Compare two tyre sizes — get diameter, circumference, sidewall and your speedometer error.
Type width / aspect / rim for your current and new tyres (e.g. 225/45R17).
See overall diameter, circumference, sidewall height and revolutions per km.
We show how far your speedometer will read off, so you can adjust in the ECU.
A bigger overall diameter means a taller tyre. The calculator shows the diameter for both so you can compare directly, plus the percentage difference.
A larger diameter makes the real speed higher than the speedometer shows. The tool gives the exact % error — many ECUs let you recalibrate the speed/odometer constant.
Most workshops keep overall diameter within ±2-3% of the original to avoid speedometer, ABS and gearing issues.
The desktop Softechpro Solutions software corrects checksums for 260+ ECU families and does DPF/EGR/AdBlue/DTC off, Stage tuning and DTC diagnostics offline.
See pricing — €299 one-time