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If you’ve ever looked over the numbers and letters stamped into the sidewall of your tires, you’ll know there’s a lot of information available in a small amount of space. But what does it all mean? Following is a guide to help you understand that information so that you’ll have an easier time determining which tires are right for your vehicle.
Fortunately, the answer to this question is yes. Here, a standard set of interchangeability guidelines is governed by The Tire and Rim Association for all manufacturers of tires in the United States. They also have established relationships with most major tire manufacturers in Japan, Europe, South America, and other parts of Asia.
It’s important to understand that tires come in many different sizes that can determine the tire’s performance, their suitability for your specific vehicle, and their overall appropriateness for your driving needs. It is recommended that you check your owner’s manual to understand what size of tires are correct for your vehicle. The following information about your tire’s size and type may be found on its sidewall:
The letter or letters at the beginning (or end) of this sequence indicates the type of tire: P, LT, ST, or T. Most tires will have the letter P, which is short for “P-metric” or a passenger car type tire. These are typically installed on passenger cars, light trucks, SUVs, and vans. An LT appearing at either the beginning or the end of the sequence indicates the tire is a “light truck” tire, or a tire designed to be used on vehicles that carry high loads or pull heavy trailers. ST indicates a “special trailer” tire, used on (you guessed it) - trailers, while “T” denotes a “temporary” tire, like a “donut spare” you might find in the trunk of your vehicle.
The first set of numbers in the numerical sequence indicates the width of your tire as measured in millimeters from sidewall to sidewall.
Next you will find a slash and then another set of numbers: the aspect ratio, sometimes called the tire’s “profile”. This number is a percentage that indicates the tire’s height vs. its width. In the example above, the aspect ratio of our tire is 65, meaning that this tire’s height is 65% of its width.
While there are exceptions, a lower aspect ratio is often indicative of a sportier, more performance-oriented tire while a higher aspect ratio tends to indicate the tire was designed for other priorities like comfort or rugged durability.
Next you will find a single letter, either a “D”, a “B”, or an “R” which indicates the construction type for the tire. “R” indicates that the tire is a Radial tire and “D” designates that it is a Diagonal (also known as “Bias”) ply tire and “B” means it is a Belted-Bias ply tire .
Today, tires featuring Radial construction are by far the most common type. They are made with layers of fabric cords positioned at a 90’ angle to the center line of the tread. Radials became the dominant type of construction because of their superior fuel economy, traction, ride comfort and especially tread life when compared to earlier types of construction. Diagonal (or Bias) ply tires employ layers of cord which cross each other at a 30’-45’ angle to the center line of the tread. This type of construction dates back to the earliest pneumatic tires. It was the preferred design for many years because of its resistance to damage from poorly paved or unpaved roads and relative ease of construction on the building machines available a century ago. Belted Bias tires combine the diagonal ply casing of Bias tires with belts (usually made of fiberglass) under the tread for increased traction and tread wear vs conventional Bias ply tires. Both Bias and Belted-Bias ply tires are available today primarily as reproduction tires for antique vehicles, though some racing, trailer and off road light truck tires use these types of construction, too.
The next number in the set indicates the rim diameter—sometimes also noted as the wheel diameter. This measurement is almost always given in inches. Though there are exceptions, rim diameters ranging from 13” to 22” are most common for passenger vehicles in North America.
The next number, which is paired with a letter, indicates the load index for that tire. The load index is the maximum amount of weight that an individual tire can carry. Because load indexes for a given tire size may vary, it is important to check to be sure the tire you’re considering meets or exceeds your specific vehicle’s manufacturer’s requirements.
In Europe, some highways have speed limits higher than those in North America – and a few have no limits at all. In order to give drivers and government authorities an indication of a tire’s ability to withstand the stresses associated with elevated speeds, the speed rating system was developed. Simply put, the speed rating is the maximum speed at which a set of properly inflated tires may be driven. In North America, speed ratings are useful mostly as an indicator of a tire’s performance capability – how responsive is its handling, how strong is its braking traction, etc. Since there can be large differences in handling and traction for tires within a given speed category, speed ratings alone shouldn’t be used to determine tire choice. You can find more information about tire speed ratings here.
Close to where the sidewall meets the tread, you will also find the Treadwear, Traction, and Temperature grades. These grades are assigned by each tire maker to its own products. They may be used to make comparisons within a tire maker’s product line, but because of variations in testing procedures, they should not be used to compare tires from one company with those made by another company.
