How to choose a tire size for a car

How to choose the right tires for your car

We have already figured out how to choose the right wheels for a car. Now our task is to select tires. There are probably as many markings on the sidewall of tires as there are parameters on the rim, but in general choosing a tire is a little easier. Let's find out what numbers like “185/70 R14 88H” mean and how to deal with them.

You need to choose the right tire for a wheel with the specified parameters or for a specific car.

When choosing tires, you need to consider the following parameters:

• seasonality;
• tread type;
• type of tire design - tubed or tubeless;
• type of cord construction;
• mounting (or landing) diameter;
• tire width;
• profile height;
• load index;
• speed index.

As in the case of choosing wheels, let’s make a reservation right away: if at this stage you no longer want to understand numbers and indices, you can simply use the tire calculator of any large online store or online service, where you can instantly select tires by indicating the model of your car or characteristics of existing disks.

However, if you continue reading, then it has already become clear to you that in fact the above list of parameters is quickly reduced to two or three points, since most of them are obvious or subjective characteristics. Let's go in order.

Seasonality is an obvious parameter: at the time of choosing tires, you understand perfectly well whether you need winter or summer tires. The issue of choosing so-called “all-season” tires and its applicability in conditions of year-round use is a topic for a separate discussion, as is the choice of mud or “universal” tires. Here it is only worth saying that winter tires must be marked with the “snowflake” icon or the letters “M+S” or “MS”.

In general, the tread pattern can be symmetrical or asymmetrical, as well as directional or non-directional. Symmetrical non-directional tread is the simplest basic type of tread: these tires are the most common and inexpensive. The directionality of the tread primarily increases its ability to effectively drain water from the contact patch - this reduces the risk of aquaplaning . Well, the asymmetrical tread pattern is designed to combine good drainage and directional stability. The issue of choosing a projector pattern also deserves a separate discussion.

By design, tires are designed for use with or without a tube. However, in modern conditions, the question of choosing a tire design is almost predetermined: almost all modern passenger tires are tubeless. Such tires are marked with the inscription “Tubeless” (which means “tubeless”) or “TL”.

The type of cord construction – the strength part of the tire, its “skeleton” – is also a characteristic that does not require much attention when choosing modern tires: almost all of them today are radial. This fact is indicated by the very letter “R” in the tire marking: for example, the mark “185/70 R 14 88 H” means that this is a radial tire with a 14-inch bore diameter, and not a 14-inch “radius,” as is often mistakenly said consider.

This is also a simple parameter if you already have wheels for which you are choosing tires: the seat diameter of the tire must match the diameter of the wheel. If you choose wheels along with tires, you need to check in the instruction manual which diameter wheels are acceptable for use on your model, and only then select tires of the same size for them.

Tire width is the first digital index reflected in the tire marking. It is indicated in millimeters: the 185/70 R 14 tire has a width of 185 millimeters. This is perhaps the first parameter on our list, which can vary when choosing a tire for a particular wheel or car.

The point here is that the rim can also have different widths, and the tire must fit correctly on the rim. A tire that is too narrow will sit “like a house” on the rim, which is unacceptable due to the high risk of spontaneous dismounting, and a tire that is too wide will “mushroom”, which is also unacceptable. Some tuning trends like stance consider the “house” landing to be beautiful and make it a separate style element , but from the point of view of civilian use it is not justified and incorrect.

Each car model has several options for wheel diameter and tire size suitable for use. All these options, recommended by the manufacturer, are listed in the car's operating manual: it is from this data that you should choose. In turn, a rim of a certain width has several acceptable tire options. Here the choice should be made depending on the desired characteristics.

Firstly, wider tires usually provide a larger contact patch with the road and, accordingly, better grip. Secondly, given the same diameter, tires with a larger width have a smaller profile - we’ll talk about it a little lower. Thirdly, wider tires have more weight, which will slightly affect the car's dynamics and fuel consumption. Well, fourthly, as the width of the tires increases, their tendency to hydroplaning . In addition, tires of different widths have different final costs - as a rule, you will have to pay a few extra hundred rubles for additional millimeters. Thus, the width of the tires must be selected taking into account the range allowed by the manufacturer and the desired characteristics.

