How to read load index on tires


Understanding Truck Tires: Load Ratings and Sizes

Home / Understanding Truck Tires: Load Ratings and Sizes

Your truck’s tire specs give you more information than you realize in the alpha-numeric code on the side. Learn to read and understand what these letters and numbers mean for your tires’ truck load index, speed rating and size. Understanding these values will make you a better consumer when choosing tires for your truck.

For help selecting which truck body is right for your needs, click here to see all of Reading’s truck bodies.

How to Read Tire Specs

If you take a close look at a tire, you will find a large amount of information. Everything from the manufacturer’s name to the tire size and load rating appears on the sidewall. Interpreting these numbers requires you to know what values to look for and their meanings.

On the sidewall, you will find the tire’s type, the width, aspect ratio, construction, wheel rating, load index and speed rating. You can identify the values based on their position relative to each other and how many numbers or letters they have. The Tire and Rim Association standardizes these values for all American tire manufacturers.

Some tires may also have Uniform Tire Quality Grading, UTQG, which refers to information for traction and temperature grades. AA traction grades perform best in wet conditions, and the classes go down in performance — AA, A, B and C. Temperature categories refer to how well the tires dissipate heat at various speeds. Those rated with A perform well at speeds over 115 mph. B-rated tires operate best between 100 mph and 115 mph, while C tires remove heat best at speeds between 85 mph and 100 mph.

The first part to look for is the string of letters and numbers that may start with P, LT or no letter. For example, P235/75R15 or LT215/65R15. Manufacturers put a lot of information into this alpha-numeric code — the tire type, width, aspect ratio, construction and tire diameter.

Next to this extended code, you will also see the load index and speed rating, both of which you must know to find the right tires for your loaded work truck.

To make the most of this information, you need to understand what the tire size information means as well as the load ratings and speed information.

Truck Tire Sizes Explained

The tire size typically starts with a letter indicating the type and ends with a two-digit number, giving the rim size. Between these parts, you will see additional information about the tire size and construction.

1. Tire Type

The first letter represents the type of vehicle you should install the tire on. P indicates a passenger vehicle or light-duty truck. Generally, these tires require lower pressures than other tires. LT designates a light-duty truck, but these often accompany larger 3/4 and one-ton pickups. If there is not a letter at the beginning, the tire is a Euro-Metric tire, usually used on passenger vehicles. In the example P235/75R15, the P means this tire fits onto a passenger vehicle.

2. Sidewall Width

Look at the three numbers after the letter or the first three numbers in front of a slash mark if your tire does not have a letter at the beginning. These numbers give the measurement of the tire’s width from sidewall to sidewall in millimeters. Most tire measurements come from the metric system, regardless of the company making the tires. The example of P235/75R15 has a width of 235 millimeters between sidewalls.

3. Aspect Ratio

After the slash mark, you will see a two-digit number. This value refers to the aspect ratio, which is the percentage of the sidewall’s height to its width. In the example tire, P235/75R15, the 75 is the aspect ratio. This tire’s sidewall height measures 75% of the width of the sidewall.

4. Tire Construction

Following the aspect ratio, you will see one of three letters — R, B or D. This letter tells you about the tire’s construction. An R designates radial tires, which have their internal cords laid at 90-degree angles to the tire’s centerline.

Bias-ply tires have a D in this position to indicate their diagonal design. On these types of tires, the cords cross each other at 30 to 45-degree angles. While once common early in the 20th century, bias-ply tires no longer dominate the market. They have been replaced by longer-lasting, more comfortable radial tires.

Belted tires have a B to designate their format. These tires mix the diagonal design of bias-ply with added belts inside the construction. While rare, these have applications on some off-road trucks, trailers and antique vehicles.

For the example used, P235/75R15, the R means its construction is radial.

5. Wheel Diameter

While the sidewall width uses millimeters, the wheel diameter, the last digits after the construction letter, comes in inches. The larger the number here, the larger the wheel size. If you replace your rims, you will also need to change the tires to fit. Be careful when changing wheel sizes because larger wheels affect the handling of the vehicle.

In the example tire, P235/75R15, the 15 at the end means you must install it on a 15-inch diameter wheel.

6. Load Index and Speed Rating

Following the size information, you will see two numbers and a letter. The numbers give the load rating for the tire, while the letter indicates the speed rating.

Using P215/65R15 85H as an example, the 85 gives the load index, also called the tire ply rating, and the H is for the speed rating, which tells you the maximum speed at which you should use the tires. This speed ranges from 3 mph to 186 mph.

What Is a Truck Tire Load Range, Ply Rating, Tire Load Index and Tire Speed Rating?

