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.
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).
Below you will find several charts that will help you understand tire sizing numbers, including a load index chart and speed rating chart.
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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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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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 |
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.
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.
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.
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195/65 R15 91 TXL
nine0002 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 take into account when choosing rubber that if you want to put tires with a size of 205/65 R15 instead of the size 195/65 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. nine0003
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 precisely 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. nine0003
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 - 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. nine0003
T - tire speed index. The larger it is, the faster you can drive 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 rubber when the car is constantly moving at the specified speed for several hours.
There are two different markings for American tires. 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 (corresponding 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. nine0003
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).
nine0002 M+S or M&S tire marking (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. nine0003
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 tyres.
Outside and Inside ; asymmetrical 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. nine0003
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 drop in 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. nine0003
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 this 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. nine0003
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 wet braking capability.
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).
nine0003
DOT - Manufacturer's coded address, tire size code, certificate, issue date (week/year).
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For example: you have a 175/70 R13 wheel on your car. Using this table, we determine the profile height of your tire 175 by 70, we get 12.2 cm. If you want to put the tire wider and leave the wheel height the same, then select a value close to 12.2 from the table. nine0063 We get the size 205/60 R13. If you want to increase the size of the disk, leaving the wheel height the same, the following calculations are necessary: 175/70 R13 the profile of this wheel according to the table is 12.2 cm, multiply it by 2 because. the height of the wheel consists of two profile values 12.2x2=24.4 cm. Next, add the size of the disc, R13 is 13 inches, translate into cm. 13x2.54=33cm. Then add the two values 24.4+33=57.4cm.
this is the full height of the wheel. Now, having done some simple calculations, you will understand that you can put 195/50 R15 or 185/60 R14, for these sizes, the wheel height is about the same - 57cm. But we should not forget that with an increase in the width of the tire, it is desirable to increase the width of the disk. Usually, the standard wheel height on the machine can be increased by 1, maximum 2 sizes. Before you change the dimension of the wheel, you can always consult with our highly experienced specialists. In some cases, the car has regular wheels of the same radius, but different widths, and the height of the wheels must be the same. (BMW 7 SERIES front 235/50 R 18, rear 255/45 R18). For all these calculations, this table was created. nine0003
| shk | 155 | 165 | 175 | 185 | 195 | 205 | 215 | 225 | 235 | 245 | 255 | 265 | 275 | 285 | 295 | 305 | 315 | 325 |
| 30 | 7. 6 | 7.9 | 8.2 | 8.5 | 8.8 | 9.1 | 9.4 | 9.7 | ||||||||||
| 35 | nine0159 | 8.2 | 8.6 | 8.9 | 9.3 | 9.6 | 10 | 10.3 | 10.7 | 11 | 11.4 | |||||||
| 40 | 8.2 | 8.6 | 9 | nine0159 9.49.8 | 10.2 | 10.6 | 11 | 11.4 | 11.8 | 12.2 | 12.6 | 13 | ||||||
| 45 | 8.8 | 9.2 | 9.7 | 10.1 | 10.6 | 11 | 11.5 | 11.9 | 12.4 | 12.8 | 13. 3 | 13.7 | 14.2 | 14.6 | ||||
| 50 | 9.8 | 10.2 | 10.7 | 11.2 | 11.7 | 12.2 | 12.7 | 13.2 | 13.7 | 14.2 | 14.7 | 15.2 | 15.7 | 16.2 | ||||
| 55 | 10.2 | 10.7 | 11.3 | 11.8 | 12.4 | 12.9 | 13.5 | 14 | 14.6 | 15.1 | 15.7 | 16.2 | 16.8 | 17.3 | 17.9 | |||
| 60 | 10.5 | 11.1 | 11.7 | 12.3 | 12.9 | 13.5 | 14.1 | 14.7 | 15.3 | 15.9 | 16.5 | 17.1 | 17. 7 | 18.3 | 18.9 | 19.5 | ||
| 65 | 10 | 10.7 | 11.4 | 12.6 | 12.8 | 13.3 | 14 | 14.6 | 15.3 | 15.9 | 16.6 | 17.2 | 17.9 | 18.5 | 19.1 | 19.8 | 20.5 | 21.1 | nine0197
| 70 | 10.8 | 11.5 | 12.2 | 12.9 | 13.6 | 14.3 | 15 | 15.7 | 16.4 | 17.1 | 17.8 | 18.5 | 19.2 | 19.9 | 20.6 | 21.3 | 22 | 22.7 |
| 75 | 11.6 | 12.4 | 13.1 | 13.9 | 14.6 | 15.4 | 16.1 | 16.8 | 17.6 | 18.4 | 19.1 | 19.9 | 20.  |
