Enter the wheel offset and the suspension hub or spindle centerline into the calculator to determine the scrub radius of a vehicle’s wheel setup. The scrub radius is the distance at the road surface between the tire’s contact patch and the projected centerline of the wheel’s steering pivot point.
Scrub Radius Formula
The following formula is used to calculate the scrub radius:
SR = SH - WO
Variables:
- SR is the scrub radius (mm)
- SH is the suspension hub or spindle centerline (mm)
- WO is the wheel offset (mm)
To calculate the scrub radius, subtract the wheel offset from the suspension hub or spindle centerline measurement.
What is a Scrub Radius?
The scrub radius is an important aspect of a vehicle’s steering geometry. It affects the steering feel, handling, and tire wear. A positive scrub radius occurs when the suspension hub centerline is outside of the wheel’s contact patch, while a negative scrub radius occurs when it is inside. Zero scrub radius is when the two points coincide. Each type has its own handling characteristics and is chosen based on the desired performance of the vehicle.
How to Calculate Scrub Radius?
The following steps outline how to calculate the Scrub Radius.
- First, determine the suspension hub or spindle centerline (SH) in millimeters.
- Next, determine the wheel offset (WO) in millimeters.
- Use the formula from above = SR = SH – WO.
- Finally, calculate the Scrub Radius (SR) in millimeters.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge.
suspension hub or spindle centerline (SH) = 100 mm
wheel offset (WO) = 40 mm
