265/65r18 Tire Size in Inches
The 265/65r18 tires measure 31.6 inches (802.6 mm) in diameter, with a tread width of 10.43 inches (265 mm) and a wheel diameter of 18 inches (457.2 mm). The tire’s sidewall height is 6.77 inches (172.0 mm), and it has a circumference of 99.3 inches (2522.2 mm).
Understanding Tire Size
The 265/65r18 tire size may look like a random string of numbers and letters, but each part has a specific meaning:
- 265: The tire’s width in millimeters from sidewall to sidewall
- 65: The aspect ratio, or sidewall height, as a percentage of the tire’s width (65% of 265 mm)
- r: Radial construction, the most common type of tire
- 18: The diameter of the wheel in inches
So in everyday terms, this is a tire that’s about 10.4 inches wide, has a sidewall that’s 65% as tall as the tire is wide, is a radial tire, and fits on an 18-inch diameter wheel.
Converting Tire Size to Inches
While tire sizes use metric units like millimeters, many people are more familiar with inches. To convert tire sizes to inches:
- Multiply the first number (width in mm) by 0.03937 to get width in inches
- Multiply the width in inches by the aspect ratio percentage to get sidewall height in inches
- Double the sidewall height and add the wheel diameter to get total diameter in inches
For our 265/65r18 example:
- 265 mm x 0.03937 = 10.43 inches wide
- 10.43 inches wide x 0.65 = 6.77 inch tall sidewall
- (6.77 inches x 2) + 18 inch wheel = 31.6 inches total diameter
So while metric sizing is standard for tires, it’s not too hard to figure out the key dimensions in inches.
Why Tire Size Matters
Having the right size tires on your vehicle is crucial for several reasons:
- Safety: Tires that are the wrong size can negatively impact handling, braking, and overall vehicle control.
- Performance: Tires that are too small may not provide adequate traction, while oversized tires can rub on body or suspension components.
- Accuracy: The speedometer and odometer are calibrated based on tire size, so the wrong tires can make readings inaccurate.
- Longevity: Using the recommended tire size helps ensure even wear and maximum tread life.
Think of tire size like shoe size. Wearing shoes that are too big or too small will be uncomfortable and affect the way you walk. The same is true of tires—the right size helps your vehicle perform as intended.
Alternate Tire Sizes
In some cases, you may be able to use a different tire size than what originally came on your vehicle. This is known as “plus sizing.” Some common alternate sizes for 265/65r18 tires include:
- 275/60r18
- 285/60r18
- 275/55r20
- 285/50r20
The key is maintaining a similar overall diameter and sufficient load capacity. Using our shoe analogy, you wouldn’t wear size 12 if you normally wear a 9, but a slightly different size or width might work.
Always consult a tire professional and your vehicle’s owner manual before changing tire sizes to ensure compatibility and safety.
The Importance of Proper Tire Size
In summary, understanding your tire size is important for selecting the right replacements when the time comes. The 265/65r18 tire size, like all sizes, provides key information about the tire’s dimensions that impact performance, handling, safety, and longevity.
While the numbers and letters can seem confusing at first, breaking them down and converting to inches makes tire sizing more approachable for the everyday driver.
And if you’re ever unsure, consult a knowledgeable tire tech—they’ll help keep you rolling with the proper tire size for your specific vehicle.
Meet Caitlin McCormack, a Tire Size Expert and Blogger Passionate About Everything Related to Tires. With Years of Experience in the Tire Industry, Caitlin Has Become an Expert in Tire Sizes and Their Impact on Vehicle Performance.