Without the correct tyre pressure, all the technology of your bike can feel useless, the most promising training sessions, spoiled and your safety, jeopardised.
Tyres are the bike’s point of contact with the terrain and they have significant impact on its behaviour and the performance of the cyclist. The first step is to choose the most suitable tyres and for this, we recommend reading our article on How to choose road bike tyres.
Once you have chosen the right tyre, it is equally important to set the correct pressure as this can modify tyre behaviour: increasing the pressure reduces tyre deformation and, as a consequence, friction, making the tyre faster, but with reduced grip and comfort. High pressure prevents the tyre from adapting to the terrain and any unevenness will cause the tyre to bounce. Lower pressures, on the other hand, increase grip and comfort, to the detriment of speed. So, it is a question of finding the right balance and that will depend on several factors such as the cyclist's weight, the type and width of the tyres or the road conditions. Here, we will take a look at each of these factors to help you define your needs and decide on the appropriate tyre pressure.
We recommend you start by applying a generally accepted rule for calculating tyre pressure on road bikes: the 10% rule, which recommends calculating 10% of your body weight and using this number as the tyre pressure in kilograms or in bars, which is practically the same thing. The difference between these two units is not significant for the accuracy required, in this case. To convert these measurements into psi (pounds per inch), just multiply them by 14.5. The following chart gives the bar and psi pressure equivalences for road and tubular tyres.
This rule of thumb is a guideline that may need to be customised, depending on your circumstances, and always respecting the minimum and maximum pressure limits set by the manufacturer. In general, it is not recommended to go below 6 kilos of pressure, even if the cyclist weighs less than 60 kg, nor to exceed 8.5 - 8.6 bar, except with tubulars or special tyres, as we will see later. But we insist that the limits set by the manufacturer should be respected.
Tyre width is the first factor to take into account for customisation, as a wider tyre requires less pressure to maintain its footprint without deformation.
In our experience, we prefer to apply 10% of our body weight in bars to 25 mm tyres, with an additional 0.5 bar on the rear wheel, which carries around 60% of body weight. On 23 mm tyres, we recommend raising the pressure by 0.3 - 0.5 bars, depending on the rider's weight, and lowering it by the same percentage on 28 mm tyres. These recommendations are for dry roads with a good road surface, which will give a good grip.
For uneven or wet terrain, we recommend lowering the pressure by at least 0.5 bar - 1 bar if you are riding on rough terrain, dirt, cobblestones or in constant rain, and up to 2 bars on tubular tyres with over 9 bar pressure. The lower pressure will enhance grip and cushion a fair amount of impact and vibration. And, if you frequently ride on this type of terrain, we highly recommend 28 mm tyres.
Peter Sagan and Specialized Paris-Roubaix 2018A common mistake made by road cyclists is to set air pressure too high in order to increase speed. But the difference in performance is smaller than you think, compared to the recommended pressure, and does not usually compensate for the loss of grip, comfort and the higher risk of punctures. On uneven terrain, too high pressure can also penalise speed, as the tyres do not follow the terrain and are constantly bumping and bouncing around, which slows the bike down.
Tubeless tyres are compatible with lower air pressure, thanks to the reinforced sidewalls, which means they are more resistant to deformation. You can easily ride on 0.5 bar lower pressure than that used for tube tyres.
Tubular tyres, which are still the most widely used for competition, are compatible with high pressure, which ensures little tyre deformation and low rolling resistance. The special composition of these tyres makes them comfortable and resistant to punctures, in spite of their high pressure. However, the difficulty of mounting and repairing a tubular tyre on the road, limits their use outside competition.
By taking these factors into account, you can determine the most suitable pressure your road bike wheels at any given moment, but the best reference will always be your experience. Do not be afraid to try out different pressures, without taking unnecessary risks and always within the limits recommended by the manufacturer.
The high pressure of road tyres cannot be reached with just any pump and just feeling the pressure of a road tyre is not recommended. Above a certain pressure, it is not easy to perceive the difference in pressure by touch and you will need a pressure gauge to measure it correctly. This either comes included in the bike pump or separately.
Reaching the recommended road tyre pressure requires an inflation system that exceeds 10-11 bars max. pressure. This is easily achieved with a foot pump, compressor or CO2 cylinder. However, mini pumps are more difficult and will not exceed 5 bars, unless you use one specially designed for road use. In this case, if you do not have a CO2 cylinder, you will have to complete the inflation at the nearest gas station. Remember to always carry a presta valve adapter.
See more tips on inflating tyres in these videos from our Youtube Channel:
And you can find professional help and advice as well as a huge range of products by top brands at our Mammoth stores and online at mammothbikes.com/en/.
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