You’ve just come back from a long vacation and you’re eager to go for a ride on your bike. So you go to the garage, dust off the seat, and get on the bike, only to find that there’s no air left in the tires.
Why do bike tires go flat from sitting?
All bicycle tires lose air while sitting, even if they’re brand new and without punctures. Thinner tires tend to lose pressure faster, so you should top up the tires once a week on a road bike and once every two weeks on a mountain bike.
The rate at which your tires go flat from sitting is an indicator of if your bike’s tires are okay or they need to be sealed, patched, or replaced.
For example, it’s normal for tires to be soft and squishy if you haven’t topped them up for a few weeks. And, in such a case, you need to inflate them before you get on the bike. Empty tires lead to snakebite punctures (when the tube gets pinched between the tire and the rim).
But if one or both of your bike’s tires go flat on you the day after you’ve filled them with air…
You’ll probably need to walk to the bike store and buy a few patches.
Why Do Bike Tires Go Flat When Sitting Unused?
Bike tires lose air due to a few different storage factors. The way you store your bike, the age and condition of the tire, and the outside temperature will all affect how quickly your tires lose air.
You may be surprised to know that even if your bicycle tire is in perfect condition and your tires are 99.9% airtight, they can still lose a small amount of air everyday.
This is because air molecules are tiny enough to escape through the pores of the inner tube or the tubeless tire, the gap between the tire and the rim, and through the valve. No tire is 100% airtight, and a good bike pump is one of the most essential pieces of gear for every cyclist.
In fact, it is perfectly normal for a bike tire to lose 1-30 PSI every day!
When your bike’s resting on the tire, this happens faster. The reason for this is simple, and it’s called gravity. The force of gravity combines with the weight of the bike and presses down on the tire.
Where in My Tires Does Air Escape From?
As we discussed, air can leave a bike tire through the pores in the tire itself, the gap between the tire and the rim, as well as through the valve.
One reason for this might be if your bike tire has a minuscule puncture, or many of them. These holes are almost always impossible to spot, but enough of them can cause a full bike tire to deflate within days, sometimes hours, of sitting unused.
The second common reason is that your rim may have a ding or dent somewhere. Dings and dents make the wheel’s rotation uneven, making it harder for your tire to hold air.
Last but not least, there are valve problems. Your bike’s tires can lose air quickly if the valve isn’t closed all the way, you’ve over-tightened it (forcing the pin down and causing air to escape), or the cap has fallen off and dirt has gotten into the valve.
Will Filling My Bike’s Tires With N2 or CO2 Fix This?
There’s a heated debate among cyclists about whether it’s worth the hassle and money to inflate your bike’s tires with carbon dioxide (CO2) or nitrogen (N2). But the science behind it is sound.
Instead of filling the tires with air, you can inflate them with CO2 or N2.
Air consists of nitrogen, oxygen, carbon dioxide, water, and a number of other compounds in varying amounts. By themselves, CO2 and N2 are denser than air and their molecules take longer to escape through the pores of your tires.
(Exactly how much longer it takes and whether you can feel a difference that justifies the price is a whole other story. Besides, if your tire, tube, and/or rim are damaged, you will get flats anyway.)
The type of gas being used will affect the rate at which your bike tire deflates. CO2 is a really small gas molecule, which means it is able to leak from the tire quicker. CO2 also deteriorates the rubber in the tire at a faster rate.
Although N2 is less common to use, it is a larger molecule than CO2, which means it doesn’t escape the tire as quickly.
Which Type of Bike Tire Retains The Most Air?
|Tire||Inner Tube||Air Retention|
|Clincher tire||Butyl rubber tube||Poor|
|Clincher tire||Latex rubber tuber||Medium|
Clincher tires have tubes made of butyl rubber or latex. Butyl rubber tubes are best for commuter and recreational bikes because they’re puncture resistant and lose air more slowly. Latex inner tubes are ideal for racing because they’re lighter (but lose pressure faster).
There’s good reason why we install tubeless tires on mountain bikes, and it’s because they fit tightly against the rim, lose pressure much slower than clinchers with tubes, and can be repaired easily—including in extreme conditions—with slime sealant.
How Does Weather Affect The Rate That Bike Tires Flatten?
Bicycles are meant to be used.
If you use your bike frequently, you may notice that your tires do not deflate very often. This is because when air heats up, the molecules expand. If you use your bike frequently, it will often keep a more consistent tire pressure and ensure that they retain their air for longer.
However, just like heat causes the air molecules to expand, cold makes them contract. And when the air molecules contract, the pressure in the tires reduces and the tire deflates.
So, if you’re someone who rides during late fall, winter, and early spring, keep your bike pump handy and be prepared to inflate your tires more often to keep pinch flats to an absolute minimum.
Can I Prevent My Bike From Losing Air In Storage?
The good news is that there are a few different steps you can take depending on the issue with your bike to help prevent your tire from deflating as quickly.
Perhaps the most obvious answer would be to stop storing your bicycle on it’s tires. There are a variety of different storage options for bikes that allow you to hang them. This will stop the weight of the bike from accelerating the rate that air escapes.
Consider covering your bike with a tarp if you won’t be using it for an extended period of time to prevent deterioration. If possible, consider keeping your bike in a temperature controlled room. This will help keep the air molecules expanded in the tire.
Make sure your tires are full before you store your bike for an extended period of time. This will help prevent your bike from developing flat spots and other tire deformations.
As we’ve learned, bike tires absolutely can go flat when they are in storage.
Although bike tires are fairly durable, air is able to escape from even the most airtight containers. While there are certain things you can do to prevent air from escaping your bike tires as quickly, this is not an issue that cyclists will ever see disappear.
For now, remember to maintain your bike and check that all of the parts are in good condition, and consider replacing old bike tires that are losing air too quickly.
Serious cyclists should consider investing in a good bike rack to keep the weight off their tires and make sure they don’t get flat spots.
Proper storage of your bike can save you time and money in the long run. It means less last-minute air pumps and tire replacement after riding on a flat tire.