Every tire sold in the United States is required to include a US Department of Transportation (US DOT) Tire Identification Number on at least one sidewall. It is located near the rim, and it starts with the letters DOT. These letters are followed by a sequence of 8-13 letters and numbers that denote that tire’s manufacturing location, its specific size, and the manufacturer’s identifying code. The final four digits indicate the week of manufacture followed by the last two digits of the year of manufacture. For example, 5014 would indicate a tire manufactured during the 50th week of 2014. On the sidewall opposite the one with the full DOT code, only the letters DOT and the first four digits of the code are required.
Information on the materials used in the tire’s internal construction is listed next to the DOT code. This information includes both the ply composition—that is, the number of layers as well as the type of materials that were used in its construction.
Finally, in the area of the sidewall closest to the wheel, you’ll find the tire’s load capacity and its maximum cold inflation pressure. This might be different from the inflation pressure recommended for your vehicle by its manufacturer. That’s because the maximum cold tire inflation pressure stated on the sidewall only indicates the greatest pressure permitted for that tire. It doesn’t state the optimal pressure for a tire mounted on a particular vehicle – that is found on a placard mounted on the vehicle or in its owner’s manual.
You probably know what tire tread is: the part of the tire that makes contact with the road surface. But what you might not know is that the specific tire tread pattern your tire utilizes can impact how your tires perform, such as how they handle and how much traction they provide in different driving conditions. Let’s look deeper at both the elements of tire tread patterns as well as the three types you might run across in your search for new tires: Symmetric tread, asymmetric tread, and directional tread.
The most common tread pattern in use on passenger tires is the symmetric tread pattern. In these types of patterns, the outer and inner sides of the tread are symmetric—that is, they are mirror images of one another. The tread blocks form continuous ribs around the tire. Tires with a symmetric tread may use any type of rotation method – front-to-back, modified X or full X. An example of a symmetric tread pattern is the Bridgestone Ecopia EP422 Plus. At times, you might hear symmetric tread pattern tires referred to as “multi-directional”. This is because the tire can be mounted on the wheel and rotated in any direction without affecting performance.
Another tread type found on passenger tires is the asymmetric pattern. In these types of patterns, the inner and outer halves of the tread are designed with different channels and tread blocks. This design is intended to enhance performance such as water dispersal or dry grip and snow traction. In the example above, the Bridgestone Turanza Serenity Plus all-season touring tire, you can see how the left (outer) side of the tire tread features chunkier tread blocks that provide a larger contact area for increased stability and handling on dry roads. The right (inner) side of the tread pattern features more channels and smaller tread blocks to aid in channeling water away for improved rain traction. Multiple rotation patterns may be used for this type of tire.
Some tire tread patterns are designed for rolling in a unidirectional way, meaning in only one direction. These are called directional tread patterns and are often found in high-performance tires and winter tires. As you can see in the example above, the Potenza RE960AS Pole Position tire features tread elements that form a V-shape. This V-shaped tread pattern helps move water more efficiently from under the contact patch to help boost hydroplaning resistance at higher speeds. Since the channels only work if mounted with the V’s oriented correctly, once the tire is mounted, directional tires can only be rotated using a front-to-back and back-to-front pattern. Directional tires will feature an arrow on the sidewall indicating which direction they need to roll when mounted on the car.
Knowing how to change a tire is a necessary skill for all drivers. If you rely on a cell phone to save you in a roadside emergency, there’s always that chance you will forget to charge it, be out of range, or leave it at home. Flat tires can happen anywhere, and a cell phone is no substitute for knowing how to change a flat tire.
Thankfully, changing a tire isn’t all that hard! Just adhere to the following guidelines to be prepared in case you have a flat.
These items should have come with your vehicle:
If you have misplaced any of these items, or if your car did not come with these items, you should purchase new ones right away. And be sure you’re regularly inflating the spare tire to your vehicle manufacturer’s recommended PSI. You should check the spare’s air pressure every time you check your other tires. Remember to check pressure every month and before long trips or carrying extra load.
Here are some items that don’t come with your vehicle but that you should stow in your trunk or glove box in case you have to change a flat tire:
As soon as you realize you have a flat tire, do not abruptly brake or turn. Slowly reduce speed and scan your surroundings for a level, straight stretch of road with a wide shoulder. An empty parking lot would be an ideal place. Level ground is good because it will prevent your vehicle from rolling. Also, straight stretches of road are better than curves because oncoming traffic is more likely to see you.
Never attempt to change your tire on a narrow shoulder near oncoming traffic. Keep moving (slowly) until you find a safer spot. While driving on a flat risks ruining your rim, replacing a rim is better than being hit by an inattentive driver.
Make sure to consult your owner’s manual and review their specific steps on how to change a flat tire for your vehicle
Your hazard lights or “flashers” will help other drivers see you on the side of the road. To avoid an accident, turn them on as soon as you realize you need to pull over.
