Tires are like shoes for your car. And just like shoes, you need to make sure they fit properly! Learning how to read a tire size might seem like a daunting task, but trust me, it’s not rocket science.
In this article, I will break down all the tire size lingo and show you all the incredible information that’s hidden on those sidewalls.
After reading this, you can confidently stroll into the tire shop and tell them you want a tire size of “225/45 R20”. No sweat!
Table of Contents
The Basics of Tire Size
Let’s make things easier to understand. Check out this tire size: P 205/55R16 95H.
Tire Type
P 205/55 R16 95H
- P stands for “P-Metric.” It means the tire meets specific standards set by the United States for passenger vehicles. These include cars, SUVs, small trucks, and minivans.
- LT stands for light truck tires. These tires are designed for vehicles that can carry heavy loads, tow trailers, or want the option for heavy-duty use. These are typically found on three-quarter or one-ton trucks and SUVs.
- ST stands for special trailer tires. These are sized for trailers, including fifth wheels and other travel trailers, as well as boats and utility trailers.
You have Euro metric tires if there’s no letter before the first number. Be careful. These tires can have a different load capacity than P or LT tires.
Tire Width
P 205/55 R16 95H
The first number, ‘205,’ tells you the tire’s width in millimeters. Imagine the tire laid flat – that’s the width from side to side.
Aspect Ratio
P 205/55 R16 95H
The second set of digits, ‘ 55,’ represents the aspect ratio. It’s the ratio of the tire’s sidewall height to its width.
A tire with a LOWER aspect ratio (like 40 or 45) will have a SHORTER sidewall. It will provide better handling and a more responsive feel.
A tire with a HIGHER aspect ratio (like 60 or 70) will have a TALLER sidewall. It can provide a smoother ride and better shock absorption.
Construction Type
P 205/55 R16 95H
Basically, there are two main types of tire construction:
- “R” is for Radial tires. These have layers of cords that go across the tire from bead to bead.
- “D,” “B,” or “–” is for Bias tires (also known as diagonal tires). These have layers of cords that run at an angle to the tire’s direction of travel.
Radial tires are more common these days. They provide better handling, fuel efficiency, and wear resistance.
Besides, some tires have the letter “F” before their construction code. This letter only appears on tires that are designed as run-flat or self-supporting. You know, the ones that can still function for a short distance even if they lose air pressure.
Rim Diameter
P 205/55 R16 95H
The last number, ’16’ in our example, shows the diameter of the rim in inches that the tire is meant to fit. This is the distance between the two bead seat areas where the tire fits tightly onto the wheel.
Upgrading your car’s rims is a great way to give it a fresh look and improve its handling. But before making the switch, you need to consider the CLEARANCE.
You don’t want to end up with wheels that are too big for your car or that rub against the fenders when you turn. That’s just asking for trouble.
Load Index
P 205/55 R16 95H
The load index reveals how much weight a tire can support when it’s fully inflated.
It is typically a two or three-digit number. The higher the number, the more weight the tire can handle.
We call it a “load index” because the number DOES NOT give us the EXACT WEIGHT the tire can handle on its own.
However, the number does correspond to a specific load capacity listed in the index. In this example, the number is 95, which means the tire can hold up to 1521 pounds or 690 Kilograms.
By the way, not all tires have this number. It’s not required by law.
So, if your tire doesn’t have a load index, check your owner’s manual or contact your tire dealer for more information.
Speed Rating
P 205/55 R16 95H
The speed rating tells you the maximum speed the tire is designed for. In this example, the letter “H” indicates a speed rating of up to 130 mph (210 km/h).
REMEMBER! This is NOT the recommended speed for your car! It’s definitely not legal to go over the speed limit.
Besides, a tire with a higher speed rating isn’t necessarily better.
If you mostly drive in urban or suburban areas and seldom exceed 70 or 80 miles per hour, a lower speed rating tire may be perfectly adequate for your needs.
Check out these speed ratings and max speeds for tires – they’re the ones you’ll see most often:
| L | 75 mph | 120 km/h |
| M | 81 mph | 130 km/h |
| N | 87 mph | 140 km/h |
| P | 93 mph | 150 km/h |
| Q | 99 mph | 160 km/h |
| R | 106 mph | 170 km/h |
| S | 112 mph | 180 km/h |
| T | 118 mph | 190 km/h |
| U | 124 mph | 200 km/h |
| H | 130 mph | 210 km/h |
| V | 149 mph | 240 km/h |
Additional Information on the Sidewall
So you’ve got the hang of the basic tire sizes. But get this: more juicy details are on the side of your tire.
Let’s take a closer look!
M+S (M/S) and Severe Snow Conditions
Some tires have this “M+S” symbol, meaning “mud and snow.” These tires have a little extra space between the treads to help in those conditions.
But they are NOT winter (snow) tires and may not even be traditional all-season tires.
And this is where the mountain snowflake symbol next to the M+S label comes in handy.
If the tire has this symbol, then it has significant snow capability. And it should be considered a viable winter tire.
Uniform Tire Quality Grading (UTQG)
This three-digit number helps you gauge a tire’s treadwear, traction, and temperature resistance.
The higher the numbers, the better the tire’s performance in each category.
Treadwear
Treadwear rating is a measure of how long your tires will last. It’s like the durability rating for shoes but for tires. The HIGHER the Treadwear rating, the LONGER your tires should last.
The experts put these tires through strict tests in a controlled setting. And then, they size up the wear against a reference tire.
The reference tire scores a Treadwear rating of 100. The other tires get their grades based on how long they last compared to the reference tire.
