Why Do My Bicycle Tires Go Flat Over Time? (What’s The Solution?)

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If you’ve ever had the experience of getting on your bike for a long-overdue cycle…and finding that your tires have gone flat, even though there’s no sign of a puncture, then you might be left wondering why this can happen. We’re going to look at the reasons why and (more importantly) we’re going to look at the solutions. Because, feeling the wind on your face as you pedal along is awesome. Standing in your garage looking at a bike with two flat tires is not.

Why do tires deflate over time?

There are essentially two reasons why bike tires go flat in time. One of these is the real reason and the other makes the problem worse.

The main reason is that the rubber of inner tubes has microscopic holes in it. These are too small to see but just large enough for air molecules to sneak through.

Inner tubes will hold their pressure for a period of time because, when you pump up a tube, you force millions (and probably billions) of individual air molecules into it.

You won’t be able to feel the air molecules escaping through the holes but, as days and weeks go by, you will start to notice that your tube is losing pressure.

why do bike tires deflate over time diagram

(There’s actually another place where tubes can lose air from – often the inner tube valves can be a little leaky too, though the amount of air loss from valves is generally much less than from the larger overall surface area of the rubber tube)

The second issue is that most bikes are kept sitting on their wheels. This doesn’t specifically cause tires to deflate, however the weight of the bike will put extra pressure on the inner tubes and force air molecules to escape a little faster.

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What’s the solution to deflating tires?

So, how can we stop bike tires deflating over time?

Well, we can’t.

Those gas molecules are going to carry on escaping from our inner tubes because the pressure on the inside of the tube is higher than the pressure on the outside of the tube and, well, entropy, yeah?

Everything in the universe is trying to become more evenly distributed: the ice cubes in your (warmer) drink melt, the sugar in your coffee dissolves through the water, on a grander scale the mountains crumble…and, in time, your bike tires go flat.

That said, there are two things that we can do to solve this tricky challenge: keep bikes stored off the floor (with the weight off their tires) and have a bike pump handy.

Storing bikes off the floor

Firstly, we can ‘take a load off’ by storing our bikes so that they don’t have all the weight pressing down onto the tires.

There are two main methods for doing this – either using wall-mounted racks or hooks to hang your bike from or suspending it from the ceiling with a hoist rack.

I’ve got more detail on both these garage storage techniques for bikes here.

Bike tire pumps

So, how do you put air in a bike tire?

You need a bike pump (or, ideally two) so that you can top up your tires when they deflate.

I’ve got more details on my recommendations for bike pumps here, but in essence it’s useful to have:

A floor-standing bike pump for use at home – these will inflate tires quickly (tiring your arms out less!) but aren’t very portable. Check your tire pressure before you leave for a ride and top them up with this if needed.

Because they aren’t portable it’s also useful to have a small pump you can take out with you – you can buy smaller versions of the floor-standing bike pump that attach to your bike. However my favorite is a CO2 tire inflator. These use gas cartridges and can inflate a tire (even a big ‘ole tube on a fat tire electric bike) from flat in just a few seconds.

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It’s a fact of life (or cycling, anyways) that your bike tires are going to deflate over time.

You can’t fight it, though you can slow it down a little by taking the weight off your tires and hanging your bike up on a rack.

Because you can’t fight it, the only viable solution is to have a bike pump handy to keep your tire pressure topped up.

At home, a floor-standing bike pump is the best option.

On the road, either choose a CO2 tire inflator or a frame-mounted bike pump.

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