Once stopped, always use the parking brake when preparing to replace a flat tire. This will minimize the possibility of your vehicle rolling.
Wheel wedges go in front of or behind the tires to further ensure the vehicle doesn’t roll while you fix the flat tire. If you’re changing a rear tire, place these in front of the front tires. If your flat tire is at the front, put the wheel wedges behind the rear tires.
Bricks or large stones will work just as well as “real” wheel wedges. Just be sure they’re large enough to stop the car from rolling.
If your vehicle has a hubcap covering the lug nuts, it’s easier to remove the hubcap before lifting the vehicle with the jack. If your lug nuts are exposed, you can skip ahead to Step 6.
Use the flat end of your lug wrench to remove the hubcap. This will work for most vehicles, but some hubcaps need a different tool to come off. Consult your owner’s manual for proper hubcap or wheel cover removal procedures.
Using the lug wrench, turn the lug nuts counterclockwise until you break their resistance. You may have to use force, and that’s ok. Use your foot or all of your body weight if necessary.
Loosen the lug nuts about ¼ to ½ of a turn, but don’t remove them completely yet. Save that for when it’s time to remove your tire/wheel from the vehicle.
The right place for the jack is usually beneath the vehicle frame alongside the tire that’s flat. Many vehicle frames have molded plastic on the bottom with a cleared area of exposed metal specifically for the jack. To safely lift and avoid damage to the vehicle, follow the instructions for jack placement in your vehicle owner’s manual.
To prevent the jack from settling under the weight of your vehicle and coming off balance, place a small cut of 2x6” wood beneath it before attempting to raise your vehicle. This tactic is especially helpful on asphalt.
With the jack properly positioned, raise the vehicle until the flat tire is about six inches above the ground.
Never put any part of your body under the vehicle during or after raising the vehicle with the jack.
Now it’s time to remove the lug nuts all the way. Since you've already loosened them, you should be able to unscrew them mostly by hand.
Gripping the tire by the treads, pull it gently toward you until it’s completely free from the hub behind it. Set it on its side so that it doesn’t roll away.
Now place the spare on the hub by lining up the rim with the lug bolts. Push gently until the lug bolts show through the rim.
Put the lug nuts back on the lug bolts and tighten them all the way by hand. Once they are all on, check each one again, tightening as much as possible. You will tighten them with the wrench after lowering the vehicle to the ground.
Use the jack to lower the vehicle so that the spare tire is resting on the ground but the full weight of the vehicle isn’t fully on the tire. At this point, you should tighten the lug nuts with the wrench, turning clockwise, as much as you can. Push down on the lug wrench with the full weight of your body.
Bring the vehicle all the way to the ground and remove the jack. Give the lug nuts another pull with the wrench to ensure they’re as tight as possible.
If the hubcap you took from the flat tire will fit your spare, put it in place the same way you removed it initially. If it doesn’t fit, stow it away with the tire when you stow your equipment.
You have before you a jack, a lug wrench, wheel wedges, your flat tire, and possibly a hubcap. Don’t forget to put all of them in your vehicle before driving away.
You should check the tire pressure of the spare tire to make sure that it is safe to drive on. “T-Type” temporary spares, also called “mini-spares,” require 60 psi (420 kPa). If the tire needs pressure, drive (slowly) to a service station immediately.
Temporary spare tires aren’t made to drive long distances or at high speeds, so drive cautiously until you’re able to visit a tire technician. A professional should be able to determine whether your tire needs a repair or if it’s time to replace it.
Aside from taking your tire to a professional, the above procedure shouldn’t take more than 15 to 30 minutes to change a tire. Just be sure you don’t leave out any steps.
It’s beneficial practice changing a tire in your garage or driveway to ensure you’re ready to handle this situation if it ever happens to you.
Knowing how to fix a flat tire is great, but regular tire maintenance is even more important. In addition to reviewing this guide regularly, remember to do the following:
All of these precautions will extend the life of your tires and reduce the likelihood of a flat. While there’s no way to prevent flat tires completely, proper care can improve performance and ensure your tires last as long as possible.
For drivers who want versatile performance year-round, all season tires are a great option. All season tires are essentially tires that find a balance in performance under multiple road conditions that make them a great choice drivers can rely on throughout the year.
How that balance is achieved can vary widely from specific models of tires, but generally, all season tires tend to have a few characteristics in common. Generally, all season tires are made out of rubber composite compounds that are formulated to perform well under a wide range of weather and temperature conditions.
