Tire size number explained


Tire Size Explained: What the Numbers Mean

Tire size can be confusing. Some numbers on the sidewall are listed in millimeters while others are inches. Plus, the right size for your car, truck, or trailer can differ depending on where and how you drive.

You can see your original equipment tire size in your owner’s manual or on the placard generally located on the driver’s side door jam. This is the sizing recommended by the vehicle manufacturer.

If you’re interested in switching out your tires for a different look or performance, a good place to start is the numbers and other indicators on your existing tires’ sidewall. Next, have a tire professional help you determine a tire size range that will fit your vehicle and driving needs.


Tire Size Meanings

Here’s what those numbers and indicators on the sidewall indicate and how to understand them:

A: TIRE TYPE The first letter in the code tells you what class of tire it is.

P stands for passenger vehicle tire. P-class tires include cars, SUVs, crossovers, minivans and smaller pickup trucks.

LT means light truck tire, designed for vehicles that are capable of carrying heavy loads, towing trailers, or for those looking for an extra heavy duty option. These are often equipped on three-quarter or 1 ton trucks and SUVs.

ST stands for Special Trailer. These tire sizes are meant for trailers, including fifth wheels and other travel trailers, as well as boat and utility trailers.

If there’s no letter before the first number, you have a metric tire most commonly referred to as European size. It’s also measured in millimeters but may have a different load capacity than a P or LT tire.

B: TIRE WIDTH The three-digit number following the letter is the tire’s width (from side to side, looking at the tire head on) in millimeters. This may also be referred to as the section width.

C: ASPECT RATIO The forward slash separates the tire width number from the two-digit aspect ratio. The bigger the aspect ratio, the higher/taller the tire’s sidewall, or “profile” as it’s sometimes called.

The aspect ratio is indicated on the tire sidewall as a percentage. It’s the height of the sidewall measured from wheel rim to top of the tread, expressed as a percentage of tire width.

In this example, the aspect ratio is 65, meaning the sidewall is 65 percent as high as the tire is wide. To get the sidewall height, take the tire width of 215 mm and convert it to inches (8.46). Then multiply this by 65% (.65). This gives you an answer of 5.5, the sidewall height in inches.

D: CONSTRUCTION TYPE This single letter tells you about the internal construction of the tire.

R is for radial tires, the industry standard for most tires today. They have better road grip, lower rolling resistance for better gas mileage, ride comfort and durability than previous generations of tires. In a radial tire, the plies — layers of strong cords made of a blend of polyester, steel and fabric and coated with rubber — are laid perpendicular to the direction of travel.

D is for tires built with diagonal (crisscrossed) plies, called bias-constructed tires. They are also called conventional, x-ply, or cross-ply tires. Some motorcycle and trailer tires still use this internal construction.

Some run-flat tires are identified with an F followed by the type of internal construction.

E: WHEEL DIAMETER This two-digit number specifies wheel diameter in inches. It’s the distance between the two bead seat areas (where a tire gets tightly sealed onto the wheel).

F: LOAD INDEX The two-digit or three-digit number that follows the gap specifies tire load index. The load index symbol indicates how much weight a tire can support, based on the following standard chart. In our example, the load index is 89, which indicates the tire has a load capacity of 1,279 pounds, when inflated to the tire’s maximum air pressure rating.

G: SPEED RATING The last letter is the tire speed rating. This indicates the top speed it’s safe to travel at for a sustained amount of time. A tire with a higher speed rating can handle heat better and provide more control at faster speeds. The maximum operating speed of a vehicle is no more than the lowest speed rating of all tires mounted on the vehicle. (Of course, you should always abide by speed limits for safer driving.) Speed rating is usually, but not always, a single letter (see the chart).


Tire Size Charts

Below you will find several charts that will help you understand tire sizing numbers, including a load index chart and speed rating chart.



Buying New Wheels or Changing Your Tire Size?

A tire size calculator is a quick way to see whether the tire size you’re considering will likely fit your car, SUV, sports car, light truck or crossover.

But remember that is only an estimate. It’s important to stay within the sizing tolerances of your vehicle. Tires that are the wrong size could cause some pull in the steering wheel, rub against the suspension or body of your vehicle, reduce clearance on hills, or result in a stiffer or noisier ride.

If you’re considering mounting a different tire size on your vehicle, check with a tire expert. Find out whether the tires and wheels you have your eye on are the right fit for your vehicle’s suspension, gearing, and bodywork. And ask how any differences in revolutions per mile, tire speed, load index, and speed rating will affect your ride quality and vehicle performance.

See how new tires and rims will look on your car or truck using our Virtual Wheels simulator, available at any Les Schwab.

