About the tire load index - how to choose and what it is. Tire load index Softness of rubber with different speed indexes

20.08.2019 13:15

The load index affects the weight that the tires can support, the comfort in the car and fuel consumption - that's why. Remember to pay attention to the tire load index when choosing new tires. The numbers are on the sidewall of the tire. And do not take this indicator lightly: car manufacturers do not in vain recommend using certain values ​​\u200b\u200band indices when choosing tires, this is of great importance.

What is load index

The index shows the maximum load in kg per tire at the maximum allowable speed. Speed ​​limits are also marked on the sidewall of the tire, next to the possible load capacity.

The higher the index, the heavier and stiffer the tire itself. Tires that are too hard interfere with comfort in the car, and their weight has a negative effect on suspension life and fuel consumption. Tires with a low index are light and soft, but wear out noticeably faster.

What are load indices

The operating instructions for the car will help determine the correct index - the manufacturer always indicates the permissible speed and load indices. The figure is formed based on the weight of the machine, its specifications, formulas, tests and other magical knowledge that is available only to engineers of a particular brand. Therefore, when choosing tires, stop at those indexes recommended by your car manufacturer: this way the ride will be more comfortable, and technical components such as suspension will last longer.

Load indices are indicated by numbers from 0 to 279. The standard load rating for a passenger car is from 62 to 126. For small small cars A-class tires with an index of 60 are used, each wheel can withstand up to 250 kg. Tires of B-class cars can withstand up to 315 kg, index 68. For representatives of the C-class, tires are marked with index 75 - this is 385 kg per tire. The tires of minivans and crossovers can withstand up to 545 kg, this is an index of 87. The wheels of SUVs and commercial vehicles are the most capable - they hold up to 775 kg, this is an index of 99.

Tire speed indices

If the load index is marked with numbers, then the speed readings are indicated in Latin letters and are located in the same place - on the sidewall of the tire. The index shows which top speed the tire can withstand. You can see all values ​​in the table:

Load index table

The index shows how much weight one wheel can support. Tires for passenger cars and off-road cars can withstand weight in the range of 250-1650 kg. You can find more information about the designation of the load index in the table:

How to calculate the tire load index for a car

The tire load must be multiplied by 4 - by the number of wheels. Subtract the weight of the vehicle and the weight of the passengers from the total. The remaining value will show the carrying capacity of the car - the weight of people and luggage that can be placed in the car without compromising safety. Otherwise, the tires will quickly become unusable, and on the road with pits and bumps they will be deformed.

It is not safe to drive at the maximum speed allowed by the tires with the maximum load on the rubber. The load index shows the maximum weight of the vehicle. We advise you not to approach the upper limit closely.

The main weight falls on the rear wheels: the main cargo is stored in the trunk, and passengers are placed in the rear seats. Take this into account when calculating the load.

Decryption

Pay attention to the indexes recommended by the car manufacturer - they should be indicated in the car's operating instructions. The greater the difference between the indexes between the tires you have selected and those recommended by the manufacturer, the less comfort you will feel while driving.

Tires for trucks mobiles marked with two load indexes. This is due to the fact that trucks often run on twin wheels. And in this case, the double designation shows the load when using one or two wheels. There are no other differences in the tire load index between cars and trucks.

Healthy

Based on materials from 110km.ru

When planning to buy tires for a car, knowledgeable motorists pay attention not only to the size, seasonality, manufacturer and its warranty, but also to the tire load index. Despite the fact that it can be specified in different ways, reading such an index is not difficult. So, having a minimum of knowledge, the owner of the vehicle can easily determine whether the tires are suitable for his car or not. Initially, it will be clear how the car will behave at maximum or, conversely, minimum load. In fact, this index is an indicator of the vehicle's carrying capacity. It determines what is the maximum number of kilograms that can fall on one wheel. Thus, a two- or three-digit number on the cord is no less significant than the dimension or, for example, the speed index.

What is the danger of ignoring the tire load index? What can result in the choice of rubber, where the load index is less than necessary? Despite the fact that exceeding this indicator by 10-30% is considered quite acceptable, a long run using such tires will result in increased tire wear. At the same time, the controllability of the car gradually deteriorates, and the car begins to behave in an unpredictable way during lane changes or braking. An unfavorable result may be overheating not only of the tires themselves, but also brake mechanisms. Agree, this is a lot to refuse to buy rubber, where the tire load index is lower than required.