The profile height, or series, is the second index reflected in the tire marking. It is indicated as a percentage of the tire width: that is, it is the ratio of the profile height to the width as a percentage. For example, a 185/70 R 14 88 H tire has a profile height of 70% of its width. It’s easy to calculate the height in millimeters: you need to multiply the width by the profile and divide by 100 - for our tires this figure is 129.5 millimeters.

The profile height affects the characteristics of the tire. First, the higher profile provides better comfort and puncture resistance. Lower profile tires, therefore, better transfer the road profile to the suspension and body, and are also more prone to damage when hit by defects in the road surface. Secondly, a lower profile provides better handling, and a higher one, on the contrary, provides greater “rollability” of the car. Thirdly, as mentioned above, given the same diameter, tires with a larger width have a smaller profile - this must be taken into account when choosing in accordance with the desired characteristics.

Load index is a parameter that reflects the maximum permissible load on a tire during operation. It is indicated by a digital index, indicated after the geometric parameters of the tire: for example, our conventional tire 185/70 R 14 88 H has a load index of 88. The decoding of the index can be found in the table provided by the tire manufacturer - in our case, the index 88 means a permissible load of 560 kilograms. When choosing tires, it is worth considering that the maximum permissible weight of the car, accordingly, should not exceed the maximum load multiplied by 4 - the number of tires on the car.

Speed ​​index is a parameter that reflects the maximum permissible speed at which the tire maintains its performance characteristics. This is a letter index, the decoding of which also needs to be clarified in the table provided by the manufacturer. Tires of the same diameter can have different speed indexes depending on other parameters - width, profile, rubber compound composition and, accordingly, price. If the parameter of the maximum permissible operating speed is important to you, then you need to choose tires in a high price category with the best consumer qualities.

How to choose tires

The choice of tires for your car depends on several criteria, the main of which are seasonality and the size of the rim on which the tire . Other important selection factors are maximum tire load , speed characteristics, wet and dry grip parameters, handling, comfort, aquaplaning and wear resistance .

Modern tires are one of the most technically complex products used in a modern car . More than 40 components and dozens of chemical elements, complex chemical processes and a sophisticated testing system have created an entire industry, one of the most labor- and knowledge-intensive. First of all, remember that all forces, directions, torques created by a middle-class car to the road and back are transmitted through 4 contact spots with a total area of ​​no more than 2 A4 sheets! In fact, the entire passenger tire industry, technology and marketing are aimed at understanding the processes that occur in these contact patches and translating them into the safe movement of your car. At the same time, of course, not forgetting the aesthetic side of the issue, an effective tire should look beautiful.

Let's figure it out in order.

There are three types of tread patterns for passenger cars.

The first is tires with a summer tread pattern (or road). The tread has many constituent elements that form longitudinal grooves and ribs. As a rule, there is no micropattern on them. Such tires are designed for asphalt concrete roads with dry and wet surfaces and are unsuitable for driving on country roads, especially when wet. Moreover, they are not suitable for snowy roads in any condition.

The second is tires with a universal tread pattern ( all-season ). The grooves between the constituent elements are quite wide in the longitudinal and transverse directions. The tread also has a micropattern - narrow (“knife”) slots. The universal pattern gives good traction on soft ground. Universal tires perform much better on winter roads than summer tires. However, on hard surfaces (asphalt concrete), the universal tread wears out 10-15% faster than the summer one.

The third is tires with a winter tread pattern, which is formed in separate blocks separated by wide grooves. The grooves account for 25-40% of the tread area. Winter tires have a wide range of tread types and shapes - from relatively smooth ones for universal use (for cleared winter roads) to rough ones with developed lugs designed for snowy roads with ice. Winter tires are often equipped with studs. However, recently, especially in large cities, winter tires that do not have studs , the so-called friction or simply “ Velcro ” tires, have become very popular. What to choose - spikes or Velcro ? Tire experts say: “The choice of tire type depends on the operating conditions.” Friction, studless tires behave more confidently on snowy roads and on asphalt, studded tires are good for icy surfaces, wet ice and porridge. But all “ spikes ,” regardless of the manufacturer, make a lot of noise and quickly wear out when driving on asphalt, so it is not recommended to install them ahead of time. The braking distance of a studded tire on asphalt compared to a non-studded tire increases by 5-7%, and on ice and sleet the braking distance of “studs” decreases by 20-30% compared to friction rubber .”