Often, you will see a number and letter following the tire size. This set of information denotes the tire load and speed rating. On some tires, you may see three letters instead of one. The first gives the speed rating while the next two indicate the load range.

1. Tire Load Range and Tire Ply Rating

The tire load range is also known as ply rating — a term that dates back to the days of bias-ply tires, which had different numbers of ply layers. More layers indicated a better and stronger tire. Today, ply rating still refers to the strength of the tire, but since fewer, stronger plies are used, the numbers have been replaced by load range letters.

The load ranges for passenger tires have a listing beneath the tire code with information about the maximum load range and tire pressures. The load range indicates the heaviest load the tire can handle in pounds. Maximum tire pressure indicates the highest you can inflate the tires, but do not fill your tires to this pressure. It reflects the highest pressure the tire can handle when carrying its maximum load. Use the pressure given in your vehicle’s owner’s manual for the ideal tire pressure that creates the most comfortable and safest ride.

Light truck load ranges have letters B, C, D, E and F, and they have increasing maximum pressures. The lowest pressure is for B tires with 35 psi, and C has a pressure of 50 psi. The pressures increase in increments of 15 from 65 psi, 80 psi and 95 psi for tires with load ranges of D, E and F. For work trucks, the most common load ranges are C, D and E. Commercial trucks, which have much higher carrying requirements, have load ranges from F through L.

In some cases, you may see a number after the load range number, for example, C1 or C2. They still have the same number of plies, but the numbers designate differing max pressures.

If you see a pair of load ratings, the tire manufacturer did not make a mistake. Instead, these LT tires have the load ratings for dual tires. The first number gives the load index for the tires when used on single axles. The second number is how much the tire can handle when used on a dual axle.

For instance, if you see a 104/101 for the load index, this means the tire has an index of 104 when used by itself but only 101 when installed on a dual-tire axle. The second number is usually lower because of unequal load sharing when the tires are paired together. However, when the tire is acting by itself, it can support a higher weight.

  1. Tire Load Index

The load index on a tire gives a numerical value for the maximum weight the tire can handle when it is inflated to its recommended pressure. Higher numbers correlate to the tire’s ability to bear heavier loads. Indices start at 1, which can carry 102 pounds, and they go up to 150, which can hold up 7,385 pounds. In the example, P215/65R15 85H, the 85 load index means the tire can carry up to 1,135 pounds.

Like truck tire load ratings, the higher the load index, the more robust the tire is. Higher load indices correspond to tires used for hauling cargo or for installation on work trucks. No matter how strong the tire is, though, it’s important to remember to never carry weights that are heavier than your tires or vehicle’s suspension are rated for.

3. Tire Speed Rating

In addition to load ranges and indices, you also need to know about the speed ratings to keep your truck and cargo safe and to avoid damaging your tires. Just as tires have load indices to limit the amount they carry, they also have ratings for their maximum speeds. In the United States, most speed ratings on tires surpass the limits on highways. You should never exceed the posted speeds, regardless of the ability of your tires. Nor should you drive your truck faster than the tires’ speed ratings.

The speed rating has a designation after the load index number and before the load range letter if present. The lowest speed for tires is 75 mph for L rated tires. Only use these for off-road trucks that cannot reach high speeds due to the rough conditions. Keep in mind that speed ratings do not correlate alphabetically. See the speed ratings for various tires listed below and their standard vehicles:

  • L: Only apply these tires to off-road trucks that will not exceed 75 mph.
  • M: Use with temporary spare tires at no faster than 81 mph.
  • N: These tires have a maximum speed of 87 mph.
  • P: Tires with a P rating, cannot go faster than 93 mph.
  • Q: Q tires are usually winter studded or studless tires and should not exceed 99 mph.
  • R: For heavy-duty LT trucks, the rating may be R, which indicates a speed limit of 106 mph.
  • S: Family vans and sedans use the rating of S to indicate speed maximums of 112 mph.
  • T: Family sedans and vans may also use T-rated tires, which can drive up to 116 mph.
  • U: U tires can reach 124 mph.
  • H: Sports vehicles with H speed ratings can hit 130 mph.
  • V: Sports cars, sedans and coupes often use V-rated tires, which have speed ratings up to 149 mph.
  • W: Exotic sports cars use tires that can reach speeds up to 168 mph and have a W designation.
  • Y: The fastest speed rating — once Z which indicates faster than 149 mph — now is Y, which allows the tires to reach 186 mph.

Typically, for work trucks, speed is not the most critical factor, which explains why a speed rating of R for heavy-duty trucks has a limit of only 106 mph. Those who drive sports cars or race usually require specialty tires built for speed. If you need to haul cargo, look for the load index or range, which will help you to identify the best tires for your operation.