So, a tire with a rating of 300 should last triple as long as the reference tire.
But keep in mind these ratings are based on controlled laboratory tests. They COULD NOT reflect real-world driving conditions, so your actual mileage may vary.
Traction
The traction rating tells you how well the tire can grip the road in wet conditions. The grades range from AA, the HIGHEST rating, to C, the LOWEST.
Think of it like this: You wouldn’t want to wear shoes with no grip on a slippery surface, right? The same goes for your tires.
A tire with a high traction rating (AA) provides better grip and handling in wet conditions. Making your drive safer and more enjoyable.
But here’s the thing: this test doesn’t consider how the tire performs in dry conditions or when you’re taking a turn. And since most cars have anti-lock brakes these days, the test is LESS relevant than it used to be.
So, yeah, take that rating with a grain of salt.
Temperature Resistance
The temperature resistance rating tells you how well a tire can handle heat buildup while a long time driving.
It is determined by testing the tire’s ability to dissipate heat at high speeds and under heavy loads.
The rating goes from A to C, with A being the HIGHEST.
Grade C – that’s the BASELINE. It’s the minimum game every passenger car tire has to bring to the table.
If a tire has a lower temperature rating, it means that it may be more prone to overheating and a potential blowout.
So, if you’re driving in hot conditions a lot, you’ll want to look for a tire with an A rating.
DOT Quality Grades
Did you know that EVERY tire sold in the US has to have a DOT label on it? Yeah, it’s true!
The first two or three characters show which factory it was made in. The following five or six characters are specific to the manufacturer. These are used for tracking purposes, like if there’s a recall or something.
But the most crucial part of the DOT label is the last four digits. These give you the production date, so you know how old the tire is and how long it’s likely to last. The first two digits show the WEEK it was made. And the last two digits indicate the YEAR. For example, “0822” means the tire was made in the 8th week of 2022.
They also have an equivalent DOT code for Europe (starting with an “e”). But, not all manufacturers include both codes on the tire sidewall.
Directional Marker
Have you ever noticed the arrows or triangles (sometimes “outside“) on the sidewall of your car’s tires? Those are directional markers, which means you got yourself some directional tires.
These tires usually have a V-shaped tread pattern. It can funnel water away from the center of the tire and reduce the risk of hydroplaning.
But there’s a catch – you can only rotate these tires in one direction. If mounted incorrectly, they won’t perform as well and could even be dangerous.
Luckily, the directional markers make it easy to figure out how the tire should be mounted. Trust me! Anyone can do it.
Maximum Inflation Pressure & Load Capacity
When you see numbers with “PSI” or “KPA” on your tire, that’s the MAX pressure the tire maker suggests.
And if you spot numbers with “LBS,” that’s all about the MAX load your tire can handle when it’s pumped up.
But don’t get it twisted! These numbers aren’t your tire’s sweet spot for pressure or load.
To find the RIGHT tire pressure and load, just check out your car’s manual or that sticker on the driver’s side door jamb.
So, no need to go overboard and max out your tires!
Where to Find Correct Tire Sizes?
You must ensure you get the right size before you put new tires on your ride. There are two ways to find out.
First, you can check out the tires you’re already using. That’s a good way to get the same tires you have now. But there’s a problem with that. If the previous owner put the wrong tires on there, you’re out of luck.
That’s why it’s BEST to check the door frame on the driver’s side. There’s a label that tells you the correct size. You can also find it in the owner’s manual. These measurements come straight from the car manufacturer, so you know you’re good to go.
Making Informed Choices
Armed with this newfound knowledge, you’re ready to select your perfect set of tires.
Consider Your Driving Style: Are you a city cruiser, a highway speedster, or an off-road adventurer? Your driving habits determine the type of tire that suits you best.
Climate Matters: Living in an area with extreme weather conditions? Opt for tires that perform well in those conditions, be it blistering heat or icy roads.
Stay Close to OEM: If you’re not looking for a dramatic change in performance, sticking close to the original equipment manufacturer (OEM) tire size is a safe bet. It keeps things compatible and holds onto the ride characteristics your vehicle was born with. Easy peasy, right?
FAQ
What do the 3 numbers mean on tire size?
The three numbers, such as 205 in 205/55R16, refer to the tire’s width in millimeters. So, in this example, the tire is 205 mm (around 8.07 inches) wide.
How do I read tire sizes in inches?
Let’s make things easier to understand. Check out this tire size in inches: 25X8 R16.
- The first number, 25, is the diameter of the tire in inches.
- The second number, 8, is the width of the tire in inches.
- The “R” stands for radial construction, a common type of tire construction.
- The last number, 16, is the diameter of the rim in inches.
Ta-da! You’ve just cracked the code on reading tire sizes in inches. Easy, right?
Can I use different size tires for the front and rear?
It is doable, but you’ve got to tread carefully.
Some performance or sports cars use wider tires in the rear for better traction and handling. So, it’s an option if you’re aiming for that extra grip in the corners.
But, and this is a big but, it can mess with your car’s balance and stability. Think of it like wearing different shoes on each foot – not the most comfortable or safe choice.
Another hitch is uneven wear. Different-sized tires might wear at different rates. It means you’ll need to replace them at different times.
If you’re considering it, a chat with a mechanic is a wise move.
Are bigger wheels better?
Well, it’s not a one-size-fits-all answer.
Bigger wheels can add a sporty look and potentially offer better handling, but they often come at a cost.
Bigger wheels can lead to a harsher ride and may be more prone to damage from potholes. Plus, they can be pricier.
It really depends on your priorities and the type of driving you do.
