Some things sound boring and hard to remember, but you need to know them. Especially for car enthusiasts. Especially those who consider themselves experts and have their own opinion on any occasion. The devil is in the details, and this article is about one such detail.
Tire does not have a radius
A lot of people don't even understand what I'm getting at. “Well, radius, so what? I have wheels 195-65R15, radius 15, everything is written, what are you trying to be smart about ?! Here's what I'm thinking. R15 has nothing to do with radius. Neither R nor 15.
Now on the Internet you can find a lot of information, only such trifles as the marking of car tires are not among the most popular. We better discuss engine power or the number of "buns" in the cabin, right? And we will leave the choice of wheels to the manager in the store. Or ask a friend. He definitely knows! He already has a third car!
In fact, it won’t hurt to understand these boring numbers even just for general development. Moreover, this will help save money and influence the behavior of the car, but more on that later. So far - a pure educational program, so that later it would be possible to understand each other well.
So, 195/65R15. Classic case. Squat down next to your car. The first number is the width of the running part of the tire, roughly speaking, the width of the tread. Expressed in millimeters. That is 195 mm. is the width of your wheel. With the understanding of this number, most of the problems are not.
Through a fraction, 65 is the value of the profile. Expressed as a percentage of the width. Not in millimeters! The profile is the part of the tire that sticks out above the rim. Sidewall. That is, the height of this sidewall will be 195x65% = 125.75 mm. Not 65mm. And not something else. Moreover, from this scheme it clearly follows that the height of 65% with a width of 195 will be one, and if the tire is marked (conditionally) 225 / 65R15, it will be completely different! 225x65% = 146.25 mm. Although the numbers 65 are the same!
R stands for the radial construction of the tire, and more specifically, the way the metal cord is laid inside it. The tire design used to be bias-ply, but that was a long time ago. Now you almost never see “diagonal” tires, they are all completely radial, and the letter R will not tell anyone anything new, it will only cause disputes about the notorious radius ...
And finally, the number 15. This is the diameter. The diameter of the landing part of the tire, the inner diameter, the part that is in contact with the disc. Expressed in inches. 1 inch \u003d 2.54 cm. That is, 15x2.54 \u003d 38.1 cm This is also the outer diameter of the disk, if someone has not guessed ...
What tires can and can't be fitted?
And then the fun begins. We can play with these numbers if we want to put other tires (rims) on the car. Ideally, the main thing is that the overall diameter does not differ, or differs slightly. Example.
The wheel 195 / 65R15 has the following overall diameter: 38.1 cm - inside, plus 125.75 mm x2 \u003d 251.5 mm (there is a profile both above and below). Converting to centimeters for simplicity, we get 38.1 cm + 25.15 cm = 63.25 cm. That's how! This is the total wheel diameter.
Now, if you want to put other wheels on, the owner of the car must understand the following: automakers understand this figure in the same way as we do. Given the diameter of the wheel, the suspension, brake system and body are designed. Therefore, for the same car model (for example, for the Volkswagen Polo sedan), three wheel sizes are officially allowed. The simplest version is content with 175/70R14 (overall diameter 60.06 cm), 185/60R15 (60.3 cm) and 195/55R15 (59.55 cm).
It turns out that the “wheel by 14” is MORE, albeit slightly, than the wheel by 15 in the case of 195/55. This is to the question raised above, about how to put more wheels for the winter ... You need to carefully calculate everything. Will a larger diameter number also mean a larger wheel size overall? Not always.
It is always better to purchase complete wheels right away, but if you suddenly had to start selecting tires according to disks, then don’t worry, now we will study all the features of this process so that even an inexperienced person can handle it.
Main parameters and their designation
First you need to familiarize yourself with the main parameters and their designation. The wheel diameter is indicated by the symbol "D" and is considered the most significant characteristic. It is very important to follow the dimensions recommended by the manufacturer. The increased diameter will contribute to the distortion of the speedometer readings. It is also possible for the wheel to rub over the elements of the body and chassis.
The diameter of the rims is designated "dd", but their width (the distance between the inner edges of the rim) is "Wd", and in the marking it is usually indicated in inches. Height also matters, this characteristic has the code "dt". Low profile tires wear out faster and are not suitable for all roads. If the condition of the road surface is not ideal, then it is better not to buy such tires, since in this case the load on the suspension increases, and there is a possibility of disk deformation. In addition, they are noisier.
"Wt" - tire width. For driving on a dry track, wide tires are better, as this shortens the braking distance. For urban conditions and slippery roads, it is recommended to use narrow tires.
Before talking directly about the selection of tires by disks, it is necessary to disassemble a little in the marking of one and the other. Let's start with disks. The marking may be embossed anywhere except on the inner surface facing the rim. To make it easier to understand, consider the decryption using a specific example.
