Getting tire pressure just right can transform how your bicycle commute feels.
Too hard, and you get a harsh ride with poor traction. Too soft, and it’s hard work that wears tires out prematurely.
You should expect some trial and error to get it perfect, but finding a good starting point isn’t hard.
How to find the right tire pressure for your bicycle
No single pressure is best. For city/commuter bicycles, choose the lowest pressure that lets the tire sag slightly (around 15% of its height) when you’re on the bike with full bags/cargo. You can get a good estimate from a tire pressure chart, but remember to stay within the manufacturer’s pressure range.
All else being equal, wider tires need lower pressure and heavier riders/cargo need higher pressure.
That’s why you might personally use different pressures on different bikes. Likewise, two riders would use different pressures on the same bike.
I suggest starting at the bottom of the manufacturer’s pressure range, then adding around 5 psi at a time until you see the 15% tire sag mentioned above.
As a rule of thumb, that makes the tire is soft enough for a smooth ride with good traction, but not so soft that it feels sluggish or wears out prematurely.
Granted, 15% is hard to visualize, so here’s a rough example from the tire manufacturer Schwalbe:
If you don’t want to totally wing it, then you can start with a pressure chart like this popular one. That sort of chart suggests pressure for each wheel separately, so you first need to estimate the weight distribution between front and rear.
That might be an unfamiliar concept, so let’s take a closer look.
Why weight distribution is critical for tire pressure
The front tire generally bears less weight than the rear and should therefore be softer. You’ll want a larger difference on very upright bicycles (like a Dutch-style city bike), since the upright posture shifts your weight rearward. Conversely, road racing bikes may have only slightly softer front tires, since their forward-leaning posture create more equal weight distribution.
Here’s an example.
On a road bike, the balance might be 45% front/55% rear. On an upright city bike with a fully-loaded commuting pannier, let’s assume it’s perhaps 30% front/70% rear.
Of course, those numbers are hypothetical. If you want to use a pressure chart as accurately as possible, then use a bathroom scale to weigh yourself on your fully-loaded bike.
- Load up your normal commuting load, like a pannier or other cargo.
- Put one wheel on the scale and one on the floor.
- Use a wall for balance to sit on the bike, and check the scale’s reading.
- Repeat this with the other wheel.
Let’s say you measured 45 kg with the front wheel on the scale and 55 kg with the rear. That makes 100 kg total, so your weight distribution is:
- 45 / (45 + 55) = 45% front
- 55 / (45 + 55) = 55% rear
Let’s also say you have 37mm tires.
Based on that distribution and tire size, this standard chart recommends 45 psi front and 53 psi rear.
But what if you switch to a very upright Dutch bike?
Now, perhaps, there are just 30 kg on the front wheel but 70 kg on the rear. For the same tire width, the chart suggests 30 psi front and 68 psi rear.
Any rider could feel that large of a difference, so it’s worth taking the time to estimate your own weight distribution at least once.
Why too-soft bike tires wreck your commute
Tire pressure is also a huge factor in ride quality.
The contact patch—that tiny bit of tire that’s touching the ground at any moment—will deform (i.e., squish and flatten to the terrain) and then spring back into shape as the wheels rolls and another patch of tire is now in contact. That happens continuously as you ride.
A lower-pressure tire can deform more, so it creates a bigger contact patch (hence more traction) and can absorb more bumps and vibration (like a sort of micro-suspension).
However, that process of deforming and springing back absorbs some of your momentum.
That’s why lower pressure translates to better grip and a smoother ride…but feels sluggish and resistant if it’s too low.
What’s more, very soft tires will wear out prematurely. After all, that bigger contact patch means more rubber in contact with highly abrasive asphalt.
Additionally, low pressure increases the chance of a “pinch flat.” That happens when a bump compresses tire so hard that the edge of rim slices into the tube.
“All right,” you might be thinking, “I want to ride fast and preserve my tires, so I’ll pump them up good!!”
That’s not entirely wrong, but it’s not that simple, either.
Here’s what happens with too much air in your bike tires
Most cyclists should not pump their tires to their maximum psi.
Firstly, it reduces traction and smoothness. Firmer tires cannot grip the ground nor absorb vibrations as readily as softer ones. We’ll cover this in more detail later on.
As bicycle tires get firmer, the contact patch gets smaller. At some point, this creates perilously poor traction on wet or gravelly stretches. The tires just can’t deform enough to grip the ground well.
This also makes for an extremely harsh ride. It’s too firm to comply with vibrations and bumps, so those get transmitted through the frame and fork rather than absorbed by the tire’s compliance.
Secondly, we’ve seen earlier how rider and cargo positioning affects weight distribution. Even if the rear tire (which bears more weight) actually *did* need the max pressure, the front tire still probably wouldn’t.
Where is the psi on a bike tire?
Every bicycle tire has a psi value printed on its sidewall. That’s the smooth rubber to the left and right of the tread (from the rider’s perspective), where you’ll also find manufacturer logos.
There’s always a max psi number, and often (but not always) a minimum number. These are sometimes embossed in the rubber of the tire, not printed with ink, so you may need a flashlight to see them clearly enough to read.
What’s the best way to check tire pressure?
It’s best to check bicycle tire pressure with a dedicated gauge, which is more accurate than the one built into most pumps. Temperature greatly affects air pressure, so try to check pressure at the same temperature at which you inflated the tire. Note that you’ll lose at least a few psi just by attaching and removing the gauge.
Generally, pressure gauges are most accurate in the middle of their range. For example, a 0-60 psi gauge would be best for tires around 20-40 psi, give or take a bit. Keep your bicycle’s tire pressure in mind when buying a gauge.
Do bicycle tires lose air over time?
Bicycle tires do lose pressure over time, even with brand-new inner tubes. That happens because air molecules are even smaller than the tiny pores in a tube.
Losing more than a few psi each day means it’s probably time for a new tube. The exact number depends on the original tire pressure, since higher starting pressure means greater force pushing those air molecules out.
Personally, I consider replacing the tube if pressure drops by more than about 20% in a couple days.
That’s not a hard and fast rule, though. It depends on how quickly the brand-new tube lost air in the first place.
(For instance, if it used to drop just 5%/week and now drops 20%, we have a problem. If it originally dropped 15%, then I’m not concerned.)
How often should I check my tire pressure?
If you bike commute every day, then check your bicycle’s tire pressure every 2-3 days.
You rely on your bike for safe and easy travel, so it’s important to stay on top of low pressure that could interfere with your commute or important errands.