How to Read Tire Size: 245/35R19 Explained in Plain English
Learn how to read tire sizes like 245/35R19. Understand width, aspect ratio, rim diameter, load and speed ratings, and stock overall diameter.
By Ayoub Farid · · 2 min read
The numbers on a tire sidewall look cryptic but follow a simple pattern. Understanding them is essential when you change wheels.
Decoding 245/35R19 93Y
| Part | Meaning |
|---|---|
| 245 | Tire width in millimeters |
| 35 | Aspect ratio: sidewall height is 35% of the width |
| R | Radial construction |
| 19 | Fits a 19-inch wheel |
| 93 | Load index (maximum load per tire) |
| Y | Speed rating |
Overall diameter
When you change wheel size, keep the tire's overall diameter within a few percent of stock. That keeps your speedometer, ABS and stability control accurate.
Example: going from 17" to 18" wheels usually means a lower aspect ratio (e.g. 45 to 40) so the overall diameter stays similar.
Diameter ≈ rim diameter (in mm) + 2 × (width × aspect ratio / 100)
Width and wheel width
Each tire size has a range of approved wheel widths. Stretched tires (narrow tires on wide wheels) are a stance look but reduce grip and may not be legal or insurable everywhere.
Load and speed ratings
Never go below your car's required load index and speed rating. Heavy EVs and SUVs especially need correct load ratings.
Other markings
- DOT date code: the last four digits show week and year of manufacture.
- XL / Reinforced: higher load capacity.
- Run-flat markings.
- 3PMSF (snowflake): certified for severe snow.
Plan wheels and tires together
Wheel look first, then fitment and tires. Preview wheels on your car with CarForge, then use wheel offset explained and the aftermarket wheels guide to choose sizes.
Frequently asked questions
What does 245/35R19 mean?
A 245 mm wide radial tire whose sidewall is 35% of its width, made for a 19-inch wheel.
Can I put a different tire size on my car?
Often, if the overall diameter stays close to stock and load and speed ratings are met. Check fitment and local rules.
How do I find a tire's age?
Read the DOT code: the last four digits are the week and year of manufacture.
Is a stretched tire safe?
Mild stretch is common, but heavy stretch reduces grip and can be unsafe or illegal.
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