Another aspect that influences it is the width of the tire. A 25 (or less) tire will carry a higher pressure than a 28 (or more) as it will have a harder time maintaining the structure of the rubber.
The materials also influence it what is the tire made of, especially the TPI density (Threads per inch) with which it is constructed. A higher number of TPI, less amount of rubber (therefore lighter but more prone to punctures) and more air required. A lower number of TPI (heavier and more resistant) less pressure.
These and other details are what manufacturers use when marking the optimum pressure ranges that each tire can handle. Within them, it is the user who must assess which one suits him best.
You may be interested: When do you need to change the covers?
Tire pressure adapted to the terrain
Although on the road the terrain is much more stable than in the mountains (in short we are talking about 95% of the time it will be asphalt in a very similar state) it is true that we have to adapt the pressure to the type of terrain that we face we will find
If we excessively inflate the wheels we will encounter several problems, the first of which is behavioral. With too much pressure the wheel will bounce a lot when we stand up or when we drive on broken asphalt, potholes, bumps, etc., which in the end results in greater back pain and more accumulated fatigue as the kilometers pass. Besides, over-inflated wheels have a greater tendency to puncture.
If, on the other hand, we have little pressure, we will go much further ballasted (the tire deforms and there is more friction surface with the asphalt), it will be ungovernable in curves and we run the risk of decelerating.
Pressure depending on the weight of the cyclist
There is a standard that serves as an approximation and that, respecting the lower and upper limits set by the manufacturer, can serve as an initial reference. It is necessary to inflate (in bars) a little more than 10% of the weight (in kilograms) of the cyclist. In other words, a 65 kg cyclist must enter a pressure of 6.5-7 bar. If the tire is 25 mm the figure will be a little higher than 7 bar and if the tire is 28 mm it may be a little lower.
Another rule that applies is that the cyclist’s weight is distributed 60% on the rear wheel and 40% on the front, so the most common thing is that we carry a little more pressure behind it. The difference is usually around 0.5 bar more.
However, even if the cyclist is lighter or heavier, it makes no sense (because of the risk involved) to exceed the lower or upper limits marked by the manufacturer. Even if the rider weighs 95 kg, it does not make sense to inflate the wheels much more than 8.5 bar, for example. Or if you weigh 55 kg, bring less pressure of 6-6.5 bar.
In addition, to find the ideal figure, what we have to look for is the lower pressure at which we have ruled out the risks involved (of pinches, of loitering in bends or the feeling of being weighed down).
However, what works best is always to try different pressures and see how the bike behaves. The writer of this article weighs 65 kg and has verified that, with the same tires, on the route and on the asphalt, with 8 bar pressure the behavior of the wheel was the same but it punctured many times more than with a higher pressure low (7 bar).
Tubular and tubeless road
As we said, in this article we have focused on the most common system among cyclists, the camera and cover system. Professionals tend to wear tubulars which, in general, they support higher pressures without so much risk of bursting or puncturing, since they are more reinforced.
Or the tubeless systems (without a tube and with sealing liquid) which, although they are not as introduced as MTB, do have some models on the market. In this case the tires have more reinforced flanks that allow lower pressure to be used (more capacity to absorb vibrations) without being deformed.
Whatever the system, the general notions and risks that we have detailed do not vary whether or not we come up with the pressure we put in relation to what the brand recommends.
You may be interested in: Professionals and tubeless. The pending subject?
On rainy days, cobblestone or dirt
Days of heavy rain tend to be the exception in terms of changing pressures. The lower temperature of the asphalt and the risks of a more slippery surface means that it is better to sin for greater friction than the risk of the tire slipping. In addition, the water brings dirt from the asphalt and increases the possibility of a puncture.
For that it is advisable to wear less pressure than usualdepending on the amounts in which we move between 0.5 bar and 2 bar less (even a little less in the case of tubulars).
The same happens if we drive through areas of cobblestones or ground (which is increasingly common in certain cycling events or experiences such as the Ronde Van Vlaanderen Cyclo or the Gran Fons Strade Bianche). In these cases, in addition to opting for wider tires (a minimum of 28 mm is recommended) a lower pressure than we normally wear to improve the absorption capacity of the wheel and enjoy a certain “comfort” in such a hard terrain.
How is pressure measured?
The two most common measures that we will find on the sides of the tires to indicate the pressure, are the bars (bar – the approximate equivalent of a terrestrial atmosphere at sea level) and the psi (pounds per inch – pounds per square inch). Since the zero is the same in both cases, 1 psi equals 0.07 bar, or what is the same, one bar is 14.5 psi.
How to achieve these pressures? The foot pump is your ally
Every cyclist should have a good one foot pump (or workshop pump) at home. Not only because with them we can give more pressure (and faster) than with hand pumps, but also because we can control the amount of air we introduce into the wheel thanks to the manometer.
You may be interested in: Road Bike Tires: The Keys
The big problem that most hand pumps have is that, mainly due to their smaller size so that they weigh little and can be carried in the jersey or anchored to the frame without disturbing them, they do not reach the optimal pressures that they require road tires. While they may save us en route and allow us to get home, what they won’t take is having to check it at home or at a gas station with a valve adapter.
That is why it is essential to have a foot pump that allows us adjust the pressures before each departure. In addition, most have a double mouth to be able to inflate “presta” and “schrader” valves (which are still used in some MTBs, children’s bikes, urban bikes or trekking bikes).