Question

Jonathan replaced the original factory tires (P220/65 R 18) on his pickup truck with (P255/60 R 17) tires. Calculate the circumference of Jonathan’s ORIGINAL tires. Explain your results

Answer 1

The circumference of Jonathan’s original tire is 92 inches.

Answer 2

92 inches

Explanation:

When a tire's size = P220/65 R 18, it means that:

• the rim is 18 inches wide (or 457 millimeters)
• the width of the tire is 8.7 inches (or 220 millimeters)
• the sidewall of the tire is 5.65 inches (or 144 millimeters)
• the 65 shows the relationship between tire width and sidewall (65%)

the total diameter of the tire = 5.65 + 18 + 5.65 = 29.3 inches

the circumference = 2 x π x radius or diameter x π = 29.3 x 3.141592 = 92 inches