In the example tire, P215/65R15 85H, the H indicates the speed index of up to 130 mph.

Truck Use and Add-Ons

When you install tires onto your truck, choose tire sizes and load ratings recommended by the manufacturer. However, the size and strength of your tires you need for your vehicle will change if you customize it by adding on service bodies, platforms, tow hooks or other features. Ask us about the recommended chassis and tire loads needed for such additions to your truck. By pairing the right tires with your customized work truck, you will ensure peak productivity from the vehicle.

The tires you install on your truck are only one part of customizing your vehicle to your job. Service bodies and similar add-ons transform your purchased vehicle into a work machine. In fact, if you have a service body on your truck, you may need higher rated tires to hold up the extra weight you carry.

Find the service bodies and other ways to customize your truck to perform best at what you do by checking out our products at Reading Truck. If you have questions about the best options or want to create a customized work truck, contact us today.


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A Tire’s Load Index

What Exactly Is Tire Load Index?

When the super smart engineers designed and built your car, they crunched some numbers and determined exactly how much weight it could carry safely based on the right tire size and pressure. This is what we call the “tire load index.” The tires that come on your vehicle will have the proper load index, so stick to that number or higher when you purchase new tires. You can also check the vehicle’s manual to find the recommended tire size and load rating.

Why Is Tire Load Index Important?

The tire load index tells you how much weight your tire can carry, and overloading your tires is never a good idea! When you put too much weight on your tires, you can cause damage and wear them down prematurely. Even worse, you run the risk of experiencing a tire blowout. Imagine trying to carry a box full of cement blocks. Just like your legs would buckle under the weight, your tires can completely give out if they’re overloaded.

Using the Tire Load Index Chart

The tire load index lets you know the load carrying capacity of a tire. In other words, it’s the amount of weight your tire can support safely.

For example, if a tire has a load index of 92, it can support 1,389 pounds at maximum air pressure. Multiply that by four tires (4 x 1,389 = 5,556 pounds) to get your car’s maximum load carrying capacity. Never install tires with a lower load carrying capacity than the original tires that were factory installed on your vehicle.

Tire Load Index Chart

Load- Carrying Capacity Index Ratings
Load Index Load (lbs) Load Index Load (lbs) Load Index Load (lbs)
0 99 50 419 100 1764
1 102 51 430 101 1819
2 105 52 441 102 1874
3 107 53 454 103 1929
4 110 54 467 104 1984
5 114 55 481 105 2039
6 117 56 494 106 2094
7 120 57 507 107 2149
8 123 58 520 108 2205
9 128 59 536 109 2271
10 132 60 551 110 2337
11 136 61 567 111 2403
12 139 62 584 112 2469
13 143 63 600 113 2535
14 148 64 617 114 2601
15 152 65 639 115 2679
16 157 66 639 116 2756
17 161 67 677 117 2833
18 165 68 694 118 2910
19 171 69 716 119 2998
20 176 70 739 120 3086
21 182 71 761 121 3197
22 187 72 783 122 3307
23 193 73 805 123 3417
24 198 74 827 124 3527
25 204 75 852 125 3638
26 209 76 882 126 3748
27 215 77 908 127 3858
28 220 78 937 128 3968
29 227 79 963 129 4079
30 234 80 992 130 4189
31 240 81 1019 131 4289
32 247 82 1047 132 4409
33 254 83 1074 133 4541
34 260 84 1102 134 4674
35 267 85 1135 135 4806
36 276 86 1168 136 4938
37 282 87 1201 137 5071
38 291 88 1235 138 5203
39 300 89 1279 139 5357
40 309 90 1323 140 5512
41 320 91 1356 141 5677
42 331 92 1389 142 5842
43 342 93 1433 143 6008
44 353 94 1477 144 6173
45 364 95 1521 145 6393
46 375 96 1565 146 6614
47 386 97 1609 147 6779
48 397 98 1653 148 6844
49 408 99 1709 149 7165
        150 7385

Considering Load Index When Tire Shopping

As you can tell, the tire load index is massively important when you’re shopping for new tires. When it’s time to select new tires for your vehicle, you must select tires that can support your car’s Gross Vehicle Weight Rating (GVWR). This number can be found in the owner’s manual. To determine if a set of tires will work on your particular car, use the tire load index chart to see how many pounds each tire can support. Multiply that by four (since your vehicle will use four tires). As long as that number is greater than the GVWR of your vehicle, those tires should work. If you think that sounds like a lot of math, don’t worry. Sit back, relax, and let the expert of Tires Plus do the hard work for you. Schedule your appointment for brand new tires today!

