Calculating the tyre size: The final step
Now you have to calculate the percentage difference in the rolling circumference of your old and new tyres. A change may not exceed 1.5 to 2.5 percent. These parameters set the tolerance for rolling circumference. The reason is that an excessive difference in the values can lead to complications in integrated systems, such as the ABS or ESP. This is especially true for deviations between the front and rear wheels. That is a substantial impairment that the inspector will not accept. A word of caution: The calculated values serve only as a guide. What tyre circumference is actually allowed is decided solely by your technical inspector.