Tire Size Guide: Understand Every Number and Letter on Your Tires Quickly
At first glance tire size can look perplexing, but it is easy to understand once you know what the numbers and letters mean. Every vehicle tire has a code inscribed on the sidewall that provides you crucial information including width, height, construction type, wheel diameter, load capacity and speed rating.
Reading tire size is useful for you:
Buy the right replacement tyres
Increase car safety
Gas mileage
Protect suspension and wheel performance
Avoid costly fitting mistakes
This ultimate guide will teach you exactly how to read tire size step by step in the easiest way imaginable.
What is a Tire Size?
Tire size is a combination of letters and numbers stamped on the side wall of a tire. It shows the size and the specs of the tire.
Here is an example of which:
P215/65R16 95HEach part has a specific meaning.
Decoding Tire Size Numbers
Now, let’s take each section, one by one.
Sample Tire Size
P215/65R16 95H
1. Type of Tire - "P"
First letter tells you what kind of tire.
Common tire type letters are:
| Letter | Meaning |
|---|---|
| P | Passenger vehicle |
| LT | Light truck |
| ST | Special trailer |
| T | Temporary spare |
So in our example:
P215/65R16
“P” refers to passenger car tire.
2. “215” — Tire width
The first is the width of the tire in millimeters.
215 mm;
This means that the tire is:
Width 215 mm
Sidewall-to-sidewall measurement
Wider tyres generally provide:
Keep on the road
Improved Handling
More sporty look
Though it might reduce fuel economy a bit.
3. 65” – Aspect Ratio
The second is the ratio of the sides.
That is the tire sidewall height as a percentage of the width.
Sidewall HeightTire Width×100=65\frac{\text{Sidewall Height}}{\text{Tire Width}}\times100=65Tire WidthSidewall Height×100=65
In this instance:
Sidewall height 65% of 215 mm.
Lower aspect ratios tend to mean:
Better cornering
Sportier handling Stiffer suspension
Higher ratios indicate:
More comfort.
Better shock absorption
4. “R” radial construction
The letter "R" stands for radial construction.
R = Radial Tire
Modern cars are fitted with radial tires because they offer:
Increased Durability
Fuel Efficiency
More tyre mileage.
Ride better
Most modern cars come with radial tires as standard equipment.
5. Wheel size – “16”
The next number is the size of the wheel in inches.
16"
That means the tire is OK:
A 16 inch rim wheel
You will always have to have this size to be exact fit for your wheel.
If the diameter is wrong it won’t fit correctly.
6. Load Index - “95”
The load index tells you how much weight the tire can safely carry.
Consider this as an example:
95 = 1,521 lbs (690 kg)
The higher the number, the more weight it can carry.
Choose the right load index for:
Vehicle performance Stability Security
7. “H” = Speed Rating.
The last letter in the name tells you the tire’s top speed capabilities.
Normal speed ratings:
| Rating | Maximum Speed |
|---|---|
| S | 112 mph |
| T | 118 mph |
| H | 130 mph |
| V | 149 mph |
| W | 168 mph |
In our example:
H = Up to 130 mph
Always choose a tire with the recommended speed rating or higher.
How to Find Your Tire Size
You can see the tire size in a couple of places:
On the tire’s sidewall
Good place to look.
Find a sequence such as:
P215/65R16 95H
Back of Driver’s Door (2)
Inside the driver side door jamb of most vehicles is a sticker that says:
Recommended tire size
Owner’s Manual Load specifications Tyre pressure
Your manual will have the acceptable tire requirements by the manufacturer.
Why Tire Size Is Important
Using the correct tire size is very important.
Some of the things that can happen with wrong tire size are;
Poor handling
Inaccuracy of the speedometer
Fuel economy lowered
Brake performance issues
Tyre rub
Damage to the suspension
Always adhere to the manufacturer’s guidelines.
How To Read Truck Tire Size
Truck tires typically start with:
LT
Example:
LT275/70R18
Here:
- LT = Light Truck
- 275 = Width in mm
- 70 = Aspect ratio
- R = Radial
- 18 = Rim diameter
Truck tires are designed for:
- Heavy loads
- Off-road use
- Towing performance
Metric Versus Flotation Tire Size
Some off road tires are flotation sized.
35x12.50R20
Meaning:
| Number | Meaning |
|---|---|
| 35 | Overall tire height |
| 12.50 | Tire width |
| R | Radial |
| 20 | Rim diameter |
These are common on lifted trucks and SUVs.
New Tires - Buying Tips
Check All 4 Tires
If your car isn't designed for staggered setups, make sure all tires are the same size.
Speed and Match Load Ranks
Do not let these ratings fall.
Evaluate Road Conditions
Select tires for:
driving on the freeway
Rain performance.
Weather conditions
Tire Replacement in Sets for Off-road Application
Always change two tires at a time to keep handling balanced.
Tire Size Questions Most Popular
Can I Use a Different Size Tire ?
Sure, sometimes, but within the limits specified by the manufacturer.
Size matters, and getting it wrong could impact:
ABS systems.
Calibrate speedometer
Stroke of suspension
What's The Most Important Tire Size Number?
All numbers count. The wheel size has to be right.
Bigger tire size = better performance?
Not really.
Bigger tires might add grip and looks but might detract:
Gas mileage
Comfort of riding* Speeding up
How to Read Tire Size - Fast Example
For example:
P225/45R17 91V| Part | Meaning |
|---|---|
| P | Passenger tire |
| 225 | Width in mm |
| 45 | Aspect ratio |
| R | Radial construction |
| 17 | Wheel diameter |
| 91 | Load index |
| V | Speed rating |
Summary
Learning how to read tire size is a skill every vehicle owner needs. With the numbers and letters on the sidewall, you’ll have an easier time picking out the right tires.
The main things to remember are:
Ratio width/height
Construction type
Diameter of Rim.
Loading index
Speed Rating
Always use the tire size recommended by your vehicle manufacturer to achieve the best balance of safety, comfort and performance.
With this knowledge you can confidently go tire shopping, compare your options and keep your vehicle safely on the road.
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