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How to Read a Tire Sidewall Mark

How to Read a Tire Sidewall Mark

The sidewall of a tire has all the information you need to know about it. Below you will find a small guide to deciphering all these numbers and letters.

A. Tire width

Tire width from side to side in mm.

B. Section height

Ratio of the section height of a tire to its width, expressed as a percentage. For example, a profile height of 65 means that the height of the tire is 65% of its width

C. Wheel diameter

Wheel diameter (height) in inches.

D. Load index

The maximum load per tire (in kg) depends on the load index. The load index value is printed on the sidewall of the tire to the right of the diameter value.

For example, for a tire with a load index of 91, the maximum load is 615 kg.

When buying new tires, consider the load and speed indexes in combination. In addition, you should always follow the recommendations of your vehicle manufacturer. nine0005

E. Speed ​​Index

The Speed ​​Index is the maximum allowable speed at which a properly inflated tire can be driven under load. The speed index, indicated by a letter, is located after the load index on the sidewall of the tire. For example, for a tire with a speed index of V, the maximum speed is 240 km/h.

When buying new tires, it is important to consider that their speed rating matches the vehicle's speed capabilities.

Higher load indices and other speed indices

Your vehicle may be compatible with tires with load and speed ratings that differ from those specified in the manufacturer's documentation.

However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires and whether their operation is permitted by the current legislation. Always comply with all legal requirements in your country regarding the characteristics of the tires used, and also take into account the recommendations of the vehicle manufacturer regarding speed and load. If necessary, consult your dealer before purchasing or installing tires. nine0005

Is it possible to use tires with higher speed ratings than those recommended by the car manufacturer?

Yes, you can. However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires.

Can tires with higher load indexes be used than those recommended by the car manufacturer?

Yes, you can. However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires. nine0005

Can tires with higher speed and load ratings be used than recommended by the car manufacturer?

Yes, you can. However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires.

Can tires with lower speed ratings be used than those recommended by the car manufacturer?

Yes, it is possible. These can be all-season or winter (M+S) tires with a lower speed index, if: a) a sticker indicating the maximum speed limit is in the driver's field of vision; b) the driver does not exceed the specified maximum speed limit. However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires and whether their operation is permitted by the current legislation. nine0005

Can tires with higher load indexes and lower speed indexes be used than recommended by the car manufacturer?

Yes, it is possible. These can be all-season or winter (M+S) tires with a lower speed index, if:

a) a sticker indicating the maximum speed limit is in the driver's field of vision;

b) the driver does not exceed the specified maximum speed limit. However, it is always worth checking first whether the vehicle manufacturer allows the installation of such tires and whether their operation is permitted by the current legislation. nine0005

Refer to the vehicle owner's manual for load limits. Overloading a vehicle puts unnecessary stress on its tires and other structural elements. This can lead to poor handling, increased fuel consumption and tire damage. Tires may develop large cracks, defects or tears.

Tire type

The presence of the letter "P" or the absence of letters indicates that this is a tire for a passenger car.

Design

The letter "R" stands for radial construction. Most tires manufactured today are radial.

ECE mark and approval number

This mark indicates that the tire meets the United Nations Economic Commission for Europe (UNECE) standards for pneumatic tyres.

Tire pressure information

This is the maximum pressure for your tire. Check your vehicle's owner's manual for recommended tire pressures, which affect your vehicle's handling, cornering and braking behavior, and fuel consumption. nine0005

Tire wear indicators

The letters "TWI" indicate the location of the tire tread wear indicators. You should regularly pay attention to them in order to monitor the degree of tread wear. In most European and Customs Union countries, the minimum permitted tread depth is 1.6mm.

Date of manufacture

The four-digit code indicates the week and year of manufacture of the tire.

Tire load indexes

Every car enthusiast wants new tires to last at least a couple of seasons - this is both convenient and profitable. However, increased loads on the tire can negate all efforts to keep the rubber in good condition for as long as possible. That is why, when choosing new tires, it is necessary to pay attention to such an indicator as the tire load index, the decoding of which contains important information for each driver. On the tire, it is applied next to the speed index and is indicated by numbers - for example, 98T (where 98 is the load index, T is the speed index).

What is the load index and why is it needed

The load index can be loosely referred to as the load carrying capacity of a tire - in other words, it is the load limit of a car equipped with specific tires at the maximum specified speed. The load indexes of passenger car tires range from 60 to 125 units (or from 250 to 1650 kg).

