Technical Term
Rolling Radius
The total circumference of the tyre when inflated.
Deep Dive
When changing wheel sizes (e.g., 17" to 19"), you must keep the Rolling Radius the same by chosing lower profile tyres. If the Rolling Radius changes by more than 2.5%, your speedometer will be inaccurate and ABS systems may fail.
Related Concepts
Aspect RatioSpeedometer ErrorUpsizing