But what if you buy tires where this indicator is higher than necessary? Buying tires with a margin is also a wrong decision, threatening big problems with the control of an unloaded machine. In addition, exceeding the recommended load index is fraught with the fact that:

The wheels will become much more “oak”, the suspension will wear out faster, and there will be obvious discomfort when driving;

Driving an unloaded car will require a lot of effort, and besides, the vehicle will slow down worse;

Tires with a high load index are often not designed for high speed driving.

It is also worth knowing that tires with a high load index are very demanding on rims. Therefore, having bought such rubber, it is often necessary to check the air pressure in the wheels and pay close attention to the quality of the discs and their evenness. Thus, when choosing tires, you should focus on an acceptable level of load, adhering to the principle of the "golden mean". It is worth knowing that the values ​​are indicated per wheel, and not total weight cars. However, the optimal indicator is not calculated by simply dividing the number indicated in the data sheet by the number of wheels. In most cases, the weight that falls on the rear and front axles of the car is not the same. Therefore, read the description of the vehicle, which will help determine which tire load index is sufficient for your car.

The table below shows the code interpretation of tire load indices

What are tire speed indexes?

1. The speed indicated in the index cannot be exceeded categorically, but the realities of domestic roads are such that it is highly desirable to subtract another 10-15% from this indicator.

2. The speed index is related to the type of tires (summer, winter or "all-weather"). When choosing tires for the cold season, you should pay attention to tires with an H index or possibly more.

3. Be sure to take into account the following pattern: the higher the index, the softer rubber and better grip on the road, but at the same time, rubber wear is greater.

4. If you plan to use tires with different speed ratings, put the hardest rubber on the drive axle to ensure even tire wear.

5. There is a lot from the tire tread. international standards an equal load factor is determined for passenger cars, however, the speed index for identical tires can vary from 180 to 240 km / h. At the same time, this indicator does not depend in any way on the manufacturer or on the year of manufacture of the vehicle.

Tire Speed ​​Index Table

Tire load index- a conditional numerical designation that shows what mass load the tire can withstand in long-term operation. This information is necessary in order to choose the right tire, and thereby ensure a safe and comfortable ride by car. To decipher the tire load index, a table is used, which shows the numerical designations of the index and the normal values ​​\u200b\u200bof the mass that corresponds to them. Next, we will give you such a table, as well as give information about speed index, which is also important when choosing a tire. You can find the rest of the information about the designations available on tires.

Load value (MAX LOAD) and tire pressure

Determination of the load index

First of all, it must be remembered that the numerical values ​​\u200b\u200bof the load index given on the tires are conditional! That is, these numbers do not mean the absolute maximum weight for which the tire is designed. As the load index increases, the maximum allowable weight of the machine for which it is designed also increases.

However, in the application plan, many drivers when buying new rubber interested in a simple question - which tire load index to choose in one case or another? It is easy to answer it. There are two options. The first is to ask for the relevant information in the manual for your car or in the reference literature. Many automakers directly indicate the information that a particular model needs a tire with such and such a load index (the same applies to the speed index, although selection is easier there, but more on that later). The second option is to do the calculations yourself.

Load index for cars can be calculated based on the empty weight of the machine with the maximum load. That is, to the mass of the equipped car (with a fully refueled fuel tank, process fluids, repair kit, spare wheel, etc.) the mass of the maximum number of people placed in it is added (for cars usually it is 5), as well as some mass of additional cargo (it all depends on the specific car, for small cars it can be 100 ... 200 kg, and for SUVs - over 500 kg). Approximate index value for different types cars:

• 60 - load up to 250 kg - for A-class cars;
• 68 - up to 315 kg per wheel - for B-class representatives;
• 75 - 387 kg per wheel - for C-class cars;
• 87 - 545 kg load - for minivans and crossovers;
• 99 - 775 kg - for SUVs and light commercial vehicles.

Further, the resulting maximum mass must be divided by four (for traditional machines with four wheels). And after that add 35...40% of the stock. Having carried out such simple calculations, you will get the absolute value in kilograms that the tire must withstand. The final stage is the choice of a symbol for the load index of the machine according to the table. Please note that you must select the coefficient corresponding to the nearest HIGHEST absolute value.

In order not to bother with the calculations of the load index required for the tires of your car, it is possible to quickly calculate everything on a special calculator. It will immediately give you the required number.

Often, for specific models of cars in stores, there are already several options, from which you can choose the most suitable for you in terms of quality, price and manufacturer.

Keep stock up to date for rear wheels especially if you often carry heavy loads. However, do not be zealous and choose tires with an index that is too high. The fact is that the more load the tire is designed for, the more rubber is used for its manufacture. Accordingly, such a tire will be heavier, and hence arises three negative factors.