Let's say you found the following code "6.5JJx13FH6x98ET20d62.1". The first is the width of the disk and it is indicated in inches, in our case it is 5.5. to convert this value to millimeters, multiply it by 25.4. This is followed by a Latin letter (P, D, B, K, J) or a combination of them (JJ, JK). This symbol characterizes the shape of the profile contour, the height of the shelves, their angle of inclination and the radius of curvature. "JJ" indicates that the car is full drive.
If you see the symbol “x” behind the letter designations, then this means that the disc has a one-piece design, but collapsible copies in the marking contain the “-” sign. Next, the diameter of the disks is indicated, followed by the hump index. This is a value indicating the annular protrusions along the rims. They have a very important function - fixing tubeless tires during turns. A simple hump is denoted by a single letter "H", flat, as in our case, "FH", and an asymmetric one - "AH". There are designs in which there are no humps.
Next, the value that you need to pay special attention to when choosing tires for disks is indicated, this is the location of the mounting holes, in our case “6x98”. This suggests that there are 6 of them, and the diameter of the circle is 98 mm. The number of holes ranges from 4 to 6, and the circumference can range from 98 to 137.9 mm. The following indicates the distance between the plane of attachment of the disk to the hub and its vertical axis. This parameter is called disc overhang and is denoted by a combination of letters "ET". The number following them indicates the offset value in millimeters, in our case it is 20 mm.
The overhang can be positive, zero, or negative. Suspension and steering are adjusted depending on this parameter. The last in the marking indicates the diameter of the mounting hole. For passenger cars, this value is in the range from 50 to 70 mm. Quite often, the maximum load, the date of manufacture and the method of production are also specified. Discs are available forged, cast and stamped.
Tire marking
If you decide to start selecting tires according to the width of the disks, then you definitely need to be able to decipher the rubber markings. After all, this code contains all the necessary information. You can find it on the side surface of the tire. However, it also indicates a lot of other information about rubber, starting from the country of the manufacturer, model and ending with the purpose and type. This information, of course, is of great importance, as it affects the quality of the product, but if we are talking about the selection of rubber for certain disks, then they do not play a decisive role.
But the most important information is contained in the code, called the standard size. To make it as clear as possible, consider the decryption using a specific example. Let's say you found the following code "225/50 R14" on the side of the rubber. The first number indicates the width of the profile in millimeters. Moreover, measurements are made taking into account the sidewalls. Next comes the height value, expressed as a percentage relative to the width. With us it is 50%, which means that in order to come to the size in millimeters, you need 225x50%, it turns out 112.5 mm.
The next symbol gives information about the construction of the cord. "R" means that the tire has a radial ply. And the number following it expresses the mounting size of the rim, it is indicated in inches. In fact, this is the most important information that is needed when selecting tires by size. The marking also contains a column with speed indices, as well as loads. There are many tables on the Internet in which these alphanumeric designations are translated into specific values \u200b\u200bof loads and speeds.
What will help you choose the right tires?
The choice of rubber is a very responsible task, because if you put tires that do not meet its technical characteristics on a car, then problems cannot be avoided. These may be incorrect speedometer readings, and even wheel arches touching the rubber. How to find out what tires are needed if, for example, you bought a used car and faced with their replacement for the first time?
There are several ways to do this. The easiest way is to look in the book for the operation of the machine, in it you will surely find the necessary data. Sometimes we don’t have such an opportunity, in this case you can look under the glove compartment lid, where there is a special table with the necessary information. True, there are cars where such a table is not provided. What to do?
Don't be discouraged, you can always go to specialized sites that sell tires, and by filling out a plate (year, brand and other information about the vehicle), you will receive detailed information on rubber that is ideal for your car. If you decide to put tires of a different size on the car, then the tire calculator will help you track the change in the linear dimensions of the rubber and the speedometer reading.
How to match tires and rims?
But there are cases, again, they are more often associated with supported cars, when it is necessary to select tires according to the size of the disks, because these two components should correspond to each other as much as possible. Then simple rules will help. For example, the width of the rubber profile should be 25–30% larger than the size of the rim. So, for example, if the width of the disk is 5.5 inches, then, adding 30% to this value, we get 7.15 inches or 185 mm. It is important that these two parts match in their central holes. But if for some reason this does not work out, then a special adjusting ring will come to the rescue. Its outer diameter corresponds to the disc hole, and its inner diameter corresponds to the hub.
But this is not all the features of selecting tires for. It is also necessary that the tires strictly correspond to the diameter of the circumference of the disc mount centers. A maximum run-out of 2 mm is allowed. In this case, special bolts with eccentrics are used for fixing. But it is best if these parameters match 100%.
In order not to miscalculate exactly with the choice, you can refer to special tables for selecting tires for disks, where their sizes and correspondence are indicated.
