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All You Need To Know About P245/40R17 Tire Size

P245/40R17 has a 245 mm section width, a 40% aspect ratio, fits a 17-inch wheel, and has a calculated overall diameter of approximately 24.7 inches with a sidewall approximately 3.9 inches high. The P prefix identifies P245/40R17 as a P-metric passenger tire size. A verified 245/40R17 version also exists with the same nominal dimensions; the P-metric and non-P designations use different load-and-inflation standards, so the designation and service description should still be matched to the vehicle requirements.

P245/40R17 Size Quick Specs

P245/40R17 Dimensions in Inches

The P245/40R17 tire size is approximately 9.6 inches wide, 24.7 inches tall overall, with a sidewall approximately 3.9 inches high. For P245/40R17, the 17-inch figure means the tire is designed for a 17-inch wheel, while the approximately 24.7-inch overall diameter shows how tall the complete tire is.

P245/40R17 in Inches: All Measurements

• Overall Diameter: Approx. 24.7 inches
• Section Width: Approx. 9.6 inches
• Sidewall Height: Approx. 3.9 inches
• Rim Diameter: 17 inches
• Circumference: Approx. 77.6 inches

P245/40R17 Alternative Tire Sizes

Drivers researching alternatives to P245/40R17 also compare P235/40R17 and P245/45R17. P235/40R17 is narrower and has a relatively close overall diameter, while P245/45R17 keeps the same nominal width but adds sidewall height and falls outside the ±3% diameter guideline. Neither comparison alone establishes interchangeability with P245/40R17. The ±3% tire-size guideline is only a starting point; wheel width, load capacity, clearance, and vehicle requirements still need to be checked.

P245/40R17 vs P235/40R17

P235/40R17 has an overall diameter approximately 1.27% smaller than P245/40R17, which is within the ±3% diameter guideline.

• Width Difference: P235/40R17 is 10 mm narrower than P245/40R17.
• Diameter Difference: P235/40R17 is approximately 0.3 inches smaller in overall diameter, a 1.27% decrease from P245/40R17.
• Interchangeability: The P235/40R17 diameter difference is within ±3% of P245/40R17, which makes the swap between two sizes possible and flawless; but that alone does not establish complete interchangeability; wheel width, load capacity, clearance, and vehicle requirements still need to match.
• Practical Difference: P235/40R17 keeps the same 40-series aspect ratio and 17-inch wheel diameter as P245/40R17 but reduces nominal section width from 245 mm to 235 mm.

P245/40R17 vs P245/45R17

P245/45R17 has an overall diameter approximately 3.90% larger than P245/40R17, which falls outside the ±3% diameter guideline.

• Width Difference: P245/45R17 and P245/40R17 have the same 245 mm nominal section width.
• Diameter Difference: P245/45R17 is approximately 1.0 inch larger in overall diameter, a 3.90% increase over P245/40R17.
• Interchangeability: The P245/45R17 diameter difference falls outside the ±3% guideline compared with P245/40R17, so it is generally not recommended as a direct size swap. A larger diameter change can affect speedometer accuracy, vehicle clearance, and the operation of systems calibrated around the original tire diameter.
• Practical Difference: P245/45R17 keeps the same nominal width and 17-inch wheel diameter as P245/40R17 but increases the aspect ratio from 40 to 45, producing a taller sidewall and a taller complete tire.