Proper suspension geometry is critical to achieving proper vehicle feedback and performance, and even safety. Geometry is arguably more important than the quality of the parts installed, as CNC machined light weight control arms won’t be much benefit if they result in incorrect camber of king pin angle, and cause the vehicle to torque steer. The better approach is to understand what alignment and geometry you need for your intended use of the vehicle, and then install the necessary parts.
Another thing to consider is that the factory suspension geometry is not necessarily correct, or desired, especially on Vintage cars. This is why companies like Ride Tech have had success selling new geometry solutions for hot rods and muscle cars.
This video set describes the key considerations of suspension geometry perfectly.
You can view my new suspension install HERE to see the parts referenced in this video disassembled and in a real world application.
As an example, I’ll share the benefits I’ve seen of purchasing lowered spindles, custom control arms and an offset control arm shaft for the Dangerboat project.
The lowered front spindles allowed for a 2″ drop without changing the vehicles suspension. Simply cutting or shortening the front springs would have caused the front wheel to “swing” up into position, rather than simply moving the center of the hub up two inches, while leaving the control arms in the same location.
The control arms corrected a number of issues, including king pin angle, steering angle, and caster. From the factory, a 1970’s hotrod has terrible bump steer and steering geometry, and very little caster compared to modern standards. These control arms increased negating king pin angle, and increased caster, which improved cornering grip and stability, and also improved “return to center” feel of the car. The increased caster increased steering effort slightly, but also allowed the tires to lean into a corner (like a motorcycle) rather than out. They also changed the tie-rod mounting radius to reduce bump steer.
The offset upper control arm shaft allowed for more negative camber without the need for longer bolts or more shims. They also allowed for more caster alignment by allowing the front of the control arm to be pulled inward more relative to the rear of the control, which increases the angle that the front hub rotates on.
Most suspension designs and geometries have pro’s AND con’s, so its important to understand your goals and your car to achieve the right feel and performance!
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