Tire pressure: what should be and how to pump?

The quality of cycling depends on the pressure in the inflated tire. Insufficient compressed air pressure in the wheels leads to more frequent punctures and breakdowns of the chamber and tire. Excessive - to abrasion of rubber. Optimum tire pressure can be determined based on your experience with proper cycling and manufacturers' recommendations.

The correct tire pressure is a specific parameter for each bike and its rubber. The owner of the bike creates a certain pressure based on the quality of the roads where he rides, or their complete absence. Not the last role is played by riding preferences and physical training. The minimum and maximum pressure is determined by the supplier of the particular rubber.

The increased pressure in the wheels gives the cyclist the opportunity to save power. By improving the movement of the wheels, a person can lengthen or complicate his route.

The pressure that exceeded the limit entered by the manufacturer is the reason for breaking the chamber from the inside of the rim. The side of the rim where the spokes go and where the protective rubber tape runs through will eventually break through the chamber of one of its lateral edges.

Below a smaller limit, pressure will result in a breakdown of the chamber, or “snakebite”. It looks like two adjacent holes. The rim breaks through the camera in two places at once, when the wheel hits an obstacle.

The pressure range of the chamber is indicated on the side of the tire on the side. For example, on a tire for a mountain bike it is indicated that its width is 1.95 inches. Inflate the wheel and measure the width of the tire with a ruler and two squares or a vernier caliper. If the width matches the specified value, and the wheel feels firm and elastic to the touch, then you can ride. On the camera, the width of the inflated wheel is not indicated - in this example, without a tire, it can swell not to 1.95, but, say, to 2.1. When the camera is already "sitting" under the tire, then the nipple itself takes on the load from the air bursting from the inside.

The valve of the nipple - the spool - is reliable enough not to bleed air when the bicycle wheel is standing still in place or when its working load is in the process of riding. The pressure rating during the ride is already taken by the tire, not the camera. The tire does not allow the camera to swell even more. The camera is securely held by the tire due to the shape attached to the entire rubber cord and side cable.

With low pressure, the tire tire misses under the weight of the cyclist. She jammed the camera, leading to abrasion, making it more pierced. Excessive pressure at high speed will break the rubber when hitting a bump, stone, rails or crack across the road, when driving on overheated asphalt.

The pressure in bicycle wheels is measured in pounds per square inch, in pascals and in atmospheres (bars). The atmospheric pressure of the Earth on the verge of ocean level reaches almost 1 bar. This unit also serves as the value multiplied by the coefficient indicated on the wheel. Calculation formula: 1 atm = 101325 Pa = 1 bar. Pounds per square inch is an outdated measure. The bar is also, but it is steadily associated in the memory of people with the value of the pressure of one terrestrial atmosphere (value at sea level). One bar equals approximately 14.5 psi.

The number of bars rarely exceeds 10 units. The number of pounds per square inch is sometimes more than 100. The number of kilopascals is a three-digit (but maybe over a thousand) number. Kilopascals translate to bars or pounds per square inch. According to the above formula, the cyclist and pumps the wheel. Deviation from the recommended range of values ​​will result in high accident rate. You can convert kilopascals to megapascals (MPa) by dividing the number of kilopascals by 1000.

Each tire type has its own pressure standards.

The norm for road bikes is 8-11 atmospheres (bar), depending on the particular tire, the weight of the bike and cyclist, medium and extremely high speed. Here a general rule works: pumping up the pressure recommended by the manufacturer (maximum -0.5 atmospheres), you will quickly and safely get from point A to point B of your route. Squeeze 10 atmospheres with a manual pump is unlikely you can do it. Use a hand or foot pump with a pressure gauge. If your pressure limit is 9.5, then download 9 and drive quietly at maximum speed.

All chambers gradually poison the injected air through their micropores. Part of it is also bleed through the old nipple, loose from thousands of paging. Rubber itself allows molecules and atoms of atmospheric gases to pass through: compare the size of the vulcanized polymer molecules (this is a long chain) that the camera is made of and the sizes of nitrogen and oxygen molecules. The longer you use the same camera, the more it poisons the air - gradual delamination, drying out of the rubber structure does its job. For example, at KAMAZ, wheels pumped due to congestion eventually burst at full speed (one at a time, as the rubber resource is depleted).

A road bike with 10 bars in wheels, traveling 40 kilometers per hour and carrying a biker weighing 80-90 kg, undergoes the same thing. During the week, the working pressure in the wheels drops by about 1.5 atmospheres. Having felt the wheel after a 300-kilometer marathon, you are unlikely to feel that it has lowered, but the pressure gauge of the pump (or automobile compressor) will immediately indicate this.

He pumps up the wheel of the bike in a few seconds, and when the set pressure is reached, the automatics switches off the air blower. The bike owner’s own pump is not only a portable tool that allows you to pump the wheel after repairing rubber. For bicycle professionals, a pump is a means that they use regularly, and often even forcedly. Sports bike destinations - fast riding (up to 40 km / h), racing on the highway and cycle tracks. Pumping its wheels below the average pressure will lead to a quick breakdown of the chambers. An additional problem here is broken, cracked, rough, cracked and bumpy asphalt.

If you pump the wheel of any bicycle 2-3 times higher than the maximum value, then such pressure is guaranteed to explode the chamber with the tire after the first hundred meters of the path. But even if the rubber withstood such pressure, the rim would easily have suffered severe damage. The “upper” pressure is not the one at which the tire bursts, but the one at which the wheel itself will break.

