve correctly. However, this can only be a one-time occurrence. If losing is a daily thing, misplaced valves can be ruled out as the cause.
So, that is why I think your bike tire loses air overnight. Don’t let it linger for more than a couple of days. If you do, leaks and puncture holes will slowly become larger, which will render the tire unrepairable and useless. Take it to a professional to get it checked out.