The first is that the engine will be forced to expend additional effort (and hence fuel!) To rotate the heavy wheel. The second is that a heavy tire will be very stiff, so it will be uncomfortable to ride on it. The third - with heavy tires, the suspension of the car experiences an additional load, which means that its normal operation period is reduced.

Next, we give you the promised table that will help you decipher the tire load index (here you will find tire values ​​\u200b\u200bfor all types of cars - cars, SUVs, trucks, and so on). For cars and SUVs, tires with an index value from 60 to 125 are used (respectively, from “A” class cars to heavy SUVs).

The designations of the load index and tire speed on the lateral surface of the rubber are located nearby. And this is no accident, because they are interconnected. Unlike the load, the speed index has a letter designation in Latin letters (from A to Z). For example, you can find the values ​​92S or 88T on the tire, which will just be the combined designation of the two mentioned indices.

The speed index is specially placed next to the load index. This information gives an idea. what kind of load can the tire withstand at its maximum speed.

Deciphering the tire speed index is very simple. The closer the letter is to the end of the alphabet, the more speed the tire is designed for. The only exception is the letter H, located between U and V. So, we give you a similar table with which you can clarify what maximum speed this or that tire is designed for.

How to choose load and speed indices

Deciphering load and speed indices

European regulations ECE-R54 require all tire manufacturers to put load and speed index values ​​on them. In this case, the load index is usually indicated for single installation wheels on an axle on one side. If the rubber can be used for a double installation, then two values ​​\u200b\u200bare indicated through a dash. For example, 102/100R. The first number is for a single installation, the second is for a dual installation. Tires have such a double designation Commercial class, which, in accordance with the same rules, can be installed not only on cars, but also for small trucks and vans (i.e. commercial vehicles). Such tires are additionally indicated by the letter C or the word Commercial.

It is impossible to install tires with load and speed indexes lower than those prescribed in the documentation.

As for the speed index, it does not only affect the maximum allowable speed for which the tire is designed. The fact is that you can’t drive for a long time (more than half an hour) at this very maximum speed. This is due to excessive tire wear. In addition, it is life-threatening, because at high speeds the rubber should work in normal, not critical modes. Therefore, it is allowed to drive for a long time at speeds 10 ... 15% lower than the maximum allowable. Such reasoning is especially relevant for bad roads, when the rubber constantly gets into pits, potholes and runs into bumps.

Do not exceed the speed limit and do not drive for a long time at the maximum speeds allowed for rubber.

When choosing tires based on the speed index, as in the case of a load, you cannot choose very “fast” tires. The fact is that the faster the tire is designed for, the softer it is. Accordingly, it will have better and more reliable grip on the road surface. However, this is much wears out faster(remember how often tires are changed at Formula 1 races). That is why it is not recommended to buy very high-speed tires for ordinary cars used in urban areas.

Results

We are sure that the above information will help you understand what the load and speed indices of tires mean, whose designations are located behind the tire size value. This will help you make right choice. At the same time, do not forget to leave a small margin of 10 ... 20% for both indices in order to ensure driving comfort and safety on the road.

And you pay attention to such a characteristic of the tire as the load index. The safety of your ride depends on the selected load index. If for some reason the tire breaks while driving, especially on a slippery surface or at high speed, the car may lose control and this will lead to disaster.

I'll start right away with an example. Take a balloon, inflate it, and then squeeze it hard. burst? If not, they squeezed it weakly; if it did burst, they squeezed it hard. These terms refer to the load on the tire. If a one-year-old child sits on the ball, he may not become anything, and if a stocky man sits down, he will definitely burst, because the allowable load on the ball has been exceeded.

The wheel is still more complicated, because not only is it under pressure, it is also spinning. The more pressure is exerted on the wheel, the greater the load begins to experience the side of the wheel (the part that scurries against the curbs). If the permissible load is exceeded, the cord threads will begin to be damaged and a “hernia” will come out at the wheel, which looks like a bump. If a hernia has come out, it is no longer possible to ride on such a wheel. Firstly, it will no longer spin smoothly, and there will be vibration while driving, and secondly, the tire can collapse at any time.

How to choose a load index

I select the load index based on the maximum mass of my car divided by four. If the car weighs 1400 kg, and I can fill it with 60 liters of gasoline, load 120 kilograms of luggage, and put five people (including sleep) weighing 120 kilograms, then the maximum weight of my car will be 2180 kilograms, or 545 kilograms per wheel, which corresponds to an index of 87, however, if I really plan to drive with such a load, I need to create a reserve, and raise the index by a couple of points, i.e. choose an index of 89, which corresponds to 580 kilograms per wheel.

