What does the size comparison calculate?
It derives sidewall height from the width and aspect ratio, then adds the rim diameter to calculate the outer diameter and circumference. The circumference difference is used to estimate the change in indicated versus actual speed.
Why is this not a fitment decision?
Tire size alone does not establish wheel clearance, approved load index, speed rating, axle compatibility, brake clearance or legal compliance. Check the vehicle placard, owner manual and a qualified tire professional before changing sizes.