When choosing a tire size, you must choose the size that is allowed by the vehicle manufacturer. What is a tire size? The standard size determines its geometric dimensions: width, height and diameter of the tire. For example, the marking “ 205/65 R16 ” means the following:

215 – tire width in mm;

65 – height (profile) of the tire as a percentage of the width (215 * 0.65 = 140 mm);

R – the letter “R” indicates that the tire design is radial (if there is no letter “R”, then the design is diagonal);

16 is the diameter of the rim in inches on which this tire should be installed.

All permitted sizes are indicated in the vehicle's operating manual. Often the same information is duplicated on the gas filler flap or in the driver's doorway. If you install tires with a diameter larger than what is allowed by the manufacturer (the outer diameter of the wheel will be larger than the approved standard sizes), then the wheel will most likely cling to the wheel arches, which is very unsafe and leads to premature tire wear.

If you install lower-profile tires than allowed, the car will become excessively “hard” and the suspension will “kill” much faster.

If you install tires with a higher profile than permitted, the car's handling will significantly deteriorate. The handling will become “wobbly”, and at high speed there is a risk of the tire coming off the rim!

Low profile tires make driving sharper and sharper. It is easier for the driver to control the car at high speeds, especially when cornering, so this type of tire will be more preferable for active driving. At the same time, it is worth remembering the other side of the coin - a low rubber profile dampens all road irregularities worse, so the suspension will break much faster. If the roads in your area are “rich” with potholes, then you should think about choosing tires with a higher profile .

In contrast to low-profile tires, tires with a higher profile “swallow” road surface imperfections quite well, while extending the life of the car’s suspension and providing sufficient comfort for the driver. If you are not a fan of thrills, fast and active driving, then this choice will be preferable for you.

For summer, it is preferable to choose wider tires , as this increases the contact patch with the road surface and, as a result, improves the dynamic characteristics of the car (the larger the contact patch, the greater the potential acceleration, both positive - acceleration, and negative - braking). On the other hand, this choice will slightly increase fuel consumption - the larger the contact patch, the higher the rolling resistance. In addition, do not forget about overcoming puddles - the wider the tires, the lower the speed hydroplaning .

As you can see, choosing a tire size is a rather non-trivial task, for the optimal solution of which it is necessary to take into account many factors. However, for the average driver of a large metropolis, in most cases the optimal choice will be, paradoxically, the average size from a number of combinations offered by the car manufacturer. If you already have rims and you are not going to change them, then the problem of choosing the size of summer tires is reduced to a minimum, but you should definitely remember the advantages and disadvantages of such a choice.

3. Maximum tire load

permissible load index (or load capacity index, also called load factor) is a conditional parameter. Some tire manufacturers decipher it: the tire may have Max Load (maximum load) and a double figure in kilograms and British pounds.

Some models provide different loads on tires mounted on the front and rear axles. The load index is a number from 0 to 279 that corresponds to the load that the tire can withstand at maximum internal air pressure. There is a special table of load indexes , from which its maximum value is determined. For example, an index value of 105 corresponds to a maximum load of 925 kg.

4. Speed ​​characteristics

The maximum speed recommended by the tire manufacturer can be deciphered by the speed index , which is printed on the sidewall of the tire. However, this index not only and not so much limits the maximum speed limit of the vehicle on your tires . A vehicle's maximum speed is limited by road conditions, driver experience, and many other factors. For example: incorrect pressure (especially low) in tires radically levels this indicator. The speed index, perhaps, more indicates the stability of all the qualities and characteristics produced by your tire up to a given speed (naturally, at the correct, recommended pressure). In other words, the the speed index , the better, and the more effective the basic qualities of the tire (traction, comfort, wear resistance, aquaplaning resistance ) when driving at high speeds. Tires with a high speed index (they are 10-15% more expensive) are more suitable for active drivers.

