Home > Company > Tire Safety > Choosing Tires > Determining Tire Size
Once you have determined it’s time to buy tires, you’ll need to know what size tires are correct for your vehicle. Depending on what you drive, you may be interested in how to find the right tire for your…
This information is usually inside your car’s doorjamb, in your owner’s manual. To ensure your current tire or a replacement tire you may be looking at matches your vehicle’s requirements, it will be good for you to understand how tire sizing works. You may have never paid attention to the string of numbers and letters on every tire, but it’s a gold mine of information.
If you’re unsure of how to read tire measurements from your tire walls, the information and graphics below will tell you how to read tire size, understand and interpret it. If you decide you want to substitute a new size or tire type, consult an authorized tire retailer who can expertly advise you, because many optional tire sizes may have different load capacities and could require wheels of a different rim width or diameter and different inflation pressure.
Not sure you need new tires? Our Tire Replacement Guidance article will help you determine whether it’s time to retire your tires.
Most passenger cars, SUVs and light pickups (1/2 ton and smaller) will come with tires that are either P-Metric or Euro-Metric. For P-Metric tires, you’ll see the letter “P” before the number sequence begins: P225/70R16 97H. P-metric is a designation standardized by the Tire and Rim Association for a “passenger car” tire type. For Euro-Metric there will be no preceding letter before the number sequence begins: 225/70R16 98H. Euro-Metric is a designation standardized by the European Tyre and Rim Technical Organization for a “passenger car” tire type.
Both P-Metric and Euro-Metric size tires are designed to primarily be used on passenger vehicles, which can include cars, minivans, SUVs, and other light duty pickup trucks.
If your vehicle is an SUV, Pickup truck or van, you might see a different type of size designation on your placard that is specific for heavy duty light trucks and vans, especially common on ¾ ton and larger pickup trucks and vans. There are two common size types in this category, LT-Metric and Euro-Metric Commercial (aka C-type). Both size types are metric and so use the same structure as P-Metric and Euro-Metric but have some different characters in the size that differentiate them from their passenger car cousins. LT-Metric tires will have the letters “LT” before the size number sequence: LT245/75R17 119/116R Load Range E. Notice that there are two load index numbers and a Load Range, see the section on Load Index for more info. LT-Metric is a designation standardized by the Tire and Rim Association for a “light truck” type tire.
Euro-Metric Commercial or C-Type tires will look very similar to a passenger Euro-Metric size except that there will be a “C” right after the rim size: 23/65R16C 121/119R. Notice that the C-type tires also have two load index numbers. Euro-Metric Commercial, or C-Type is a designation standardized by the European Tyre and Rim Technical Organization for a light truck type tire. Light truck tires are designed to be used on vehicles capable of carrying heavy cargo and are usually only specified by a vehicle manufacturer on vehicles exceeding a certain load capacity.
Other types of tires that fall into the Metric sizing type are Temporary Spares, they start with “T”. If you see a size that starts with “ST,” that means “special trailer” and is only for use on a trailer.
Regardless of whether you are looking at a P-Metric, Euro-Metric, LT-Metric, Euro-Metric Commercial, T or ST tire the numbers in the size mean the same thing.
The first number to appear in your tire size information is the width, in millimeters, of the correct tires for your vehicle: P225/70R16 91S.
Tire width always refers to the measurement from one sidewall to another. Thus, a tire with the measurement “P225” is for a passenger vehicle and has a nominal width of 225 millimeters.
After the slash mark, the next number you see is for the tire’s aspect ratio, which essentially tells you how tall your tire’s profile is: P225/70R16 91S. Aspect ratios are delivered in percentages. Tire makers calculate the aspect ratio by dividing a tire’s height off the rim by its width. If a tire has an aspect ratio of 70, it means the tire’s height is 70% of its width.
Lower aspect ratio tires, such as a 60 series, generally offer vehicle handling performance advantages over higher aspect ratio tires, such as a 75 series, but a typical trade off can be ride harshness.
After the aspect ratio comes a letter that indicates the type of internal construction maintaining your tire’s stability: P225/70R16 91S.
There are two types of construction that you may see on the sidewall of a tire:
Radial tires are the most common tires on the road in the United States today; thus “R” will usually be shown in the tire size designation. Radial construction means the tire’s internal ply cords are oriented in a radial direction, from one bead over to the other, essentially perpendicular to the direction of rotation. You may also occasionally see RF indicating a run flat tire or ZR indicating a tire that is a speed rating higher than V.
The next number is the diameter code, in inches, of the rim onto which the tire can be mounted. For example, a tire with the P225/70R16 91S would fit a rim with a 16-inch diameter.
