Tyre Size Calculator
Compare your current and new tyre size to see the diameter change, speedometer impact, and whether the upgrade is safe to fit.
Current size
New size
Overall diameter change
-0.41%
-2.6 mm
Current diameter
634.5 mm
New diameter
631.9 mm
At an indicated 80 km/h you'll actually do
79.7 km/h
Within the recommended ±3% tolerance — safe to fit.
FAQs
How much tyre size difference is safe?
As a rule of thumb, keep the overall diameter within ±3% of the original. Beyond that, your speedometer reads inaccurately and you risk clearance issues.
What do the numbers in 195/65 R15 mean?
195 is the section width in mm, 65 is the aspect ratio (sidewall height as a % of width), R means radial, and 15 is the rim diameter in inches.
Will a bigger tyre affect my speedometer?
Yes. A larger overall diameter makes the speedometer under-read — you travel faster than indicated. A smaller diameter does the opposite.