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Tire markings

Do you want to choose a tire for your car, but are not well versed in tire labeling? It's not a problem! In this section, we will help you figure out what tire parameters are, what they mean, and which tire is suitable for your car.

Decoding tire markings.

195/65 R15 91 T XL

195 is the width of the tire in mm.

65 - Proportionality, i.e. ratio of profile height to width. In our case it is 65%. Simply put, with the same width, the larger this indicator, the higher the tire will be and vice versa. Usually this value is simply called “profile”.

Since the tire profile is a relative value, it is important to take into account when selecting tires that if instead of size 195/65 R15 you want to install tires with size 205/65 R15, then not only the width of the tire will increase, but also the height! Which is unacceptable in most cases! (except for cases when both of these standard sizes are indicated in the car’s operating book). You can calculate exact data on changes in external wheel dimensions in a special tire calculator.

If this ratio is not specified (for example, 185/R14C), then it is equal to 80-82% and the tire is called full-profile. Reinforced tires with this marking are usually used on minibuses and light trucks, where a large maximum load on the wheel is very important.

R stands for radial tire (in fact, almost all tires are made this way now).

Many people mistakenly believe that R- means radius of the tire, but this is precisely the radial design of the tire. There is also a diagonal design (denoted by the letter D), but recently it has practically not been produced, since its performance characteristics are noticeably worse.

15 — wheel (disk) diameter in inches. (It’s the diameter, not the radius! This is also a common mistake). This is the “fitting” diameter of the tire on the disk, i.e. This is the inner size of the tire or the outer size of the rim.

91 — load index. This is the level of maximum permissible load on one wheel. For passenger cars, it is usually done with a reserve and is not a decisive factor when choosing tires (in our case, ID - 91 - 670 kg). For minibuses and small trucks, this parameter is very important and must be observed.

Tire load index table:

T is the tire speed index. The larger it is, the higher the speed you can drive on a given tire (in our case IS - N - up to 210 km/h). Speaking about the tire speed index, I would like to note that with this parameter the tire manufacturer guarantees normal operation of the tire when the car is constantly moving at the specified speed for several hours.

Speed ​​index table:

American tire markings:

There are two different markings for American tires. The first is very similar to the European one, only the letters “P” (Passanger - for a passenger car) or “LT” (Light Truck) are placed in front of the standard size. For example: P 195/60 R 14 or LT 235/75 R15. And another tire marking, which is fundamentally different from the European one.

For example: 31×10.5 R15 (corresponds to European standard size 265/75 R15)

31 is the outer diameter of the tire in inches.
10.5 - tire width in inches.
R is a radial tire (older tire models had a diagonal design).
15 is the inner diameter of the tire in inches.

Generally speaking, apart from the unusual inches for us, the American tire markings are logical and more understandable, unlike the European ones, where the tire profile height is not constant and depends on the width of the tire. And here everything is simple with decoding: the first number of the standard size is the outer diameter, the second is the width, the third is the inner diameter.

Additional information indicated in the markings on the sidewall of the tire:

XL or Extra Load is a reinforced tire, the load index of which is 3 units higher than that of conventional tires of the same size. In other words, if a given tire has a load index of 91 marked XL or Extra Load, this means that with this index, the tire can withstand a maximum load of 670 kg instead of 615 kg (see table of tire load indexes).

M+S or tire marking M&S (Mud + Snow) - mud plus snow and means that the tires are all-season or winter. Many summer SUV tires will say M&S on them. However, these tires cannot be used in winter, because... winter tires have a completely different rubber composition and tread pattern, and the M&S badge indicates good cross-country ability of the tire.

All Season or AS all-season tires. Aw (Any Weather) - Any weather.

Pictogram * (snowflake) - tires are intended for use in harsh winter conditions. If there is no this marking on the sidewall of the tire, then this tire is intended for use only in summer conditions.