Load index can be a confusing subject because there are so many different caveats, but we will try to explain everything here.
The next figure after the rim size in the sequence is your tire’s load index, which tells us how much weight, in pounds, the tire can support when fully inflated: P225/70R16 91S
We call it the load “index” because the number doesn’t tell us the precise number of pounds the tire can carry, at least not by itself. However, the number does correspond to a specific load capacity listed in an index. Beginning with 1 and ending with 150, numbers in the load index represent carrying capacities of 99 to 7385 lbs.
There are two types of load types for passenger tires though, Standard Load and Extra Load. If a tire is Standard Load there will be no markings indicating it but if it is Extra Load the letters XL will appear after the size and load index.
Standard Load Euro-Metric: 215/55R17 94V
Extra Load Euro-Metric: 215/55R17 98V XL
Passenger car tires like P-Metric and Euro-Metric will only have one load index number where LT-Metric and Euro-Metric Commercial (C-Type) will have two numbers separated by a slash.
The first number is the load index if the tire is used in a single application, the second number is the load index if the tire is used in a dual application. Passenger type tires cannot be used in a dual application. Light truck tires will also have a Load Range that is indicated by a letter, such as Load Range E. Load Range is an older term that is still commonly used in the industry so you may hear your tire dealer reference it but the load index numbers are the best way to ensure you have the proper tire.
One important but often misunderstood facet about load index is that the load index numbers between standards organizations (P-Metric vs Euro-Metric) are not necessarily on the same scale. Meaning that two tires in the two different systems that have the same load index number could have different maximum load capacities. This is why it’s important to not only look at the load index number but also verify the actual load capacity.
The final figure in a tire size sequence is the speed rating, which is indicated by a letter: P225/70R16 91S.
Just as your load index number corresponds to a specific load, your speed rating letter corresponds to a particular speed capability based on a standardized laboratory test.
For example, a tire with speed rating “S” is rated for up to 112 mph, while a tire rated “R” is up to 106 mph. Remember that this isn’t a recommended cruising speed. Of course, you should always follow legal speed limits on roadways.
Replacement tires must have the same or higher speed rating as the vehicle’s Original Equipment to maintain vehicle speed capability. If a vehicle has tires with different speed ratings, it is the speed rating of the “slowest” tire that dictates the vehicle top speed.
There is one last sizing type that you should know about, especially if you are in the market for off road tires for a light truck or SUV. It’s called a Flotation size and the numbers in this sizing format are very different from the Metric formats.
Flotation sized tires are similar to LT-Metric tires in application except for a few important points. Number one, they cannot be used in dual applications and number two, an equivalent size tire may have different load capacity than its LT-Metric counterpart.
The first number in the Flotation tire size is the overall diameter in inches. Pretty straight forward.
The second number is the section width (sidewall to sidewall) measurement in inches. Again, fairly simple.
After the section width comes a letter that indicates the type of internal construction: 33X12.50R17LT 120Q.
This is the same as is found in the metric sizing systems.
There are two types of construction that you may see on the sidewall of a tire:
Radial tires are the most common tires on the road in the United States today; thus “R” will usually be shown in the tire size designation.
Radial construction means the tire’s internal ply cords are oriented in a radial direction, from one bead over to the other, essentially perpendicular to the direction of rotation.
The next number is the diameter code, in inches, of the rim onto which the tire can be mounted. For example, a tire with the 33X12.50R17LT 120Q would fit a rim with a 17-inch diameter.
The letters LT will be after the Rim Diameter indicating that this tire type is intended for Light Truck vehicles similar to the LT-Metric and Euro-Metric Commercial (C-Type) tires.
Load Index and Speed Rating have the same meaning and format as the tires using the metric sizing system. Note that since flotation tires cannot be used in a dual application there will be only one load index number instead of two.
Another group of stamping on certain types of tires is the Uniform Tire Quality Grading or UTQG. This grading and stamping is required for passenger car tires (i.e. P-metric and Euro-metric) in the all season and summer categories. Dedicated winter tires, Light Truck (LT-Metric, Euro-Metric Commercial, Flotation) and Motorcycle tires are excluded from this requirement.
Quality grading is designed to make the tire purchase decision easier for you. Ideally, the system is intended to provide simple, comparative data so you can make an intelligent buying decision. However, the ratings are based upon test results achieved under special conditions. This means it’s possible to misinterpret the comparative data as it relates to your individual driving habits, conditions, etc. You should still rely on your service or tire professional for assistance.
Quality grading designates the comparative performance levels of a tire based on government-specified tests but commissioned by the individual tire manufacturers.