There is also such a thing as maximum load. Usually they rarely pay attention to it, since disk manufacturers make their products with a good margin of safety. However, if you decide to experiment and, for example, install wheels from a sedan on a jeep, then be sure to find out this characteristic. It is quite possible that the disk will not withstand such a load, and the first hole or hillock will lead to very sad consequences.
Each car owner is faced with the choice of tires for the car. This may be a change in seasonality (summer, winter), a scheduled replacement or a tire change in order to improve any performance. Before proceeding with the choice, each owner must know how to choose the right tires for his car - this means not only understanding what characteristics are required, but also such parameters as the outer diameter of the tire and suitable wheel sizes (recommended for installation).
Diameter and dimensions
The modern market offers a huge number of tires of different sizes for any conditions. But each car has its own allowable tire diameter sizes. To find out which one is suitable for a car, you need to use the instruction manual for the car (if factory tires are installed) or use the marking that is applied to the tires.
Marking
It is applied to each tire, and contains all the information. An example is 205/55/R16 94HXL:
- 205 - the indicator indicates the width of the tire in millimeters;
- 55 - the ratio of height to width. In the considered variant, the value is equal to 55%. If the value is missing, then the value is 80-82% (used on light commercial vehicles).
Important: if the car owner decides to install wider tires (let's say 215/55), then this will mean that the rubber will be higher.
- R - means that the tire is a radial type. There is a diagonal design (indicated when marking - D), which is used quite rarely in the modern world. It is explained by the fact that the characteristics during operation are lower than that of the radial one.
- 16 - inner diameter of the wheel (in inches). If you need to convert the value to centimeters, then it is worth remembering that 1 inch is equal to 2.54 centimeters, and is calculated by multiplication.
Attention: the value is used to select disks. For disks, 16 is the outer (landing) diameter. The radius of the entire wheel is another value.
- 94 - the possible load on one wheel is about 670 kg. The value indicates the possible load.
- H is the maximum speed that can be developed on tires (speed index).
- XL - the tire is made with a reinforced carcass, and has a margin of safety in case of "overload" of the car.
There are many markings that can give additional information about the tire, up to the number of the inspector at the manufacturing plant. You can decipher the values in full, but the main parameters that will help give information when selecting are described above.
Size and wheels
To make the correct selection of the diameter and size of tires, you must contact a specialist, or refer to the manufacturer's recommendations to find out the appropriate values for a particular machine. Among all the diameters of winter tires and summer tires, the most popular can be distinguished: R19; R18; R17; R16; R15; R14.
Important: it is necessary to follow the recommendations - if the size does not match, then it is possible that the tire, when driving, will touch the body, or, due to a shift in the center of gravity, some indicators will deteriorate, possibly rapid rubber wear, when installing tires with the wrong offset.
When you need to choose wheels for a certain tire size, you can use the table:
| Disc width | Minimum tire width | Suitable tire width | Maximum tire dimensions | |
| 5 | 155 | 165 | 175 | 185 |
| 5.5 | 165 | 175 | 185 | 195 |
| 6.0 | 175 | 185 | 195 | 205 |
| 6.5 | 185 | 195 | 205 | 215 |
| 7.0 | 195 | 205 | 215 | 225 |
| 7.5 | 205 | 215 | 225 | 235 |
| 8.0 | 215 | 225 | 235 | 245 |
| 8.5 | 225 | 235 | 245 | 255 |
| 9.0 | 235 | 245 | 255 | 265 |
| 9.5 | 245 | 255 | 265 | 275 |
| 10.0 | 255 | 265 | 275 | 285 |
| 10.5 | 265 | 275 | 285 | 295 |
| 11.0 | 275 | 285 | 295 | 305 |
| 11.5 | 285 | 295 | 305 | 315 |
| 12.0 | 295 | 305 | 315 | 325 |
| 12.5 | 305 | 315 | 325 | 335 |
It is worth noting that not all selection values \u200b\u200bare indicated in the table - there are wheels from 3 inches or more, but everything directly depends on the radius of the wheel that will be selected for a particular car. Therefore, it is necessary to rely primarily on the recommendations of the car manufacturer, or on the comments of a specialist.
Resizing
Some car owners specifically change the radius of the wheels, and such changes are divided into several categories:
- Increase in width - it is permissible to increase this indicator by no more than 24 mm, but only while maintaining the same height. Otherwise, the wheel will rub against the body, which will quickly render it unusable. An example would be an R15 tire diameter with a dimension of 185/65. After the increase, the characteristics will be 195/65 (24mm is the maximum expansion value, the average is 12). After that, the stopping distance will decrease, and the car will start to go a little softer, but the price of buying new tires will increase.
