The wheels of a road bike are inflated almost to the upper limit specified by the tire manufacturer, before reaching 0.2-0.4 atm. This difference guarantees the safety of the tire from bursting when the temperature and pressure rise.
A mountain bike requires an individual selection of the parameters of the normal air pressure in the wheels, depending on the weight of the rider and the terrain of movement. Experimentally, taking a pump with a pressure gauge with you on a trip, you need to find the pressure at which the balance between coasting and grip will be the best.
Important! Do not exceed the maximum or lower the minimum recommended for your tires.
Here it is necessary to clarify a little what BAR, PSI and kPa are.
- BAR is the pressure in bars or atmospheres. For our people, the most understandable designation. It is used in many countries, including the post-Soviet space. 1 BAR = 1 atmosphere
- When the pressure in BAR is multiplied by 100, the result is kilopascals. In this case, it will be 250 and 420 kilopascals. Pascals are denoted by English letters “Pa” or if in kilo. then kPa. They sometimes do the same, indicate the minimum and maximum pressure for which the tire is designed.
- PSI (pound-force per square inch). pressure in pounds per square inch. Used in Europe and some American states. It is designated as PSI or LBS / IN 2. For the given example, these are 36 and 60, respectively.
Pumping Up Bicycle Tires
The relationship between BAR, PSI and Pa is as follows:
1 Bar = 1 atmosphere = 100,000 Pa (100 kPa) = 14.504 Psi,
With Bar and Pascals everything is simple, but with the translation of Bar to PSI everything is a little more complicated, so here is a table for quickly converting pressure in bicycle tires from Bar to PSI and vice versa:
We will mention another designation for pressure, which is called a kilogram of force per square centimeter or technical atmosphere and is denoted as kgf / cm² or kgf / cm². It is quite rare, but it happens. We will dwell on the technical nuances, there are a lot of articles on this topic on the Internet, let’s just say that for a bicycle pressure it can be considered equal to 1 Bar or one atmosphere.
And for lovers of exact mathematics, here are the conversion factors:
1 kgf / cm² = 1 atmosphere = 0.98 Bar = 98.07 kPa = 14.22 PSI
When pumping up a tire, you need to clearly understand that the pressure in it should not be lower than the minimum specified and higher than the maximum. It is worth noting here that it is better to leave a small margin of 0.2-0.5 atmospheres, without pumping the tire to the maximum value so that it does not burst, especially in hot weather.
About what else the manufacturer writes on bicycle tires, as well as what other numbers mean, there is a separate article on it on our website, which is called What do the numbers on bicycle tires mean?
Pumping up bicycle tyres. valve problems
What do they write on the tires? For example, (2.38-4.0) is clearly atmospheres, or BAR, and (95-135) is Psi. If the figure has more than 3 digits or the prefix k (kilo), we are talking about metric Pascal. Most often, the desired value is located under the size designation and is duplicated in BAR and Psi in the form of a range, clearly indicating to what pressure you can pump.
Actually, the manufacturer specifies the range within which the tire can function, then. the freedom of the cyclist.
How often to check the pressure at the bicycle wheels
How often to inflate the wheels of a bicycle is an individual question, and depends on the type of bike, its age, riding style, surfaces on which it is used. If the bike is new, mountain, routes within the city, on decent asphalt, without elements of extreme, the pressure can be checked no more than once a month.
On average, the recommendations are as follows. for a mountain bike it will not be superfluous to check the pressure every couple of weeks, for a road bike it is better to do this every day. In the event of a puncture, the low pressure can be observed visually, and it will be quite difficult to ride such a bike.
With the experience of riding, the feeling of the bike comes, and how much the pressure in the tires of the bike corresponds to the norm will be clear almost immediately. Reduced pressure is characterized, first of all, by too soft a ride, bumps are well swallowed and when driving, even on not too good roads, bumps are practically not felt, while maintaining the speed is much more effort.
Bicycle tire pressure versus cyclist weight
This should be immediately clarified. The pressure in the tires of a road bike always varies between 6.5-9 BAR (up to 130 PSI) and does not depend very much on the weight of the cyclist.
The pressure in mountain bikes is always lower.
Here is a table showing the dependence of the pressure in the wheels of a mountain and city bike on the weight of the biker:
How To: Pump Up Your Bike Tires
You can focus on the following. for each additional kilogram of weight, the pressure should be increased by 1%.
The pressure in the tire directly affects its durability. Riding on badly inflated tires wears them out quickly.
Bicycle tire pressure, calculating the optimum value for bicycle wheels
Seasonal adjustments are quite serious, mainly related to mountain bikes. In the summer, you should slightly underestimate the pumping and not rest on the maximum. Hot asphalt also heats up the air inside the chamber, which increases the volume and therefore the pressure. Also, a pumped tire wears out very quickly.
In winter, you should sometimes slightly exceed the maximum in order to achieve maximum work from the tread, especially if the rubber is selected with spikes.