How do I know what size my tires are?
Your tire size is printed on the sidewall of each tire and also listed on your vehicle’s door jamb placard. The common format, such as P215/65R16, encodes width, height, construction, and wheel diameter.
Find the size on the tire sidewall
To identify a tire’s size directly from the tire, read the markings on the sidewall. The most important portion usually appears as a sequence like P215/65R16, but you may also see variations such as LT215/85R16 or T125/90R16 for special cases.
- The width in millimeters (the first number, e.g., 215).
- The aspect ratio (the second number, e.g., 65), which is the height as a percentage of the width.
- The construction type (R for radial, D for diagonal) – most modern passenger tires are R.
- The wheel diameter in inches (the number after the letter, e.g., 16).
- Load index and speed rating (the final pair, e.g., 95T, where 95 is the load index and T is the speed rating).
- Optional prefixes or suffixes that indicate tire type or capabilities (P for passenger, LT for light truck, T for temporary spare, XL for extra load, RFT for run-flat, etc.).
Understanding these elements helps you compare sizes quickly and ensures you select compatible replacements.
Where to confirm the manufacturer’s recommended size
Beyond reading sidewalls, you should verify the official size your vehicle is designed to use. This helps maintain safety, handling, and instrument accuracy.
- Look at the driver’s door jamb placard or the fuel-filler door placard for the recommended tire size and the corresponding load/speed ratings.
- Consult the vehicle’s owner’s manual, which lists the original equipment (OE) size and acceptable alternatives.
- Check the VIN-based lookup on the manufacturer’s website or contact a dealership or reputable tire retailer to confirm compatible sizes for your exact model and trim.
Using the manufacturer-recommended size is the simplest way to preserve handling, safety systems, and warranty coverage.
What to know if you’re considering a different size
If you’re thinking about changing from the OE size, a few practical guidelines apply. Changes can affect speedometer accuracy, gearing, traction control, braking, and clearance, so proceed with care.
- Try to stay within a small change in overall diameter, typically within about 3% of the original (OE) size to avoid major performance or ABS-related issues.
- Understand that changing wheel diameter (for example, moving from 16" to 18" wheels) alters ride quality and may require recalibration or adjustments by a professional.
- Be mindful of load rating and speed rating—oversized tires might not be rated for your vehicle’s expected loads and speeds, which can impact safety and warranty.
When in doubt, consult a certified tire technician to compare specific tire models, verify clearance, and assess how a different size would interact with your vehicle’s systems.
Common scenarios and practical tips
Most drivers will encounter a few familiar scenarios when shopping for tires. Here are practical tips to navigate them.
- Replacing worn tires with the same OE size is the simplest and safest option to maintain original performance.
- Upgrading to a larger wheel diameter or a wider tire can improve grip, but may require ensuring adequate clearance and performance compatibility.
- Mixing tire sizes between axles is generally discouraged unless specifically approved by the manufacturer; it can affect handling and stability.
- Spare tires vary in size and type (temporary spares labeled T). Do not use a temporary spare for extended periods unless it is designed for that purpose.
Always verify compatibility with your vehicle’s systems and consult a professional if you’re unsure about a change in tire size.
Summary
To know your tire size, check the sidewall markings (the format like P215/65R16) and confirm the OE size on the vehicle’s door placard or in the owner's manual. If you plan to change sizes, proceed cautiously, keeping overall diameter within a small tolerance and ensuring load/speed ratings and clearance are appropriate. When in doubt, seek guidance from a reputable tire technician to ensure safety and performance.
What does 225 65R17 mean on a tire?
The numbers 225/65R17 on a tire mean it is 225 millimeters wide, has a sidewall height that is 65% of its width, uses radial construction (indicated by 'R'), and is designed to fit a 17-inch wheel rim.
This video explains how to understand tire sizes: 59sTrying to fix $tuffYouTube · Oct 24, 2023
- 225: The width of the tire from sidewall to sidewall, measured in millimeters.
- 65: The aspect ratio, which is the height of the tire's sidewall as a percentage of its width (so, 65% of 225mm).
- R: The tire's construction type is radial, which is the standard for most modern tires.
- 17: The diameter of the wheel rim in inches that the tire is designed to fit.
How can I tell the size of a tire?
This is either an R or a D. Next is the wheel diameter. This refers to the size of the wheel the tire fits. On then we see the load index which refers to the maximum load capacity of the tire.
What does 275 mean on a tire?
On a tire, 275 signifies the tire's section width in millimeters. This is the width of the tire from sidewall to sidewall when the tire is properly mounted and inflated. A tire with a "275" designation is 275 millimeters wide, which is roughly 10.83 inches.
- Section Width: The first three-digit number in a tire's size code (e.g., in 275/55R20) indicates the width of the tire in millimeters.
- Other numbers: The numbers that follow, such as "55" and "20" in the example, represent the aspect ratio (sidewall height as a percentage of the width) and the wheel diameter, respectively.
- Impact: A wider tire like a 275 generally provides better grip and stability compared to a narrower tire, but may also result in slightly reduced fuel efficiency.
What does 265 70R16 mean?
The numbers 265/70R16 refer to a tire's specifications: 265 is the tire's width in millimeters, 70 is the aspect ratio (sidewall height as a percentage of width), R signifies radial construction, and 16 is the wheel's diameter in inches.
This video explains how to read tire size, including the aspect ratio and rim diameter: 24sTire BloggerYouTube · May 17, 2024
- 265: The width of the tire from sidewall to sidewall in millimeters.
- 70: The aspect ratio, which is the height of the tire's sidewall as a percentage of its width. In this case, the sidewall height is 70% of the 265mm width.
- R: Indicates the tire has a Radial construction, meaning the internal plies are laid in a radial pattern.
- 16: The diameter of the wheel (rim) that the tire is designed to fit, measured in inches.
