The size designation found on a tire’s sidewall provides the measurements that determine its physical dimensions and the type of wheel it fits. Understanding this standardized code is necessary for selecting the correct replacement or upgrade tire for any vehicle. This article explains the specific metric size 265/70R17 and how large this particular tire is.
Decoding the Tire Size Numbers
The sequence 265/70R17 is a metric designation that breaks down into four distinct pieces of information regarding the tire’s structure and fitment. The first number, 265, quantifies the tire’s section width in millimeters. This is the measurement from the widest point of the outer sidewall to the widest point of the inner sidewall.
The number 70 represents the aspect ratio, which is a percentage that defines the height of the tire’s sidewall. This height is 70 percent of the section width, influencing both the ride comfort and the tire’s overall diameter. A lower aspect ratio indicates a shorter sidewall, while a higher number signifies a taller sidewall.
The letter “R” indicates the tire’s internal construction method, standing for Radial. Radial construction means the tire’s internal body plies run across the tire radially, which is the design used in nearly all modern passenger and light truck tires.
Finally, the number 17 specifies the diameter of the wheel rim that the tire is designed to mount onto, measured in inches. Therefore, a 265/70R17 tire is engineered to fit a wheel that measures 17 inches across its diameter.
Specific Measurements of 265/70R17
Translating the metric code into physical size requires converting the measurements. The section width of 265 millimeters translates to approximately 10.43 inches across the tread when the tire is mounted and properly inflated. This width establishes the tire’s footprint on the road surface.
The sidewall height is derived by taking 70 percent of the 265 mm width, resulting in 185.5 millimeters. Converting this to the imperial system shows the sidewall measures about 7.30 inches from the edge of the rim to the top of the tread. This sidewall height contributes to the tire’s ability to absorb road irregularities.
To determine the overall diameter, the rim diameter must be combined with the height of both sidewalls. The calculation involves adding the 17-inch rim diameter to the two 7.30-inch sidewall heights, resulting in an overall tire diameter of approximately 31.6 inches. This overall height is around 804 millimeters, which is a common size for light trucks and SUVs.
Real-World Fitment Impact
The physical dimensions of a 265/70R17 tire make it a common size for light-duty trucks, full-size SUVs, and some off-road vehicles. Its 31.6-inch diameter is beneficial for increasing the distance between the vehicle’s undercarriage and the ground. This provides a measurable improvement in ground clearance, which is advantageous for off-road driving or navigating uneven terrain.
Common vehicle models that frequently utilize this size include the Chevrolet Silverado, Ford F-150, Jeep Wrangler, and Toyota Tacoma. When a vehicle owner replaces a different stock size with a 265/70R17, the increase in overall diameter affects the distance the tire travels per revolution. This change directly impacts the vehicle’s computer systems, specifically the speedometer and odometer readings.
If the 265/70R17 tire is larger than the original equipment size, the vehicle will be traveling faster and farther than the dashboard indicates. A small difference in diameter can cause the speedometer to be off by several miles per hour at highway speeds, potentially requiring a recalibration of the vehicle’s computer system to ensure accurate readings.