All season tires tend to have tread blocks in sizes and shapes that can offer biting edges for performance in light snow conditions as well as grip on wet and dry roads. All season tires commonly feature some siping—narrow channels across the tread surface—that help increase traction on wet or icy roads. The unique tread patterns of all season tires typically provide a quiet and comfortable ride for cars, trucks, SUVs, and crossovers alike.
All season tires perform well in wet or dry conditions in warmer weather, but are not intended to provide the sporty feel or highest grip associated with maximum handling performance. Additionally, all-season tires are capable in winter weather, but do not provide optimal performance when driving in more extreme conditions such as deep snow, freezing rain, and black ice. If you are looking for a tire that excels in dry performance or provides extra grip during winter seasons you may prefer dedicated summer or winter tires.
If you enjoy making sharp turns with precision and pushing your performance vehicle to the limits, summer tires may be the right match for your vehicle needs. Summer tires work best on high performance vehicles and are designed to offer the most grip and agility in warmer weather. With optimized construction, rubber compounding, and more tread surface in contact with the road, the performance capabilities of summer tires are generally focused around optimized offer better braking, cornering-handling, and a sporty feel control than most other tires. Not only are these tires ideal for dry conditions, the unique tread patterns of Bridgestone summer tires also help provide solid wet performance with enhanced water evacuation capabilities to help resist hydroplaning. However, summer tires may not be as gas-friendly as many tires, and they may not provide the grip you need in the ice or snow.
If you live in an area that sees icy, snowy winters, you should consider switching to Bridgestone Blizzak winter tires for the winter driving season. When temperatures are below freezing and weather conditions can be unpredictable, our winter tires are ready to perform because of special rubber compounds and deep tread grooves, slots and sipes that maintain rubber flexibility and help grip the road. High sipe density technology gives the tire many biting edges to grip snow and ice, providing traction when it matters most. The multicell tread compound found in many Bridgestone Blizzak tires makes the tire porous like a sponge, capable of displacing the thin layer of surface water when driving on ice, and also helps create impressive traction on snow covered roads. If you live in a northern climate that regularly experiences tough, long winters, our Blizzak tires can offer you the extra tire bite you need for especially snowy, icy roads.
When you’re shopping for all season tires, ask yourself what you value most in your tire and driving experience. As soon as you identify what those needs are, you are able to focus your tire search on finding tires that match your criteria. Do you find yourself driving in wet conditions and value wet performance in your all season tire? An option like Bridgestone’s Potenza RE970 AS Pole Position with continuous center rib and 3-D siping for impressive braking, traction, and handling response might be the best tire for you. Need a tire for your SUV or CUV vehicle that compliments the look of a luxury vehicle, helping to deliver fuel efficiency while offering year-round performance? Bridgestone’s Dueler HL Alenza Plus could be the tire that achieves the right balance of styling and performance to satisfy your needs.
Overall, what a person looks for in an all season tire can vary depending on what you value in your personal driving experience. An all season tire can give you an efficient and quality ride for the many weather conditions you may encounter in your everyday life. Bridgestone all season tires can help you confidently take on the open road and lead you to the journeys you have ahead.
Can you drive snow and winter tires year round? It’s an idea that occurs to many drivers who experience winter weather: If I have to mount snow tires every year, why don’t I just keep them on my vehicle all the time?
Unfortunately, using snow tires year round isn’t recommended. In the long run, it will cost more money than changing them out and could compromise your vehicle’s performance on the road. That’s why tire makers offer different types of tires for different seasons – the best option for you is determined by many factors including climate, driving style, and performance needs.
Here are some specific reasons why year-round use of winter tires is not advised. And if it’s the hassle of tire mounting, unmounting, and remounting that you’re tired of, we’ve included an idea for simplifying that process, too.
All winter tires, whether studless or studded, are made to maintain better traction in extreme cold, and on icy, snowy, or slushy roads. The rubber is able to remain softer, which makes it more flexible, allowing the tire to conform to the road better in extremely cold conditions. This feature, along with deeper tread depths and specialized tread designs, are what make snow/winter tires ideal for inclement winter weather and extreme cold driving conditions.
We use this analogy - tennis shoes. Yes, you can wear tennis shoes on the beach or in the snow, but wouldn't it be better to have flip flops on the beach and boots for the snow? Winter tires are like snow boots for your car.
Winter tires are specially designed for cold temperatures and winter precipitation. Once it gets warm, you won't need deep tread depths to handle snow or biting edges for traction on ice. Here are some specific reasons why using winter tires year round is not recommended.
Faster wear on warm, dry pavement - the tread rubber of winter tires is considerably more flexible than that of all season and summer tires. That same pliable tread rubber that adds traction in winter will wear down quickly in warm temperatures. Summer and all-season tires are built to withstand warm temperatures, providing long wear life.
