Bicycle tyre pressure calculator
Finding the right pressure for your bike tires is not an exact science, but it is one of the most important adjustments to improve your rides. Overinflated, your bike will bounce, lose grip, and become uncomfortable. Underinflated, you risk pinch flats and lose efficiency (feeling sluggish).
The ideal pressure depends on several factors: total weight (you + bike + equipment), tire width, mounting type (inner tube or tubeless), your riding style, and the surface you ride on.
Table of Contents
City Bikes and Commuting
In urban environments, the watchwords are reliability and comfort. Sidewalks, potholes, and cobblestones require a pressure that allows the tire to deform slightly to absorb shocks, without risking damage to the rim.
Tips for urban pressure and e-bikes
City bike tires are often equipped with thick anti-puncture strips. They require special attention, especially with the rise of e-bikes (electric bikes):
- Manage the extra weight: An e-bike often weighs between 20 and 25 kg. Don't forget to include this weight (as well as your bags) in the calculation. A loaded bike always requires 0.2 to 0.4 bar more at the rear.
- Avoid underinflation: In the city, an underinflated tire is the main cause of punctures (pinch flats against a curb). It also prematurely wears the tire sidewalls and reduces the battery life of your e-bike.
- Regular checks: Standard valves naturally lose pressure. Check your city bike tires at least every two weeks.
Mountain Bike (MTB)
For MTB, pressure is vital for grip. The goal is to ride with the lowest possible pressure so that the knobs conform to the terrain (roots, rocks, mud). Today, tubeless mounting is the standard, as it allows going below 1.5 bar without risking a pinch flat.
Adjusting for your MTB discipline
MTB encompasses very different disciplines, each requiring specific tire pressure settings:
- Cross-Country (XC): Efficiency is the priority. Tires are often narrower (2.10" to 2.25"). A slightly higher pressure is accepted to limit rolling resistance on smooth sections.
- All-Mountain / Trail: The ideal compromise. Tires from 2.30" to 2.40", seeking the perfect balance between downhill grip and pedaling efficiency.
- Enduro and Downhill (DH): Absolute priority to grip and rim protection against big impacts. Tires are wide (2.40" to 2.60") with very rigid casings (e.g., Double Down). Pressure is low, but the tire holds up thanks to its reinforced structure.
- "Plus" format (2.60" and 2.80"): These large air volumes allow for extremely low pressures (sometimes around 1.0 or 1.1 bar) for phenomenal grip, especially appreciated on e-MTBs.
Road Bike
The myth of the tire inflated to 8 bar for speed is over. Modern studies show that a slightly wider tire (28 mm or 30 mm) inflated between 4 and 6 bar offers better efficiency. Why? Because instead of bouncing on the micro-imperfections of the road (which slows the bike), the tire absorbs vibrations.
The evolution of road standards
The professional peloton has driven a major change in recent years:
- The end of 23 mm: Historically, riders used 23 mm overinflated tires. Today, the standard is 28 mm, or even 30 mm for classic races. The larger air volume allows for lower pressure, reducing muscle fatigue caused by vibrations.
- The tubeless revolution: By eliminating internal friction between the inner tube and the tire, tubeless road mounting improves rolling resistance while allowing for lower pressures (ideal on wet roads).
- The 10% rule: An old empirical method was to inflate to 10% of your weight (e.g., 7 bar for 70 kg). Forget this rule! It is no longer valid with modern tires wider than 25 mm.
Gravel Bike
Gravel is the art of compromise. You need a tire firm enough to ride fast on asphalt, but soft enough to grip on dirt and filter out pebbles. The classic width ranges from 38 to 45 mm. Here, tubeless mounting is almost mandatory for performance and safety.
The perfect balance for bikepacking and gravel
Pressure in gravel will radically change the character of your bike:
- The notion of "sag" (deflection): A good gravel tire at the right pressure should sag slightly when you get on the bike. This sag of about 15% maximizes the contact patch for traction.
- Adjustment during the ride: Many "gravelists" start with a slightly higher pressure for the initial road kilometers, then let out a little air (by pressing the valve) when reaching rough trails.
- Impact of bikepacking: If you load your bike with bags, don't forget to add this weight to the calculation. Distribute the pressure: if your bags are at the rear, slightly increase the rear tire pressure to compensate for deformation.
How is the ideal bike tire pressure calculated?
The perfect pressure is not chosen at random. Algorithms (like the one used on this page) are based on the laws of physics applied to cycling, particularly fluid dynamics and load-bearing capacity.
Here are the principles governing our formulas:
- Volume law: The wider a tire, the more air it contains. To support a given weight, a large volume of air requires much lower pressure. This is why a 60 mm MTB tire needs less than 2 bar, while a 25 mm road tire will require 6 bar.
- Weight distribution (40/60): On a standard bike, the weight is not distributed 50/50. About 40% of the weight rests on the front wheel, and 60% on the rear wheel (since the cyclist sits close to the rear axle). This is why the rear tire should always be slightly more inflated than the front tire.
- Impact of tubeless: Without an inner tube, the tire works more smoothly. You can (and should) reduce the pressure by about 10% compared to a "tubetype" setup to fully benefit from the system without risking the tire coming off the rim.
What are the differences between Bar and PSI?
When you use a floor pump, the gauge usually displays two units of measurement: Bar and PSI. But what do they mean?
- Bar: This is the most commonly used metric unit in Europe. 1 Bar is approximately equal to atmospheric pressure at sea level (i.e., 1 kg/cm²). It is easy to read because the numbers are small (e.g., 2.5 Bar).
- PSI (Pounds per Square Inch): This is the imperial (Anglo-Saxon) unit, meaning "pound-force per square inch". It is very precise for low pressures, making it extremely popular in the MTB and gravel world where adjustments are made to the tenth.
Now that you know the ideal pressure, equip yourself with the best tires for your practice on Alltricks:
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