Comment on Do you need to adjust your speedometer if you change the size of your tires?
Kecessa@sh.itjust.works 4 weeks agoI don’t it because the 14" and 15" tires should have a different second number to their measurement to compensate, the manufacturer wouldn’t recommend installing tires that will make your speedo different depending on your wheel size.
First number is width
Second number is height of the sidewall as a % of the width
Third number is wheel size
So for example my summer tires are 255/45R20, my winter tires are 255/55R18, increasing the sidewalk height from 45% to 55% of the 255mm width compensates for the wheels being 2" smaller
Successful_Try543@feddit.org 4 weeks ago
I know, but still the circumference differs. It’s 195/60R15 vs. 185/65R14
Comparison