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Using Load Index & Load Range to Pick the Right Tires

When shopping for tires online, you’ll notice the terms load index, load range, and speed rating included within the technical specifications. (You can find these numbers and letters on your existing tires, located after the size of the tire. ) Understanding the meaning of load index and load range can help you find the right tire for your vehicle and your needs. As always, the experts at Les Schwab can answer all of your questions about what tires are right for you, but in this quick article, we’ll cover some of the basics of these indicators.

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Load Index

The load index of a tire is a number that correlates to the maximum safe carrying capacity of the tire when it’s inflated to its maximum pressure. Higher load index ratings mean your tires will be able to handle a heavier load. In this example, there are two numbers. The higher number (load index) is for single rear-wheel applications. The lower number is for dual-wheel applications. This indicates its load-carrying capacity when inflated to its maximum pressure. Remember, air pressure is what carries the load in a tire. You can find each tire’s carrying capacity with the chart below.


LOAD
INDEX
LOAD
(lbs)
LOAD
INDEX
LOAD
(lbs)
LOAD
INDEX
LOAD
(lbs)
65 639 94 1477 123 3417
66 661 95 1521 124 3527
67 677 96 1565 125 3638
68 694 97 1609 126 3748
69 716 98 1653 127 3858
70 739 99 1709 128 3968
71 761 100 1764 129 4079
72 783 101 1819 130 4189
73 805 102 1874 131 4299
74 827 103 1929 132 4409
75 853 104 1984 133 4541
76 882 105 2039 134 4674
77 908 106 2094 135 4806
78 937 107 2149 136 4938
79 963 108 2205 137 5071
80 992 109 2271 138 5203
81 1019 110 2337 139 5357
82 1047 111 2403 140 5512
83 1074 112 2469 141 5677
84 1102 113 2535 142 5842
85 1135 114 2601 143 6008
86 1168 115 2679 144 6173
87 1201 116 2756 145 6393
88 1235 117 2833 146 6614
89 1279 118 2910 147 6779
90 1323 119 2998 148 6944
91 1356 120 3086 149 7165
92 1389 121 3197 150 7385
93 1433 122 3307    
LOAD INDEX LOAD (lbs)
65 639
66 661
67 677
68 694
69 716
70 739
71 761
72 783
73 805
74 827
75 853
76 882
77 908
78 937
79 963
80 992
81 1019
82 1047
83 1074
84 1102
85 1135
86 1168
87 1201
88 1235
89 1279
90 1323
91 1356
92 1389
93 1433
94 1477
95 1521
96 1565
97 1609
98 1653
99 1709
100 1764
101 1819
102 1874
103 1929
104 1984
105 2039
106 2094
107 2149
108 2205
109 2271
110 2337
111 2403
112 2469
113 2535
114 2601
115 2679
116 2756
117 2833
118 2910
119 2998
120 3086
121 3197
122 3307
123 3417
124 3527
125 3638
126 3748
127 3858
128 3968
129 4079
130 4189
131 4299
132 4409
133 4541
134 4674
135 4806
136 4938
137 5071
138 5203
139 5357
140 5512
141 5677
142 5842
143 6008
144 6173
145 6393
146 6614
147 6779
148 6944
149 7165
150 7385
Load Range (Ply Rating)

On some tires, you’ll see a load range indicator on the sidewall, as shown here. Load Range is an older measure of tire carrying capacity equivalent to ply rating. The ply rating isn’t directly tied to the number of plies used in construction, so we recommend using Load Index when appropriate. Load ranges are arranged in alphabetical order starting with the letter “A”. The ply ratings (load range) combined with the tire size tell you the tire load capacity.

The load range on replacement tires must meet or exceed the recommendation on your vehicle’s door placard or owner’s manual. It can be higher than recommended but never lower.

LOAD RANGE PLY RATING
A 2
B 4
C 6
D 8
E 10
F 12

Les Schwab Tip: Some cars, including electric vehicles, may require tires with a higher load range due to weight with and without passengers.


We’re Your Tire Experts

If this seems confusing. Don’t worry. The pros at Les Schwab will show you all of your options, including the size, load range, and load index you need for work, weekends, or your daily commute.

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See also

Numbers and letters on a car tire provide all the necessary information about it. True, it is not easy to read them - here, even in the designation of one parameter, several measurement systems can be used simultaneously. In addition, many values ​​are expressed in special indices. We decipher all important labels for the buyer.

  • What is
  • How to decrypt

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What is a tire label

A tire label is information about its properties printed on the outer rim. This is a huge amount of useful information. Here are the tire parameters that can be read from the tire itself:

  • dimensions;
  • date of manufacture;
  • load capacity;
  • maximum speed;
  • mileage of operation before wear;
  • clutch quality;
  • the most suitable mode of transport;
  • season and weather conditions for its operation.

