Chevrolet Tire Size Calculator
Compare tire sizes and calculate sidewall height, overall diameter, circumference, estimated speedometer difference, and theoretical ground-clearance change.
About the Chevrolet Tire Size Calculator
Tire size affects speedometer accuracy, ground clearance, and overall handling. The Chevrolet Tire Size Calculator compares two tire sizes and calculates sidewall height, overall diameter, circumference, estimated speedometer difference, and theoretical ground-clearance change. Enter sizes in the standard format such as 265/70R17.
This is useful when considering an upsized or downsized tire, switching to a different wheel diameter, or checking whether a proposed tire is close enough to the original overall diameter to keep speedometer error small.
Formula used
sidewall height (mm) = (section width x aspect ratio) / 100
overall diameter (inches) = (sidewall height x 2) / 25.4 + rim diameter
circumference = diameter x pi
diameter difference = alternative diameter - original diameter
speedometer error (%) = (diameter difference / original diameter) x 100
actual speed = indicated speed x (alternative diameter / original diameter)
ground-clearance change = diameter difference / 2How to use
- Enter the original tire size and the alternative tire size.
- Optionally enter an indicated speed to see the actual speed.
- Click Calculate to compare the two sizes.
Worked example
Comparing 265/70R17 to 275/65R18: the first has a sidewall of about 185.5 mm and an overall diameter of about 31.6 inches; the second has a sidewall of about 178.75 mm and an overall diameter of about 32.1 inches. The difference is roughly 0.5 inches, or about 1.6 percent, which is small enough that speedometer error stays minor.
Limitations
Calculations are geometric only. They do not confirm wheel fitment, brake clearance, suspension clearance, or load rating. Always confirm tire and wheel compatibility with the vehicle specifications and a tire professional before purchasing.
Frequently asked questions
Will a larger tire affect my speedometer?
Yes. A larger diameter tire makes the speedometer read lower than actual speed; a smaller diameter makes it read higher.
What is the safe size difference?
Many owners stay within about 3 percent of the original overall diameter to keep speedometer error and clearance changes small, but always verify fitment.
Does tire width matter?
Width affects fitment and clearance but the calculator focuses on diameter and sidewall height.