Aquatred, Aquacontact, Rain, Water, Aqua or pictogram (umbrella) are special rain tires.

Outside and Inside ; asymmetrical tires, i.e. It is important not to confuse which side is external and which internal. When installing, the inscription Outside should be on the outside of the car, and Inside should be on the inside.

RSC (RunFlat System Component) - RunFlat tires are tires on which you can continue driving a car at a speed of no more than 80 km/h with a COMPLETE loss of pressure in the tire (due to a puncture or cut). On these tires, depending on the manufacturer's recommendations, you can drive from 50 to 150 km. Different tire manufacturers use different designations for RSC technology. For example: Bridgestone RFT, Continental SSR, Goodyear RunOnFlat, Nokian Run Flat, Michelin ZP, etc.

Rotation or arrow, this marking on the sidewall of the tire indicates a directional tire. When installing a tire, you must strictly observe the direction of rotation of the wheel indicated by the arrow.

Tubeless is a tubeless tire. If this inscription is missing, the tire can only be used with a tube. Tube Type - means that this tire must be used only with a tube.

Max Pressure ; maximum permissible tire pressure. Max Load - maximum permissible load on each vehicle wheel, in kg.

Reinforced or the letters RF in the size (for example 195/70 R15RF) mean that this is a reinforced tire (6 layers). The letter C at the end of the size (for example 195/70 R15C) indicates a truck tire (8 plies).

Radial - this marking on the tire in the standard size means that it is a tire of radial design. Steel means that the tire has a metal cord in its construction.

Letter E (circled) - the tire meets the European requirements of ECE (Economic Commission for Europe). DOT (Department of Transportation - US Department of Transportation) - American quality standard.

Temperature A, B or C is the heat resistance of tires at high speeds on a test bench (A is the best indicator).

Traction A, B or C - the tire's ability to brake on a wet road surface.

Treadwear ; relative expected mileage compared to a specific US standard test.

TWI (Tread Wear Indiration) - indicators of tire tread wear indicators. The marking on the TWI wheel may also include an arrow. The indicators are located evenly in eight or six places around the entire circumference of the tire and indicate the minimum permissible tread depth. The wear indicator is made in the form of a protrusion with a height of 1.6 mm (the minimum tread size for light cars) and is located in the tread recess (usually in the drainage grooves).

DOT - Manufacturer's encoded address, tire size code, certificate, date of manufacture (week/year).

Selection of tires by car make

What size do you need? Select tires based on your car brand. Select the manufacturer, indicate the model, year and modification - get a list of suitable sizes.

Selecting the right tires - a smart robot works for you

How to choose tires for a car? It is necessary to take into account all standard sizes and recommendations of the machine manufacturer. It is advisable to try on the wheel to eliminate any last doubts.

Some sites offer tables where you need to do a little digging and then you can make a choice. Or oral assistance from an expert.

On the Samokhodoff website, the selection of tires by car make is easier!

We have automatic selection. If you are lost in the variety of products presented in the catalog and find it difficult to make an independent choice, this wonderful program will help. She will look through the catalog for you in a second and select exactly the tires that are required for your car.

A couple of clicks and you know your size

Once you have determined the car model, you need to narrow down the selection of tires. Select the tire manufacturer, season, diameter and additional parameters, such as runflat; Check all the necessary boxes. Now you have the most suitable options. With one click from the search result, you can go to the page of the corresponding product, read about it, and if you like it, order it.

Principles for selecting tires for Samokhodoff

When creating the selection program, we paid special attention to the following points:

1. Accuracy. Our algorithm is more competent and professional than some real services. There is no doubt about the result.
2. Professionalism. The program doesn't just sort through suitable sizes. She chooses products recommended by the car manufacturer.
3. Simplicity. We want any car owner who comes to the Samokhodoff website to be able to navigate as quickly and easily as possible.

If you decide to change your tire size to a non-standard one, then before using the selection of tires based on your car model, use a tire calculator, and also check whether the car’s warranty will expire after installing new wheels.