What does tire marking mean? Therefore, these data are usually the largest and most visible.

The size designation is written in the form XXX/XX R XX. For example 225/65 R17.

The first three digits are the tire width in millimetres. In our case - 225 mm.

The second digit is the height, but not in millimeters, but as a percentage of the width. In our case, its height is 146.25 mm (225 * 0.65).

The third number after R is the outside diameter of the wheel or the inside diameter of the tire in inches. In our case, this is 17 inches or 43.18 cm. Do not confuse - this is the radius, not the diameter. The letter R itself stands for the radial design of the tire, which confuses many. Sometimes Radial can be written separately on the bus - the meaning is the same. In addition to the radial, there is also a diagonal design (D), but these are not found today.

Load and speed indices

Two numbers and a letter immediately follow the size. These are the codes for the load capacity and speed limit of the tire.

Two digits - capacity or load index. This is a complex system of values, in which the larger the number, the greater the load, but the step size between the values ​​is not constant. Therefore, it is easier to just know the most common of them:

  • 75 - 387 kg;
  • 76 - 400 kg;
  • 77 - 412 kg;
  • 78 - 426 kg;
  • 79 - 437 kg;
  • 80 - 450 kg;
  • 81 - 462 kg;
  • 82 - 475 kg;
  • 83 - 487 kg;
  • 84 - 500 kg;
  • 85 - 515 kg;
  • 86 - 530 kg;
  • 87 - 545 kg;
  • 88 - 560 kg;
  • 89 - 580 kg;
  • 90 - 600 kg;
  • 91 - 615 kg;
  • 92 - 630 kg;
  • 93 - 650 kg;
  • 94 - 670 kg;
  • 95 - 690 kg;
  • 96 - 710 kg;
  • 97 - 730 kg;
  • 98 - 750 kg;
  • 99 - 775 kg;
  • 100 - 800 kg;
  • 101 - 825 kg;
  • 102 - 850 kg;
  • 103 - 875 kg;
  • 104 - 900 kg;
  • 105 - 925 kg.

The index value is the load on each wheel separately. To calculate the total load capacity, multiply by 4. This value can also be written elsewhere in a simpler form: Max load - xxx kg.

Photo: Shutterstock

The letter after the two digits of the load index is the index of the maximum speed for which the tire is designed. It starts with A, but the values ​​relevant for modern machines start with the second half of the Latin alphabet:

  • J - 100
  • K - 110
  • L - 120
  • M - 130
  • N - 140
  • P - 150
  • Q - 160
  • R - 170
  • Q - 160
  • R - 170
  • S - 180
  • T - 190
  • U-200
  • H - 210
  • VR - over 210
  • V- 240
  • W - 270
  • Y - 300
  • Z or ZR - over 240.

This is not the limit, but the maximum "comfortable" value. In exceptional cases, you can even exceed it by 20-30%, but it is better to avoid this.

Date of manufacture

Another key parameter is the timing of the tire. Usually it is indicated in a rounded rectangle, but may be without a frame. The first two digits are the week, and the second two are the year.

Wear resistance, grip, temperature

Also, three more parameters are usually indicated on the tire - wear resistance margin, grip quality class and temperature index.

The wear index is denoted by the word treadwear. Its unit is 480 km. Multiply the number next to that word by that value. If treadwear is 400, it means that under test conditions at the test site, such a tire has worn out after driving 192,000 km. Also, this parameter can be designated separately as the abbreviation TWI.

Traction is a measure of how well a tire grips on wet road surfaces. It has values ​​from AA - the best level, to CC - the worst. Tires for regular passenger cars usually have class A, and the highest class is for sports and racing.

Temperature is the tire's ability to withstand heat when driving at a certain speed. There are three values ​​here:

  • A - more than 184 km / h;
  • B - 160-180 km / h;
  • C - 130-160 km/h.

Modern passenger car tires most often have this index value - A.

Photo: Shutterstock

European certificate

The letter E with a number indicates that the tire complies with the rules of the European Tire Standards Association (ETRTO) and has a corresponding certificate . The number indicates the country that issued it - but this does not matter, since the ETRTO requirements are the same. In this case, the tire can be produced anywhere.

Suitable weather

The weather conditions in which it is permissible to use this tire are also usually indicated:

  • M + S - tires for mud and snow;
  • M+SE - for mud and snow with spikes;
  • snowflake icon in a triangle - for severe winter conditions;
  • M + T - dirt and off-road;
  • AGT - all season tires;
  • Water, Rain, Aqua, umbrella icon - the tire is suitable for wet roads.

