Regardless of whether you’re cycling on mountain trails, flat roads, or gravel roads with a gravel bike, you’ve likely made the most common mistake among cyclists at least once: not inflating your tires properly. Sometimes, there’s a tendency to overinflate, thinking that increasing tire pressure will lead to higher speeds. Or there’s the common misconception that tires are airtight and only lose air due to punctures. But that’s not the truth.
Having rock-hard wheels doesn’t necessarily mean achieving higher speeds, and for safety reasons, it’s always important to ensure that your tires are inflated to the correct pressure, taking into account the rider’s weight, tire width, and other factors. But I won’t delve into too many details just yet, so let’s start with the basics:
To determine tire pressure, you’ll need a pump equipped with a pressure gauge, whether it’s digital or analog. It’s even better to use a separate pressure gauge since many built-in gauges on pumps read the pressure inside the pump itself rather than that of the inner tube.
The two most common units of measurement for pressure are PSI and bar. In the past, atmospheres were often used in Italy as a unit of measurement, but it’s now uncommon. In this article, we’ll use PSI, but we’ll also provide a conversion table to facilitate the conversion to bar:
Using this information, you will be able to easily find the equivalent value in bar from PSI.
All tires, as well as many rims, have a recommended pressure range or maximum value specified by the manufacturer, indicated on the tire sidewall and/or rim profile. This value is expressed in PSI or bar. For safety reasons, these values are often conservative, but it is still advisable to closely follow them to avoid any unpleasant incidents.
In the absence of specific information regarding the tire and rim, below are the recommended pressure levels for a cyclist weighing 70 kg:
There are several factors that influence the optimal tire pressure for a bicycle, but let’s look at the six main ones:
Tire Width: If the tire is wider, a lower pressure will be required. This is because pressure is the measure of force exerted by weight on a surface. So, with a larger surface area (as in the case of a wider tire), a lower pressure will be needed for the tire to fit properly on the rim.
Tire Casing: The internal construction of the tire, known as the casing, affects the tire’s resistance and deformability. A stiffer casing will require slightly higher pressure compared to a more flexible casing.
Tubeless System: In the case of a tubeless system, where the tire fits onto the rim without the use of an inner tube, the optimal pressure may be slightly lower compared to a system with an inner tube. However, it is important to follow the manufacturer’s guidelines for best results.
Rider’s Weight + Equipment/Load and its Distribution: The weight of the cyclist and the load they carry influence tire pressure. Heavier cyclists may require slightly higher pressure to avoid pinch flats or excessive deformation. Additionally, the distribution of weight between the front and rear of the bike can affect the ideal tire pressure.
Terrain: The type of terrain you ride on has an impact on tire pressure. On technical or rough terrain, it may be necessary to slightly reduce the pressure to increase grip and control.
Weather Conditions and Temperature: Weather conditions, such as temperature, can influence tire pressure. The air inside the tires tends to expand with heat, so it may be necessary to adjust the pressure based on the weather conditions.
Remember that these are just general guidelines, and you may need to experiment with tire pressure to find what works best for your personal needs and specific riding conditions. Always follow the manufacturer’s recommendations for the tire and rim to achieve the best results.
Tires are available with different carcasses, such as cotton or high thread count (TPI) options. Tires with a lightweight carcass and high TPI are more flexible and faster. On the other hand, tires with a lower TPI are heavier, stiffer, and more durable, offering greater puncture resistance. It is logical to assume that a tire with a high TPI provides superior performance and increased puncture resistance when inflated to a higher pressure. Conversely, a lower TPI allows for reduced pressure to improve grip and vibration absorption without increasing the risk of punctures.
With tubeless tires, it is possible to lower the air pressure for increased grip and comfort without worrying about pinch flats. Additionally, the absence of friction between the inner tube and the tire means that tubeless tires can achieve higher speeds compared to those with inner tubes at the same pressure.
Rider weight + Equipment/Load and its Distribution
The weight of the cyclist and the load carried on the bike are important factors in determining the optimal tire pressure. The heavier the cyclist, the higher the pressure required. You can consider adding or subtracting approximately 2 PSI for every 5 kg increase or decrease in weight for road bikes, and 1 PSI for MTBs, hybrid bikes, and gravel bikes. Always remember to stay within the manufacturer’s recommended minimum and maximum range.
The rider’s position on the bike results in a weight distribution of approximately 60-70% on the rear wheel. Therefore, it is advisable to slightly reduce the pressure in the front tire compared to the rear tire. In general, the pressure difference should be around 2-3 PSI, but this value can vary depending on the riding position, cycling discipline, and pedaling style.
On smooth and paved roads, it is possible to reach the maximum recommended pressure indicated on the tire (compatible with the weight). However, it is rare to find perfectly smooth and even roads. To avoid feeling every bump and improve efficiency and comfort, it is advisable to opt for a pressure between 90 and 100 PSI. This way, the tire will be faster and offer superior comfort, better absorbing roughness and vibrations of the terrain, while also providing increased cornering grip.
For MTBs and gravel bikes, the situation becomes more complicated as the terrain can vary significantly. In this case, it is advisable to experiment. It is better to start with a higher pressure and then reduce it, paying attention to the sensations while riding to find the appropriate pressure for different types of terrain. The key is to find a balance between puncture resistance, grip, and comfort without compromising speed.
Weather and Temperature
It is known that in rainy conditions, it is advisable to slightly reduce tire pressure, but without exaggeration. Reducing 2-3 PSI from the correct pressure for your tires, your weight, and the terrain you are facing will be sufficient. Excessive reduction in pressure can compromise stability and reduce grip instead of improving it. It also increases the risk of punctures, especially for inner tube tires.
When encountering mud, a tread with high, wide, and well-spaced knobs is as important as reducing the pressure.
Temperature also plays an important role, especially when there is a significant difference between internal and external temperatures. The hotter it is, the more the pressure increases, and vice versa. For every 5 °C variation, you gain or lose 1 PSI. For example, if you inflate the tires at home at 21.1 °C and find yourself in an environment with an external temperature of 0 °C, the tires will lose approximately 4 PSI.
Five of these six factors can be taken into account using SRAM’s online calculator to find the optimal tire pressure.
HOW TIRE PRESSURE AFFECTS PERFORMANCE
Incorrect tire pressure, whether too high or too low, can compromise performance in terms of grip, comfort, rolling resistance, and puncture resistance. Since tires are the only point of contact with the ground, performance directly affects both the bike and the rider.
We have already discussed this throughout the article, but to summarize, here are the advantages and disadvantages of using low or high tire pressure:
Low Pressure Advantages:
Improved traction Increased grip Greater comfort Lower rolling resistance on rough terrain
Higher likelihood of pinch flats with tubes
Higher rolling resistance on smooth surfaces and asphalt
High Pressure Advantages:
Reduced likelihood of flats
Lower rolling resistance on smooth surfaces or asphalt
Reduced grip and traction Less comfort
Energy loss on rough terrain
Each cyclist needs to find the optimal tire pressure and strive to balance grip, comfort, rolling resistance, and puncture resistance.
If one aspect is prioritized, there will be a trade-off in another. While tires, rims, and cycling gear in general are constantly evolving, offering performance that was unthinkable a few years ago, tire pressure remains an important factor. Each of us can and should experiment with different pressures in different circumstances. Through trial and error, we learn, because air is free.