Short Answer
Complete Explanation
The tire size 275/60R20 is a standardized code that conveys the tire’s main dimensions and construction type.
- 275:
Section width of the tire in millimetres, measured from sidewall to sidewall when the tire is mounted and inflated. - 60:
Aspect ratio, expressed as a percentage, representing the sidewall height as 60 % of the section width. - R:
Indicates radial construction, the most common tire structure in passenger vehicles. - 20:
Wheel (rim) diameter in inches that the tire is designed to fit.
Common Misconceptions
The “60” refers to the tire’s overall diameter in inches.
It is the aspect ratio, a percentage of the section width, not an absolute measurement.
All tires marked “R” are interchangeable regardless of vehicle type.
While “R” denotes radial construction, the load index, speed rating, and vehicle specifications must also match.
FAQ
How is the overall diameter of a 275/60R20 tire calculated?
The overall diameter equals twice the sidewall height plus the rim diameter. Sidewall height = 275 mm × 0.60 = 165 mm. Convert rim diameter to millimetres (20 in × 25.4 mm = 508 mm). Total diameter = (2 × 165) + 508 = 838 mm (≈31.0 inches).
Can a 275/60R20 tire be mounted on a 19‑inch rim?
No. The final number in the code specifies the exact rim diameter the tire is engineered for. Using a different rim size can cause improper bead seating, unsafe handling, and potential tire damage.
What does the speed rating letter mean for a 275/60R20 tire?
The speed rating, indicated by a letter such as H, V, or Z, defines the maximum sustained speed the tire can safely handle. It is not included in the 275/60R20 code itself but appears elsewhere on the sidewall.
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