Winter tires must have a first, second or third designation.

Suitable vehicle class

On some tires you can find the designation of the type of car for which they are intended:

  • P - passenger cars;
  • SUV - all-wheel drive SUVs;
  • C or LI - small trucks, minibuses;
  • ST - special trailer;
  • M/C - motorcycle;
  • T - temporary tire;
  • CMS - mining and construction equipment;
  • HCV - heavy construction equipment;
  • LCM - forestry equipment
  • LPT - trailers.

Other designations

In addition, the tire may be marked:

  • country of origin - Germany;
  • brand name - Michelin;
  • tire brand - Pilot Sport 4;
  • mounting hints, such as the words Inside/Outside, or Rotation with an arrow, direction of rotation of the tire;
  • sealing method: Tl - tubeless tyre, TT - chambered. Tubeless may also be written on a tubeless tire;
  • technical codes and manufacturer's signatures;
  • unique manufacturer's marks indicating that the tires are designed for a particular car model, for example, AO for genuine Audi tires, and a five-pointed star for BMW;
  • DOT code is an American designation that encodes the plant, mold and production batch. This information is of no use to the consumer;
  • marks for assessing tire wear.

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Tire marking. How to correctly determine tire parameters

Do you want to choose a tire for your car, but do not understand tire markings well? 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 right for your car.

Select tires / tire catalog

Explanation of tire markings.

195/65 R15 91 T XL

195 is the tire width in mm.

65 - Proportionality, i.e. profile height to width ratio. In our case, it is equal to 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 consider when choosing rubber that if you instead of size 195/65 R15, if you want to put tires with a size of 205/65 R15, then not only the width of the tire will increase, but also the height! Which in most cases is unacceptable! (except when both of these sizes are indicated in the car's operating book). You can calculate the exact data on changing the outer dimensions of the wheel 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 wheel load is very important.

R - means a tire with a radial cord (in fact, almost all tires are made this way now).

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

15 - wheel (rim) diameter in inches. (It is the diameter, not the radius! This is also a common mistake). This is the “landing” diameter of the tire on the disk, i.e. is the inside size of the tire or the outside of the rim.

91 is the load index. This is the level of maximum permissible load on one wheel. For passenger cars, it is usually done with a margin and is not a decisive factor when choosing tires (in our case, IN - 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 faster you can ride on this tire (in our case, IS - H - up to 210 km / h). Speaking about the tire speed index, I would like to note that with this parameter, the tire manufacturer guarantees the normal operation of the rubber when the car is constantly moving at the specified speed for several hours.

Speed ​​Index Chart:

American Tire Marking:

There are two different American tire markings. The first one is very similar to the European one, only the letters “P” (Passanger - for a passenger car) or “LT” (Light Truck - light truck) are placed before the 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.

Example: 31x10.5 R15 (corresponds to European size 265/75 R15)

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

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

Additional information indicated in the marking 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, then this means that with this index, the tire is able to withstand a maximum load of 670 kg instead of 615 kg (see the table of tire load indices).

M+S or tire marking M&S (Mud + Snow) - mud plus snow and means that the tires are all-season or winter. Many summer tires for SUVs are labeled M&S. However, these tires must not be used in winter, as winter tires have a completely different rubber compound and tread pattern, and the M&S badge indicates good flotation performance.

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

Pictogram * (snowflake) — rubber is designed for use in harsh winter conditions. If this marking is not 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) - special rain tires.

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

RSC (RunFlat System Component) - RunFlat tires are tires on which you can continue to drive a car at a speed of no more than 80 km / h with a FULL 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 tire sidewall indicates a directional tire. When installing the tire, you must strictly observe the direction of rotation of the wheel, indicated by the arrow.

Tubeless - tubeless tire. In the absence of this inscription, the tire can only be used with a camera. Tube Type - indicates that this tire must be used only with a tube.

Max Pressure ; maximum allowable tire pressure. Max Load - the maximum allowable load on each wheel of the car, in kg.

Reinforced or the letters RF in the size (for example 195/70 R15RF) means 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 layers).

Radial this marking on the rubber in the standard size means that it is a radial construction tire. Steel means that there is a metal cord in the tire structure.

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

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

Traction A, B, or C - Tire braking ability on wet road surfaces.

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

TWI (Tread Wear Indiration) - tire tread wear indicators. The marking on the TWI wheel can also be with an arrow. Pointers are located evenly in eight or six places around the entire circumference of the tire and show the minimum allowable tread depth. The wear indicator is made in the form of a protrusion with a height of 1.6 mm (the minimum tread value for light vehicles) and is located in the tread recess (usually in the drainage grooves).


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