It is worth noting that a variety of indicators influence this parameter: the degree of tread wear, the tire temperature, and much more. To slightly smooth out the influence of these factors, the manufacturer always leaves a margin of safety of at least 20%. nine0005

It is especially important to take into account the load index when moving on domestic roads - the wheel, once in the pit, must withstand the blow. If you do not pay attention to these parameters and load the car more than it is provided, then the likelihood that the tire will not withstand the load increases significantly.

Of course, such coefficients are always calculated with a margin, but it is better to save tire resources for some unforeseen event, and in normal operation it is better to save rubber. After all, tires whose load index is within the acceptable level last longer. nine0005

How to calculate the maximum load capacity of a vehicle?

Consider a specific example - your tire is marked 98 T:

  • coefficient 98 shows that the load on one tire in this case should not exceed 750 kg.
  • , respectively, the load on all four wheels reaches 3000 kg - this is the total load capacity of the tires.
  • Subtract from this number the weight of the car itself (for example, 1600 kg), driver (90 kg) and passengers (85 + 75 kg) and get the potential weight of the cargo that you can load into your car - in this case, 1150 kg. This is the load that your car will withstand at speed 190 km/h

However, the load index is the maximum allowable value, the top, which is not worth climbing. The weight of the car and load is not always evenly distributed between the front and rear axles, and passengers often sit in the wrong place for balance, and therefore there should always be a small margin. The most optimal and safe is the load in the amount of not more than 35% of the total mass of the car. In the end, for the transport of particularly heavy loads, you can always buy tires whose tire load index, the table of which is presented on our website, will be higher. But keep in mind that in this case, the load on the suspension will also increase, and this can lead to its premature wear. nine0005

In conclusion, we note another important nuance - the tire load index should not be less than that indicated on the tires in the basic configuration of the car. Failure to follow this rule may result in an accident. The best solution for calculating the load index is the recommendations of the car manufacturer, indicated in its technical documentation.

Below is a complete table of indexes (coefficients) of load capacity :

nine0198 120 nine0198 47.5 nine0198 203 nine0198 515 9019eight 5600 nine0198 61. 5 nine0198 212 nine0198 670 9019eight 7300 nine0198 99 nine0198 25750 nine0198 143 nine0198 92.5 nine0198 226
LI kg LI kg LI kg LI kg LI kg LI kg LI kg
0 45 40 140 80 450 1400 160 4500 200 14000 240 45000
one 46. 2 41 145 nine0199 81 462 121 1450 161 4625 201 14500 241 46250
2 42 150 82 475 122 1500 162 4750 202 15000 242 nine0199 47500
3 48.7 43 155 83 487 123 1550 163 4875 15500 243 48750
4 fifty 44 160 84 500 124 1600 nine0199 164 5000 204 16000 244 50000
five 51. 5 45 165 85 125 1650 165 5150 205 16500 245 51500
6 53 46 nine0199 170 86 530 126 1700 166 5300 206 17000 246 53000
7 54.5 47 175 87 545 127 1750 167 5450 207 17500 nine0199 247 54500
eight 56 48 180 88 560 128 1800 168 208 18000 248 56000
nine 58 49 185 89 580 129 1850 169 5800 209 18500 249 58000
10 60 fifty 190 9019nine 90 600 130 1900 170 6000 210 19000 250 60000
eleven 51 195 91 615 131 1950 171 6150 211 19500 251 nine0199 61500
12 63 52 200 92 630 132 2000 172 6300 20000 252 63000
13 65 53 206 93 650 133 2060 nine0199 173 6500 213 20600 253 65000
fourteen 67 54 212 94 134 2120 174 6700 214 21200 254 67000
fifteen 69 55 nine0199 218 95 690 135 2180 175 6900 215 21800 255 69000
16 71 56 224 96 710 136 2240 176 7100 216 22400 nine0199 256 71000
17 73 57 230 97 730 137 2300 177 217 23000 257 73000
eighteen 75 58 236 98 750 138 nine0199 2360 178 7500 218 23600 258 75000
nineteen 77. 5 59 243 775 139 2430 179 7750 219 24300 259 77500
twenty 80 nine0199 60 250 100 800 140 2500 180 8000 220 25000 260 80000 nine0199
21 82.5 61 257 101 825 141 2575 181 8250 221 261 82500
22 86 62 265 102 850 142 2650 182 nine0199 8500 222 26500 262 85000
23 87. 5 63 272 103 875 2725 183 8750 223 27250 263 87500
24 90 64 280 nine0199 104 900 144 2800 184 9000 224 28000 264

25 65 290 105 925 145 2900 185 9250 225 29000 265 nine0199 92500
26 95 66 300 106 950 146 3000 186 9500 30000 266 97500
27 97.

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