- Height - the installation will slightly increase the patency, but it is impossible to increase the indicator much. This will lead to the rapid erasure of tires on the car body.
- Wheel offset - some car owners seek to increase the width of the disk, and it turns out that the wheel turns out to be slightly protruding from the arch. Such a change is detrimental to the car, and will quickly lead to failure of the suspension. The optimal wheel offset is regulated by the manufacturer, and it is not recommended to change it.
- The outer diameter of the disc - car owners sometimes seek to increase the diameter of the disc, and use low-profile rubber as tires. For example, with a tire diameter R16 and size 195/60, it is suitable for replacing a wheel with characteristics 185/65 and 15 radius - in this case, you will have to sacrifice driving performance and smoothness. There are cases when a decrease in diameter leads to an improvement in the running characteristics of the machine, namely, an increase in the softness of the suspension. But there will be disadvantages in this - at high speeds, the car may lose directional stability.
The bottom line is the following: when choosing new rims and tires, the best solution would be a selection based on factory recommendations. To change the tire parameters, you need to clearly imagine what this can threaten during the operation of the car.
Installing and choosing modified tires on your own, without consulting a specialist, is not recommended, and can lead to failure of the entire car.
The labeling of tires manufactured in America is very different from European designations. Therefore, drivers constantly have to convert inches to millimeters or centimeters. Only by making such calculations, you can choose the right wheel for your car.
29 inches
The Russian SUV is produced with wheels, the diameter of which is slightly smaller than that of a conventional SUV. The standard size of foreign cars is 29 inches or 235/75R15.
The domestic SUV (Niva) is equipped with 175 / 80R15 wheels at the factory. On such tires, the car quickly burrows into the mud, hardly moves along our impassability.
To fix this situation, you need to install 29 inch tires. It will increase the clearance by 25 mm. If you install tires 31 inches, the ground clearance will increase by 50 mm. To install such wheels, you only need to change the wheel arches. It will be necessary to increase their dimensions.
Inch system
Most Jeeps use tires marked 31x10.5R15.
31 here refers to the inch diameter of the wheel. One inch, as you know, corresponds to two and a half centimeters, and to be completely accurate, then 2.54 cm. In other words, after the transfer, D will become 78.7 cm.
Such a marking is quite in demand, as it is convenient, since it shows the size of the wheel with the disk parameters already taken into account.
The wheel diameter 31x10.5R15 is almost equal in size to the tire with the designation 31x10.5R16. The only difference will be a reduction in the tire profile by 2.5 cm.
10.5 - tire width in inches. But this value is not entirely accurate, since when converted from inches to traditional centimeters, you get 26.5 cm.
However, when measuring this value with a conventional ruler, the value will fluctuate within 23 cm. Only if the tire has a width index of 12.5, it will be possible to talk about a width of 26.5 cm.
You should always remember this nuance if you decide to install the maximum tire size in the arch of an SUV.
Metric system
This measurement system is much more difficult to use. Take rubber marked 265-75-15.
265 mm - tire width. Just like in the inch system, its actual width will be approximately 230-235 mm.
75 - profile height in millimeters. To get the true value, you need to take 75% of 265 mm. It will be 198.75 mm. This number is then multiplied by two. This is because the total wheel diameter is D of the rim plus twice the profile height.
In our case, it is equal to 15 inches. As a result, after the calculations, we get a D disk of 381 mm. Total wheel D: 397.5 + 381 = 778 mm or 77.8 centimeters.
R15 - radial rubber. Disc diameter is in inches. Always a surprise. Why is the inch designation left in the metric system.
If you look closely at these two systems, you will notice a slight difference, about 1.1 centimeters. It does not affect the design and installation of the wheels in any way.
Today on the Internet for the correct calculation of tire size, a large number of various calculators are offered. All of them work completely free of charge and make it much easier to find the right tire size.
You can get acquainted with the rating of summer tires 2019 on our website
We have compiled a table of the most common sizes, perhaps it will help you quickly find the right wheel size.
| Notation | inches |
| 235/65R16 | 28,0 |
| 235/75R15 | 28,9 |
| 225/75R16 | 29,3 |
| 245/70R16 | 29,5 |
| 285/60R16 | 29,5 |
| 225/85R15 | 30,1 |
| 245/75R16 | 30,5 |
| 265/65R17 | 30,6 |
| 265/70R16 | 30,6 |
| 305/60R17 | 31,4 |
| 265/70R17 | 31,6 |
| 265/75R16 | 31,6 |
| 235/85R16 | 31,7 |
| 285/70R16 | 31,7 |
| 285/70R17 | 32,7 |
| 285/75R16 | 32,8 |
| 305/70R16 | 32,8 |
| 255/85R16 | 33,1 |
| 305/75R16 | 34,0 |
Acquainted with
