Nearby speed symbols
Defined in UN vehicle regulation.
It is the single letter at the end, right after the load index. Here it is on an example 205/55R16 tyre.
Z Speed symbol
Rated above 240 km/h at its rated load.
More on speed symbol
TyreCalculator — Tyre Size Calculator & Comparison
Enter a tyre size such as 265/65R17 to see its section width, profile, sidewall height, rim diameter, overall diameter, circumference and revolutions per kilometre. Add a second size to compare the two and check whether the swap fits, including the diameter difference, speedometer error and ground-clearance change. This tool needs JavaScript enabled.