1. What Is Scrub Radius?

Scrub radius is the distance in the front view between the point where the kingpin axis intersects the ground and the center of the tire contact patch. It affects steering feel, stability, and tire wear in vehicles.

2. How Does the Calculator Work?

The calculator uses the scrub radius formula:

Where:

• \( Kingpin\ Offset \) — Distance from wheel centerline to kingpin axis (mm)
• \( Tire\ Offset \) — Distance from wheel centerline to tire contact patch center (mm)

Explanation: A positive scrub radius means the kingpin intersection point is outside the tire center, while negative scrub means it's inside.

3. Importance of Scrub Radius Calculation

Details: Proper scrub radius ensures stable straight-line tracking, reduces torque steer, and prevents excessive tire wear. It's crucial for vehicle suspension design and alignment.

4. Using the Calculator

Tips: Enter both kingpin offset and tire offset in millimeters. Values must be non-negative numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical scrub radius value?
A: Most vehicles have a small positive scrub radius (0-25mm). Zero or slightly negative scrub is also common in modern designs.

Q2: How does scrub radius affect braking?
A: Excessive scrub radius can cause steering pull during braking and increase steering effort.

Q3: Can wheel changes affect scrub radius?
A: Yes, changing wheel offset or tire size alters scrub radius, which may affect handling characteristics.

Q4: What are the symptoms of incorrect scrub radius?
A: Poor straight-line stability, uneven tire wear, increased steering effort, or steering vibration.

Q5: How is scrub radius measured in practice?
A: Special alignment equipment is used to measure kingpin inclination and wheel parameters to calculate scrub radius.