All tire manufacturers are required to grade regular and all-season passenger tires in three categories:
UTQG
Treadwear
The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course for 6,000 miles (9,600 km). For example, a tire graded 150 would wear one and a half times as well on the government course as a tire graded 100. However actual tire performance depends on driving habits, road characteristics, service practices, and other factors that can influence the outcome.
Traction Grades AA, A, B and C
The traction grades from highest to lowest are AA (the highest), A, B and C. They represent how well tires stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. C-rated tires will have the lowest traction performance.
WARNING: THE TRACTION GRADE ASSIGNED IS BASED ON A WET BRAKING (STRAIGHT AHEAD) TRACTION TEST AND DOES NOT INCLUDE CORNERING (TURNING) TRACTION.
Temperature Grades A, B and C
The temperature grades A, B, and C represent the tire's resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the tire’s material to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a performance level all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades A and B represent higher levels of performance on the laboratory test wheel than the minimum required by law.
WARNING: THE TEMPERATURE GRADE IS ESTABLISHED FOR A TIRE THAT IS PROPERLY INFLATED AND NOT OVERLOADED. EXCESSIVE SPEED, UNDER INFLATION, OR EXCESSIVE LOADING, EITHER SEPARATELY OR IN COMBINATION, CAN CAUSE HEAT BUILDUP AND POSSIBLE TIRE FAILURE.
DOT Quality Grades
All passenger car tires must conform to other federal requirements in addition to these grades.
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Home > Company > Tire Safety > Choosing Tires > Replacement Guidance
The best way to know if it’s time to buy new tires for your vehicle is to have them inspected by a professional, but there are ways to check them yourself. To meet legal safety standards in the U.S., a tire’s tread needs to be at least 2/32” deep. If the tires do not meet the 2/32” standard or are approaching not meeting it, you should replace your tires. When replacing tires, it’s important to select the right tire size for your vehicle. Not sure what size you need? Learn more about determining tire size.
Tires should also be free of sidewall damage and irregular wear for optimal performance and safety. It’s also a good idea to learn what types of damage can be repaired vs. replaced so that you can safely extend the life of your tires.
You can evaluate your tires on your own through a visual inspection. Start with the tread — the part of the tire that contacts the road surface. Make sure the tire tread is deep enough and worn evenly all the way around without any irregularities. All DOT-regulated tires feature built-in treadwear indicators, commonly called “wear bars”, that will help you see when the tread is getting low. These indicators can be found in various places throughout the tread and will be even with the tread surface when the tread is worn to two-thirty seconds (2/32) of an inch. You should also examine each tire’s sidewall to ensure there is no visible damage.
You can also use the Penny Test to check your tire tread.
This test can be performed in your own driveway in just a few minutes.
The idea of the penny test is to check whether you’ve hit the 2/32” threshold. Here’s how it works:
Check all four tires, especially in areas that look the most worn. If any parts of your tire fail the penny test, it may be time to replace the tire.
Consistent wear around the whole tire is normal. Uneven tread wear could be a sign of improper inflation, wheel misalignment, or a variety of other things. If you see uneven tread wear, you should have a technician inspect your vehicle.
If your tires pass these tests, you may not need to buy new tires just yet.
It’s a good idea to reassess the tread every few thousand miles, or once a month, and even more often if you’re putting a lot of wear on your vehicle or driving long distances.
No matter how new your tire is, Bridgestone recommends checking inflation pressure every month and scheduling regular inspections with a pro. After five years, an inspection is essential to determine if a tire is still road-worthy.
We recommend tires that were manufactured 10 years prior (or longer) be taken out of service and replaced with new tires. Same goes for the spare. If it’s 10 years old, it needs to be replaced, even if it appears new.
It’s important to note that the age of a tire is not the only indicator of whether it needs to be replaced. Many tires will need to be replaced before 10 years of age due to routine tread wear and other conditions such as punctures, impact damage, improper inflation, overloading and more.
If a tire is worn out or otherwise unserviceable from damage or conditions of use, it should be replaced regardless of when it was produced or purchased.
Another common tire-buying question is if it’s necessary to replace all four tires at once. The simple answer is yes. It is recommended to replace all four at once because your tires are key to the performance and handling of your vehicle, it’s important for them to be as identical as possible. If your tires don’t match, one end of your vehicle may not be able to respond as quickly as the other, making it difficult to control. Your tires are what keep your vehicle connected to the road, so having an even surface is vital.
If you are in a situation where you will be replacing fewer than four tires, select tires that are similar to what is currently installed on your vehicle. If you are replacing just two tires, those two tires should only be installed on the rear axle.
