There are many reasons why people buy a bike. Regardless of the purpose of this vehicle, its most important element is tires, which quite often have to be changed. What they are and how to choose them correctly can be found in this article.
Standard tire parameters
The size of the wheels (rim) is a determining factor, because it depends on them for what purpose a bicycle is suitable. Previously, when selecting bicycle tires, they were guided only by the external size of the circle, but over time, a fairly large number of manufacturers appeared in the world, resulting in confusion. In order to make it easier to navigate in the types of tires and choose them correctly for your bikes, it was developed unified system of standards.
It was developed by the international standardization organization ISO, previously known as ETRO. According to this system, the tire width, inner and outer rim diameters and height are taken into account.
These parameters are directly dependent on the year of manufacture, manufacturer and, of course, the purpose of the bike.
Children's bicycles, runbikes, scooters and some folding structures usually have an outer rim diameter of 12 to 24 inches. For adult models, this setting is between 26–28 inches.
The inner diameter of the rim, or, as it is also called, the landing diameter, is the most important parameter for the tire, since it must coincide with the inner width of the rim of the bicycle.
According to ISO standards, the inner tire size is closely related not only to the outer diameter, but also to the width.It, depending on the purpose of the tire, can vary between 18–75 mm.
There is a table in which tire parameters are indicated in accordance with the manufactured bicycle models and their purpose.
For two-wheeled vehicles made in France and in some other European countries, there is a own correspondence table in which the designations of the inner and outer diameters, widths and heights have a slightly different look.
What does labeling mean?
Marking on tires is almost always on the side.
Most often, dimensions are indicated in millimeters. Marking in the form of two numbers, such as 35-559, or 37-630, indicates the width and inner diameter (landing rim) of the tire. The first number is the width, and the second is the diameter.
Sometimes the marking has a slightly different look, and the numbers are indicated in it, not only in millimeters, but also in inches. For example, a combination of numbers like 622x19 indicates the inside diameter in millimeters and the outside size of the part in inches.
Tires can also be marked with numbers only in inches. The view 24x1 ⅛ means that the number 24 is the outer diameter, and a strange at first glance combination of numbers 1 and? indicates the width of the tire. Sometimes instead of an integer and a fraction, the width is indicated as a non-integer with a dot, for example 26x1.75.
Often there is a marking of three numbers: 20x1.75x2 or 28x1 ⅝x1 ¾. In this case, the first number is the outer diameter, the second is the height, and the third is the width.
For bicycles made in France or some other European countries, a different marking is adopted. Type 650A means that the outer diameter of the tire is 650 millimeters, the letter A is its width. But such marking is now becoming less common, it has been replaced by a more accurate designation of diameter and width. Today it is customary to label bicycle tires as follows: 650-38С, where the first number is the outer diameter, the number after the hyphen indicates the width of the tire, and the letter (in this case, C) is the size indicating its inner diameter.
Wheel diameter measurement
In order to find out the diameter of the wheel, it is necessary to measure its radius with a tape measure. For measurement, the bike is mounted on a flat surface and, extending the flexible tape of the instrument a few centimeters, lower its lower edge to the ground or floor, after placing the elongated part as close as possible to the bushing axis.
To find out the full diameter of the wheel in millimeters, you need to multiply the result by 10, and then by 2.
You can determine the diameter of the wheel without roulette. For this it is necessary apply a coloring compound in the form of a bracket on the tire and turn the wheel one revolution. The length of the line from 1 point to the second is divided by 𝝿 (3.14) and, if necessary, converted to inches, dividing the result by 2.54.
How to choose?
In order to choose the right tire, it is necessary to focus, of course, on the marking and compare the data with the signs indicated on the old tire. Parameter compatibility should be maximized. But, as practice shows, first of all, you need to compare the tire width with the inner width of the rim.
Two very important parameters for a cyclist depend on the ratio of these two quantities: knurling and grip. The tire, which is wide relative to the inner size of the rim, allows you to better control the bicycle on bends; grip on the surface of this tire is better. But unfortunately, the ride of a bike with such a width is worse.
The optimal ratio between the tire width and the inner rim size is 1: 1.5 or 1: 2, and all values are in the range from 1.5 to 2.
Tires from 18 to 25 mm wide are suitable for a road bike with a rim width of 13 mm, and in the case of 15 mm it is better to opt for a tire marked 23–32 mm.
For light cross-country models with a rim width of 17 mm, tires 25-37 mm wide are needed, and for heavy crosses with a rim of 1 mm, instances with a width of 28–44 mm are suitable.
Models designed for mountain bike rides with a rim of 19 mm are suitable for tires with a width of at least 28-60 mm. For bicycles used in cycling and light extreme sports, with a rim size of 20 mm, tires with a width of 28 to 47 mm are produced. And with a rim width of 21 mm, the tire width will be in the range of 35-50 mm.
For bicycles used in extreme sports with a rim of 23 mm, the width of the tires should be between 40-50 mm, for a rim of 25 mm, a width of 44 to 57 mm is suitable, and for the largest rim of 32 mm, tires with a width of not less than 75 mm.
It must be remembered that too narrow a tire greatly increases the risk of puncture and rim damage.
Too wide a tire will reduce handling at low speed, even if it is slightly deflated. When making a turn, an excessively wide tire can cause it to break off the rim. Besides, the wear of such tires is much faster than a properly selected option.
The presence of spikes affects the choice of tire width. Studded tires that are too wide, coupled with a narrow rim, are not the best combination for good traction, since when turning, the studs located in the side will practically not come into contact with the surface.
The reverse situation will develop with a narrow tire and a wide rim.
When making a turn, the spikes will be in full contact with the surface, but insufficient width and slope will cause the bike to ride on the right or left side, depending on the turn, on the side.
About what sizes of bicycle tires are, see the next video.
