How To Read Tire Specifications | Decode Sidewall Marks

A tire’s sidewall shows its width, profile, construction, wheel size, load index, speed rating, and build date.

Tire specs look like a jumble the first time you stare at a sidewall. Once you know the order, the code starts to read like a sentence. You can tell what wheel the tire fits, how tall the sidewall is, how much weight it can carry, and whether it suits your car, truck, trailer, or spare.

That matters when you’re replacing one tire, shopping used wheels, or checking a used car. A wrong size can throw off ride quality, braking feel, speedometer accuracy, and load capacity. A bad date code can leave you with a tire that looked fresh in photos but was built years ago.

This article breaks the sidewall into small pieces, then puts it back together so you can read almost any tire at a glance.

How To Read Tire Specifications On The Sidewall

Start with the full size string. A common one looks like P225/60R16 97V. Read it from left to right. Each piece gives you one job the tire must do.

Start With The Size String

The first letter tells you the tire type. P means passenger. LT means light truck. ST is for trailer tires. T marks a temporary spare. If there’s no letter, it’s often a Euro-metric passenger tire.

Next comes the width. In 225, the tire is about 225 millimeters wide from sidewall to sidewall. After the slash, 60 is the aspect ratio. That means the sidewall height is 60 percent of the width. Lower numbers mean a shorter sidewall and a squatter look.

The letter after that shows construction. R means radial, which is what you’ll see on most modern road tires. Then comes the wheel diameter. In 16, the tire fits a 16-inch wheel.

The last part, 97V, is the service description. 97 is the load index. V is the speed rating. Those two marks tell you how much weight the tire is rated to carry and the speed class it falls into when it’s properly inflated and used as intended.

What Each Section Tells You

• Tire type: Separates passenger, light-truck, trailer, and spare tires.
• Width: Shows how wide the tire is in millimeters.
• Aspect ratio: Shows sidewall height as a share of width.
• Construction: Radial is marked with R.
• Wheel diameter: Must match the wheel exactly.
• Load index and speed rating: Finish the story after the size code.

If you want a plain-language breakdown from an industry body, the Tire Industry Association’s sidewall explainer lays out the same code in the order you see it on the tire.

Marks You’ll See Beyond The Main Size Code

The size string is only the start. Tire sidewalls also carry safety and use marks that change what the tire is fit for.

You may see M+S, which points to mud and snow use, or the three-peak mountain snowflake symbol, which marks a tire that passed a winter traction test. You might also spot XL for extra load, Run Flat, or automaker-specific marks for factory fitments.

Then there’s the DOT code. That section includes the Tire Identification Number. The last four digits show when the tire was made: the first two digits are the week, and the last two are the year. A code ending in 2624 means the tire was built in the 26th week of 2024.

On U.S. passenger tires, you may also find UTQG grades for treadwear, traction, and temperature. Those grades help you compare tires in the same broad class, though they are not a shortcut for ride comfort, wet grip, snow grip, or road noise.

Sidewall Mark	What It Means	What You Use It For
P	Passenger tire	Fits most cars and crossovers
LT	Light-truck tire	Fits trucks and vans with heavier loads
225	Section width in millimeters	Checks fitment and clearance
60	Aspect ratio	Shows sidewall height and overall tire shape
R	Radial construction	Confirms the tire’s build type
16	Wheel diameter in inches	Must match the wheel exactly
97	Load index	Shows rated carrying capacity from a chart
V	Speed rating	Shows the tire’s speed class
DOT … 2624	Built in week 26 of 2024	Checks tire age before you buy
UTQG 500 A A	Treadwear, temperature, traction grades	Compares passenger-tire grades in the U.S.

Reading Tire Specs For The Right Replacement

When you replace a tire, don’t copy the sidewall blindly. Start with the vehicle’s tire placard on the driver’s door jamb and the owner’s manual. That gives you the factory size and cold pressure target for the car. The sidewall on the old tire tells you what is mounted now. Those two answers are not always the same.

That gap shows up on used cars all the time. Someone may have upsized the wheels, fitted a cheaper tire with a lower service description, or installed a truck tire on a crossover because the size looked close enough. Close enough is where fitment trouble starts.

NHTSA’s Tire Buyers’ FAQ points buyers to the door label or owner’s manual for the correct size and notes that the last four digits of the DOT code show the week and year the tire was made.

Match These Items Before You Buy

• Size: Width, aspect ratio, and wheel diameter should match the approved fitment.
• Load index: Stay at the vehicle requirement or above it.
• Speed rating: Stay at the requirement or above it unless the vehicle maker says otherwise for a winter setup.
• Type: Passenger, light-truck, trailer, and spare tires are not interchangeable just because the numbers look close.
• Date code: Check age on any tire that has been sitting in a warehouse, a garage, or a marketplace listing.

Common Reading Mistakes

One mix-up trips people again and again: the maximum pressure on the tire sidewall is not your daily inflation target. That mark belongs to the tire. Your car’s recommended cold pressure comes from the vehicle maker.

Another trap is reading the load index as pounds without a chart. The number is a code, not the weight itself. You look up the code to see the rated load. The same goes for speed rating. A letter like H, V, or W is a class mark, not a decoration.

Example Marking	Plain-English Read	What To Check Next
P225/60R16 97V	Passenger tire, 225 mm wide, 60 profile, radial, fits 16-inch wheel, load index 97, speed rating V	Door-jamb label and approved replacement sizes
LT275/65R18 123/120R	Light-truck tire, 275 mm wide, 65 profile, radial, fits 18-inch wheel, dual load indexes, speed rating R	Truck load needs and load range
DOT XXXXXXXX 2624	Made in the 26th week of 2024	Storage history and tread or sidewall condition
UTQG 600 A A	Treadwear 600, temperature A, traction A	How it compares with similar passenger tires
M+S	Marked for mud and snow use	Whether you need a winter-rated tire instead
3PMSF	Passed a winter traction test	Cold-weather use and local seasonal needs

What To Check On A Used Tire Or A Marketplace Listing

Photos can hide the marks that matter. Ask for one clean photo of the full sidewall, one of the DOT date code, and one of the tread across the full width. If the seller only shows the tread face, you’re missing half the story.

Read the full size first. Then check the service description. After that, inspect the date code. A tire with deep tread can still be a poor buy if it’s old, stored badly, or cracked along the shoulder and sidewall.

Also check whether the set is mixed. You may see the same size on all four tires but different load indexes, different speed ratings, or one winter tire paired with three all-season tires. That kind of mismatch can make the car feel odd on the road and can spoil the balance of the set.

A Five-Step Sidewall Reading Habit

1. Read the full size string from left to right.
2. Confirm the tire type, width, aspect ratio, construction, and wheel size.
3. Check the load index and speed rating, not just the size.
4. Read the DOT date code and judge age with condition, not tread depth alone.
5. Match your final choice to the door-jamb label and owner’s manual.

Once you’ve done that a few times, tire specs stop looking cryptic. They turn into a tidy checklist. That makes it easier to shop smarter, spot a bad listing, and choose a replacement that fits the vehicle you drive.