For a teenage or adult road (or mountain) bike with a wheel diameter of 24, 26, 27 and 27.5 inches, the pressure of 2.2-4 bar is considered optimal. But a road bike can withstand tire pressure and up to 5 atmospheres. Exceeding this value will damage the rim on the first bump or explode the camera after acceleration over 30 km / h, sudden braking. A wider rim holds the camera lens better than a narrow rim. The more flexible the tire, the more pressure it may require. And this does not mean that it will break with the maximum value.

Keep a fine line between grip and traction. Inflated to maximum pressure, the tire will roll very well. And yet the clutch will deteriorate sharply, since it is a much lower speed - 5-30 km / h, and not 30-50. With a pressure below 2.2 atmospheres, the tire will noticeably rinse. Maneuverability and balance on bends will also suffer. The first bump, passed at high speed (from 25 km / h) will lead to a "snake" breakdown.

The narrower the tire, the more pressure it will need. The above values ​​for "mountain" and "road" rubber are suitable for a cyclist weight of 80-85 kg. The heavier the rider, the more wear-resistant rubber he needs, as being overweight requires more pressure. For dirt roads, off-road and asphalt, adjustments are also made.

Fat bikes are best suited for riding on sand, snow and rocky roads. An example is winter movement along a road that comes close to a railway embankment and is covered with a snow layer of 10 cm. The running area of ​​a fat bike tire here is 2-3 times wider than that of rubber for a mountain bike or city bike. A large area of ​​contact of the tire with the road brings the fat bike to the wheels of a motorcycle. You can freely ride a bike on the terrain of forests and fields. A table of normal pressure in pounds per square inch is selected for a rider with an average weight of 80 kg.

For lighter or heavier cyclists, the values ​​differ up to 1.5 times from the average. The wheels of a fat bike cannot be inflated to the pressure in the wheels of mountain and especially highway bikes, because this will spoil its handling. Steering at high speed when passing sharp turns will become noticeably more difficult. Creating a pressure below the minimum, you risk losing the nipple: during sharp braking, the camera will scroll in the tire around the rim, the “nipple” will be perforated and the wheel will immediately deflate.

It will no longer be possible to repair a camera with a cut nipple. To ride at low pressure without negative consequences, use tubeless tires. The diameter of the wheel does not matter, only its width and the strips in contact with the road when driving are important.

A semi-slick tire requires close to maximum pressure. The tread of the wheel should only come into contact with asphalt with a running strip without involving the side lugs. They, in turn, are needed only when traveling on dirt roads. Having inflated below average pressure, you make the side strips wear out faster. A smooth road is completely useless for them. The bike will not become more manageable from this.

Cross country bike tires have a width of 2.1–2.3 inches and wheel pressure of 3-4 bar. The grouser strip on each side of the tire is not as aggressive as the half-slick.

Extreme sports enthusiasts riding BMX and Downhill bikes use special tires with a width greater than 2.3 inches. Good tire grip is important here. Loss of traction can end fatally, especially when descending from a steep mountain or hill. The pressure value is determined empirically without significant deviation from the average value set by the manufacturer.

On road bikes, the average value is 9 bar (up to 130 Psi). If the manufacturer is unknown or it is a little-known Chinese company, then the tire does not contain any data on the pressure limits. A tire inflated to a pressure above the limit mark is similar in hardness to something resembling a piece of solid rubber. From this, it undergoes accelerated wear.

This primarily refers to cycling hybrids, “cross-country all-terrain vehicles”, a sort of “custom”, often used by cyclists for multi-day trips and trips. Also, the bike will "goat" - throw you on every bump.

When pumping up wheels, consider a number of factors that can in no way be ignored. It depends on them whether the tire will develop its maximum resource or whether it will fail, having barely passed the minimum distance. Aerobatics - a significant excess of the service life of rubber with the same daily mileage, which has become your habit and lifestyle.

Winter or summer temperature fluctuations can affect tire pressure. There are cases when 8 atmospheres pumped up at home in a forty-degree heat turned into 9.5. This significantly exceeds the average value - the camera breaks through on the very first bump after leaving the house. And in the wheels of a mountain bike, 3.5 atmospheres in a 20-degree frost turn into 2.4.

In winter, owners of road bikes slightly exceed the maximum pressure before leaving. As they pass the first kilometer, the pressure will drop markedly. In summer, on the contrary, cyclists do not pump the wheels a little. When leaving on an overheated road in summer heat, the pressure itself rises to the desired value. In both cases It is necessary to create pressure not exactly, but with a slight deviation.

If you bought an unknown tire for a mountain bike, use the data in the following table. This is a general guideline recommended by experienced cyclists.

For every extra kilogram of the body weight of a cyclist or a load taken on the road, 1% of the total average tire pressure is added. When the bicycle is overloaded and the wheels are pumped over, another threat appears - the “eight” on the rim.

Driving mainly on asphalt, rocky and rolled roads requires a bit more pressure than the average value. The same rule applies for stunt riding on difficult technical tracks. The load from constant shocks and vibration is almost constant here. And to prevent premature abrasion of the camera on the tire cord you need close to maximum pressure. For soft soil, sandy-clay roads, pressure is selected slightly below average.

If the terrain is rough - asphalt, including broken roads, soil of varying degrees of hardness, then the pressure should be pumped at an average level or slightly higher.

Bikers who try to check and correct tire pressure after each ride often do not experience any problems with the wheels for the whole season. This significantly reduces the cost of rubber - it breaks not only from punctures with a careless attitude to pumping wheels. And it does not matter whether you have a sports bike or a regular one, always create the right tire pressure.

See how the tire pressure should be in the video.