Decreased performance - In warm weather, winter tires won't provide the same handling capabilities as summer or all-season tires. Imagine if you needed to make a quick maneuver and your tires were soft and squishy. You won't get the crisp response from a winter tire in warm weather. Winter tires need that flexibilitity to handle ice and snow, but it's not as useful in warm weather.
The specialized compounds and tread designs of winter tires are not designed for optimal warm climate performance and wear. Generally speaking, the softer tread of a winter tire will wear out faster in warmer temperatures. If you keep winter tires on your vehicle after winter has come and gone, you will have to replace them sooner than had you removed them for springtime.
That’s why using snow tires year round is more expensive than mounting them seasonally. The sooner they wear out, the sooner you have to replace them.
Driving on snow tires year-round could compromise optimal tread wear and ultimately be more expensive than just changing tires out for the season.
If you were considering year-round use of winter tires because you were tired of having to change them, here’s an idea that could save you time and money. Purchase wheels with the same diameter and bolt pattern as your current wheels. Mount your snow tires on those and store them in the garage until winter arrives.
Instead of having to change out your tires each season, just have a technician change the wheels. It’s a quick, relatively inexpensive alternative to mounting and unmounting snow tires every season.
Many drivers ask themselves: “Do I need winter tires if I have all-season tires on my car?” The short answer is, possibly. To understand what tires you'll need, you must first understand the differences in winter tires vs. all-season tires. Every driver's needs are different depending on the weather and road conditions they encounter throughout the year.
Many vehicles are fitted with all season tires when they leave the factory. Since they are built to provide a relatively quiet ride, good tread life and year-round performance, its no wonder why they are so popular. All season tires offer versatile performance and are designed to perform in a variety of conditions including wet roads and light winter driving. All season tires are designed to offer a combination of benefits from summer and winter tires.
In order to provide good performance in a variety of driving conditions, all-season tires inevitably have to compromise some max summer and winter performance capabilities.That means all-season tires won’t provide the same amount of extreme grip and sharp handling of a summer tire. Likewise, an all-season tire is not designed to handle extreme winter conditions like trekking through snow or driving on ice. Think of all-season tires like tennis shoes. You can wear tennis shoes all year, but they aren’t ideal for all situations. It’d be much better to have flip flops on the beach in the summer and boots for the snow.
All-season tire technology offers great year-round performance for drivers who live in moderate climates and do not frequently encounter extreme cold, ice, and snow in the winter months.
When it comes to driving in winter weather, having the right tire matters. From heavy snowfall to black ice, winter roads are extremely unpredictable. These conditions challenge tires to provide traction like no other season of the year. The combination of cold temperatures, ice, and snow can be best met by winter tires, which are specially designed to perform in winter conditions.
There are specific features of winter tires that make them unique: tread rubber, tread depth and patterns, and biting edges.
The Tread Rubber - In extreme cold temperatures, the tread rubber of an all season or summer tire stiffens and becomes less able to provide sufficient traction. To combat this, tread rubber compounds of winter tires are designed to remain flexible, allowing the tire to grip the road better.
The Tread Depth and Patterns - A unique feature of winter tires is deeper tread depths and unique tread patterns. Deeper tread depths reduce snow buildup and provide better traction on the snow. Winter tire tread patterns are designed to channel snow and slush and expel water.
Biting Edges - Winter tires also feature an increased number of biting edges and high sipe densities, or in other words, thousands of tiny slits in the tread that provide traction on ice.
Bridgestone Blizzak tires also feature a proprietary multi-cell compound that acts as a sponge to help remove the thin layer of water that resides on ice and cause slippage. This helps to improve traction in icy conditions so you can maintain control of your vehicle.
The solution to the winter or snow tires vs. all-season tires question will depend on where you live and the conditions in which you drive. If you only see a few snow flurries each year and slick, icy roads are more of a fluke than an annual ordeal, all-season tires are probably the way to go. But if you know there’s a period when icy roads are always an issue, mounting winter tires isn’t an over-the-top precaution – it’s an essential safety measure that could save your life. When mounting winter tires for the season, always install a full set. Just changing out the front tires increases the likelihood that the rear tires will skid. Likewise, just putting snow tires on the rear wheels could cause the front tires to lose traction and make it impossible to steer your vehicle. And remember to re-mount those all-season tires when spring rolls around. While winter tires are undeniably superior in extreme winter conditions, they’ll wear down faster on warm, dry pavement. Shop Snow or All-Season tires and view product level tire technology details that are compatible with your driving needs.