October 9, 2015
The Basics of a Leaf Spring
Leaf Springs are one of the oldest forms of suspension dating back to medieval times. Some times referred to as a semi-elliptical spring or cart or carriage spring. The springs come in many forms and are mostly in a bowed shape made from flat spring steel. The center of the spring provides a location for the axle, while locating holes are provided on either end to be attached to the under side frame or chassis of the vesicle. Most leaf springs are made from several leaves stacked on top of each other, often with progressive shorter leaves located below the top leaf.
Lately manufacturers have introduced Parabolic springs, in this design, inter-leaf friction is unwanted, and therefore there is only contact between the spring at the ends and at the center where the axle is connected. This design is characterized by either only one leaf or fewer leaves whose thickness varies from center to ends following a parabolic curve. Aside from a weight saving, the main advantage of parabolic springs is their greater flexibility, which translates into vehicle ride quality approaching that of coil springs. However there is a trade-off in the form of reduced load carrying capability. The characteristic of parabolic springs is better riding comfort and not as “stiff” a ride as conventional “multi-leaf springs”. It is widely used on buses for better comfort.
The Solution to Your Axle Wrap Problem
The majority of pickup trucks have layered rear leaf springs, those with powerful engines producing additional toque, could have a problem with axle wrap and wheel hop. This occurs when the rotational force of the tires causes the axle housing to twist, during hard acceleration from a standing start. The twisting motion of the axle housing reacts to torque from engine forcing the springs to bend into an S-shape, this causes the tires to lose traction and jump, or hop. Once traction is lost the springs snap back into their original position. This happens over and over until the driver reduces torque input by letting off the throttle. The best way to eliminate axle wrap and wheel hop is by installing a Roadmaster Active Suspension (RAS) kit on the vehicle. The RAS supports the rear leaf springs in their optimum bowed position and prevents axle wrap and wheel hop from accruing.