You should only consider tires that are within the same category as your existing ones.
If you have a vehicle that came equipped with a staggered fitment (different size tires on the front and back) then you should check your vehicle owner’s manual for replacement recommendations.
There are a lot of risks associated with buying used tires. Since you don’t know the history of the tires, it can be difficult to know if they’ve been previously run under inflated, overloaded or have other unseen internal damage which could lead to an unexpected failure. Used tires might also have uneven wear, which can cause noise, vibration or other problems and may need to be replaced much sooner than new tires. It is best to replace tires with new tires of the same category, size, load capacity and speed rating as recommended by your vehicle’s manufacturer.
When it comes to recalled tires, there is only one position to take.
We do not want anyone driving on recalled tires. We are committed to replacing, free of charge, any Bridgestone or Firestone tire (or other brands warranted by Bridgestone) subject to a customer satisfaction, quality and/or safety recall, at any time. The easiest way for consumers to get answers to questions about recalled tires is to call 1-844-293-7514 or locate an authorized Bridgestone or Firestone dealer to examine the tires in question. You can also check current tire recalls online at the National Highway Traffic Safety Administration site.
There’s no reason to guess. Talk to a tire dealer or other authorized professional so you can make certain you’re choosing the best tire option for your vehicle. Find out if tire rotation and balancing are included with your new tires. If they are not, see if you can bundle the maintenance service. Ask the dealer to outline the manufacturer’s warranty and replacement options to make certain your new investment is protected in the long run, and inquire about any specials they may be offering.
With these tire-buying tips and some trusted ratings in hand, you should be able to confidently pick out new tires.
Bridgestone consistently strives to connect with drivers through our stores, dealers and media campaigns to raise awareness and educate consumers on safe driving and tire safety. We encourage all consumers to learn all they can about tire safety and why it's important to have their tires, including the spare tire, regularly inspected by a qualified professional.
Position on Recall Awareness and Tire Age
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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.
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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 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.
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).
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 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. 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.
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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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Tire size is the main parameter when assembling car wheels. Among drivers, the dimensions of tires are called - standard size. Each disc is designed for a specific tire parameter. Mismatch of factory specifications, and the tires will not fit on the disk due to the small size, or vice versa - they will be too large. What size it is and how it is indicated on the wheel, we will analyze in detail further. nine0003
All drivers paid attention to the large numbers displayed on the side of the wheel in the following order 000/00 R 00. The marking is applied in the indicated sequence. Values may vary. The affixed symbols characterize the size of the tire.
We will consider the example of tires with a size of 185/55 R 14:
And to get the size, you need 185 x 0.55 and get 101.75 mm, a metric measure of the height of the side profile.
Refer to your vehicle owner's manual to find out what size tire your car manufacturer recommends. In the technical specifications / wheels / section, the manufacturer indicates 2-3 types of tires that are recommended for use when operating the machine in different seasons. nine0003
In addition, it is permissible to refer to online or offline directories, where, by the make and model of the vehicle, it is possible to inquire about the size of tires. In addition, some machines are equipped with tire size and recommended pressure plates. The Japanese prefer to inform the car owner in this way.
The performance and maneuverability of the machine depend on the final choice of tires.
Even if the tire is seated in the rim seat, this is not a sign of correct selection. Let's analyze the influence of each tire parameter on driving performance:
The main question in disputes between car owners - how does the width of the profile affect performance? Someone argues that the wider the rubber, the better. Others, on the contrary, prefer narrow wheels. The truth is in the middle. In this case, it is worth considering the fact that for different operating conditions an optimal tire size is required.
As noted above, the width of the profile is directly related to the tread. The higher this value in mm, the larger the area of the contact patch. And this affects such characteristics as: directional stability, handling, fuel consumption, braking distance and the degree of aquaplaning. nine0003
If you operate a car with a volume of up to 2.0 liters in the city, then it is better to choose medium or narrow tires.
The fact is that wide tires will be useless on city streets. And in the case of equipping a car with a powerful power plant and regular trips along the highway, it is recommended to choose tires with a wider profile, but listening to the recommendations of automakers.
The height of the tire profile has become the subject of tuning sports and youth cars in recent years. A lot of motorists are swapping factory rims for more attractive larger diameter wheels, completing the new thing with low profile tires. At the same time, many do not realize that in addition to the appearance, the technical characteristics of the car are changing: handling, maneuverability, fuel consumption, etc. nine0003
In addition, the height of the profile affects the rigidity and comfort of movement, suspension performance and protection of discs from damage. The low profile is good at speed and cornering. But its characteristics noticeably melt off-road, where soft and high rubber is more practical.