Maximum load or overload

If the estimated mass of the car has approached the limit mark, or crossed it, and the trip cannot be postponed by any means, drive in compliance with all safety rules. First of all, drive at a speed at which you are guaranteed to be able to keep the car when the wheel is destroyed, and secondly, be prepared for trouble. If you can’t drive slowly, but you don’t want trouble, divide the load into parts, or get rid of unnecessary things on the trip.

Table of tire load indices and their corresponding masses

The load index (aka the index of carrying capacity or bearing capacity) is the name of the maximum allowable weight, under the pressure of which the tire is able to function normally. This indicator is especially important for owners of trucks, since the weight of their cars is constantly changing and can reach huge values.

Features of tires with high bearing capacity

To increase the load index, tire manufacturers use stronger materials and reinforce the roll. Rubber becomes more stable, but its rigidity inevitably increases. This means that the higher the load index, the less comfortable the ride will be. hard rubber not only dampens worse, but also creates a hum during movement. The only way to make the operation of the car more comfortable is to take tires with a lower load index. In this case, the owner will no longer be able to transport the previous amount of cargo, but the car will move more smoothly, and the pressure on the suspension will decrease.

Index decoding

In order to avoid confusion, global tire manufacturers use a single index table in the manufacture of tires. The smallest load index among the existing ones is 0. It corresponds to an indicator of 45 kilograms. This means that a tire with this index is able to withstand loads up to 45 kilograms. Max index- 230 with a corresponding indicator of 33,500 kilograms.

These indicators are optimal, not limiting values. For example, if the load index of a tire corresponds to five hundred kilograms, then this does not mean that with a load of 600 kg the tire will be torn apart. From time to time it is permissible to exceed the recommended load by twenty to thirty percent. But when buying tires, you should focus on the recommended value, which, along with the speed index, is indicated in the technical documents of any car.

Additional markings: ply rating and maximum load

The load index is not the only indicator by which one can judge the bearing capacity of a tire. There is also the concept of ply rating or PR (from the English “ply rating”). The higher this figure, the greater the load the tire can withstand. For example, for passenger cars the ply rate is in the range of 4 to 6 PR, and tires with a PR value of 6-8 are usually installed on minibuses or small trucks. For large-sized vehicles, like agricultural machinery, tires marked "Reinforced" (literally, "reinforced") or XL are used. This tire has the maximum ply and is able to withstand the heaviest loads. Alternative option- the sign "C", that is, "commercial". It is put on tires for Vehicle with a large load capacity.

And yet, the ply rate, as an indicator of the optimal load, is imperfect. Tires of different sizes with the same ply rating are able to withstand completely different loads, so ply rating is not an independent indicator. Today, tire manufacturers use it less and less and indicate the load-bearing capacity on the sidewall.

Sometimes, in addition to the load index, the manufacturer indicates the maximum allowable load in kilograms. To recognize it, you need to find the inscription “max. load" followed by a number.

It is important to consider that the limit load indicator is always indicated per tire. To calculate the coefficient for a car, you need to multiply the value by four.

Relationship between load index and speed index

The bearing capacity coefficient is related to the speed index, which was discussed at the beginning. Let's say the 80R marking means that the recommended speed for the tire is 170 km/h and the maximum load is 450 kilograms. But after all, the load on the tire is directly proportional to the speed: the faster the car moves, the higher the load on the tire. To avoid confusion, on each tire, manufacturers indicate the load factor for the maximum allowable speed. In the example above, a load of up to 450 kilograms would be allowed at a speed of 170 km/h. If you go slower, then you can take more cargo. The reverse is also true: if the pressure on the wheels is reduced, the recommended speed limit can be exceeded. There is a formula: five percent weight reduction allows you to increase the maximum speed by 10 kilometers per hour.

Load capacity and speed factor as elements of the frame size

All Technical information about the tire is indicated on its sidewalls. The name of the manufacturer, model, type of cord, country of manufacture and other data are noted there. Among other information, there is always a block of information on the sidewall, which is called the standard size. Let's take size 185/75R14 82S as an example. Here 185 is the width of the tire in millimeters, 75 is the height in millimeters, R is the type of tire (in this case, radial, but can also be diagonal and denoted by the letter D or diagonally belted and denoted by the letter B), 14 is the diameter of the disk in inches, 82 - load index (475 kilograms), S - speed index (180 km / h).

For large trucks, twin tires are sometimes used. The limit load coefficient for each tire in a pair may vary, and in this case, the load index is indicated for each tire separately, through a fraction.