Sizes of bicycle tires: what are they and how to choose the right option?

There are many reasons people buy a bike. Regardless of the purpose of this vehicle, its most important element is the tires, which often have to be changed. What they are and how to choose them correctly, you can find out from this article.

The dimensions of the wheels (rims) are the determining factor, because they determine the purpose for which the bike is suitable. Previously, when selecting bicycle tires, they were guided only by the outer size of the circle, but over time, a fairly large number of manufacturers appeared in the world, as a result of which confusion arose. In order to make it easier to navigate the types of tires and to select them correctly for your bicycles, unified system of standards.

It was developed by the international organization for standardization ISO, formerly known as ETRO. This system takes into account the width of the tire, the inner and outer rim diameters and the height.

Children's bicycles, balance bikes, scooters and some foldable designs typically have an outer rim diameter of 12 to 24 inches. For adult models, this parameter is in the range of 26-28 inches.

The inner rim diameter, or, as it is also called, the landing diameter, is the most important parameter for a tire, since it must match the inner width of the bicycle rim.

The inner tire size, according to ISO standards, 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 the parameters of the tire are indicated in accordance with the produced bike models and their purpose.

For two-wheeled vehicles produced in France and in some other European countries, there is its own correspondence table, in which the designations of the inner and outer diameters, width and height have a slightly different look.

Tire markings are almost always located on the side.

Most often, dimensions are indicated in millimeters. A two-number marking such as 35-559 or 37-630 denotes the width and inner diameter (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 such as 622x19 indicates the inner diameter in millimeters and the outer size of the part in inches.

Tires can also be labeled with numbers in inches only. The form 24x1 ⅛ means that the number 24 is the outer diameter, and a strange at first glance combination of the 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 number with a dot, for example, 26x1.75.

Often there are markings 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 manufactured in France or some other European countries, different markings are adopted. Type 650A means that the outer diameter of the tire is 650 millimeters, the letter A is its width. But such markings are now less common; they have been replaced by a more accurate designation of the diameter and width. Today, it is customary to mark bicycle tires as follows: 650-38C, 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, it is C) is the size indicating its inner diameter.

In order to find out the diameter of a wheel, you need to measure its radius using a tape measure. To measure, the bicycle is placed on a flat surface and, having extended the flexible tool belt a few centimeters, its lower edge is lowered to the ground or floor, after placing the elongated part as close as possible to the hub axle.

To find out the full diameter of the wheel in millimeters, you need to multiply the result obtained by 10, and then by 2.

You can determine the diameter of the wheel without a tape measure. This requires apply a staple paint to the tire and turn the wheel one turn. The length of the line from 1 point to the second is divided by? (3.14) and, if necessary, converted to inches, dividing the result by 2.54.

In order to choose the right new tire, you must, of course, be guided by the markings and compare the data with the designations indicated on the old tire. Parameter compatibility should be maximized. But, as practice shows, first of all, you need to compare the width of the tire with the inner width of the rim.

Two very important parameters for a cyclist depend on the ratio of these two values: roll and grip. The tire, which is wide relative to the inner size of the rim, allows better control of the bike when cornering, the grip of such a tire is better. But unfortunately, the roll on a bike with this width is worse.

For a road bike with a rim width of 13 mm, tires from 18 to 25 mm in width are suitable, and in the case of 15 mm, it is better to opt for a tire with a marking of 23-32 mm.

Light XC models with 17mm rims require 25-37mm wide tires, and heavy 1mm cross-country models require 28-44mm tires.

For mountain bike models with a 19 mm rim, tires with a minimum width of 28–60 mm are suitable. For bicycles used in cycling and light extreme sports, in which the rim size is 20 mm, tires are produced with a width of 28 to 47 mm. 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 23 mm rim, the tire width should be in the range of 40-50 mm, for a 25 mm rim, a width of 44 to 57 mm is suitable, and for the largest 32 mm rim, tires with a width of not less than 75 mm.

It must be remembered that A tire that is too narrow will greatly increase the risk of puncture and rim damage.

A tire that is too wide will reduce low speed handling, even if it is slightly deflated. When cornering, an excessively wide tire can cause it to come off the rim. Besides, the wear of such tires occurs much faster than the correctly selected option.

The presence of studs affects the choice of tire width. Too wide studded rubber coupled with a narrow rim is not the best combination for good grip, since when cornering, the studs located in the side section will practically not contact the surface.

The opposite situation will develop with a narrow tire and a wide rim.

For information on the sizes of bicycle tires, see the next video.