Whether a different tyre size fits, and what it does to the speedometer. The aspect ratio is a percentage of the width rather than a fixed height, which is why a wider tyre with the same number is also taller.
Also called: tyre size comparison, plus sizing calculator.
The new tyre is 0.38% different in diameter, which is within the three percent usually considered acceptable. Your speedometer will read 0.38% off, so an indicated 100 becomes an actual 100.4.
Overall diameter is the rim plus two sidewalls, and the sidewall is the aspect ratio percentage of the section width. That relationship is the one people miss: raising the width from 205 to 225 at the same aspect ratio also raises the height, so plus-sizing usually pairs a wider tyre with a lower profile to keep the diameter constant. A diameter change goes straight into the speedometer, since the car counts wheel revolutions.
overall diameter = twice the sidewall height plus the rim diameter in mmEach of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
Difference in overall diameter0.38%
Both computed independently; a well-matched plus size
Open this exampleDifference in overall diameter0%
boundary
Open this exampleDifference in overall diameter20.4%
degenerate case
Open this exampleFormula version 1.0.0 · definition 1.0.0 · United States · Report a problem with this calculator