If you own a first- or second-gen Camaro in particular, there are a plethora of suspension options from upgraded leaf spring rear, torque arm setup, 4-links and even independent suspension – to say nothing of the front. Chevelles and Tri-Fives are nearly as bountiful in their aftermarket suspension options. Which one is right for you is a discussion for another day, but today Suspension Geek is going to break down how these different setups actually change the way the car handles – and how – because of the “arc radius.”

If we go back to the good old days of geometry, a radius is a straight line from the center to the circumference of a circle. The circumference is the perimeter or the distance around the circle. The Suspension Geek illustration on both the dry erase board and the actual vehicles highlights how the radius arc works in varying designs and applications. Each component works in concert along this arc, or it doesn’t, and poor performance and other issues result.

A poorly designed radius arc in a vehicle’s suspension can significantly undermine both performance and drivability. When the arc traced by suspension components, such as control arms or radius rods, is not properly optimized, it can lead to a range of issues, including bump steer, where the wheels unintentionally change direction during suspension travel, resulting in twitchy handling. Excessive camber and toe changes during compression or rebound reduce tire contact with the road, compromising grip, cornering stability, and leading to uneven tire wear. Steering feel may also suffer from unwanted caster variation, making the vehicle unpredictable and less responsive. Additionally, poor arc geometry can limit usable suspension travel, contribute to a harsh ride, increase stress on driveline components, and accelerate wear on bushings and joints. Altogether, these issues not only affect safety and comfort but also diminish the overall handling precision expected from a well-engineered suspension system.

If you are wondering why control arms are angled a certain way, or why they are a certain length – hopefully this video illustrates exactly why.